Import 2.3.18pre1

[davej-history.git] / drivers / scsi / scsi_error.c

/*
 *  scsi_error.c Copyright (C) 1997 Eric Youngdale
 *
 *  SCSI error/timeout handling
 *      Initial versions: Eric Youngdale.  Based upon conversations with
 *                        Leonard Zubkoff and David Miller at Linux Expo, 
 *                        ideas originating from all over the place.
 *
 */

#define __NO_VERSION__
#include <linux/module.h>

#include <linux/sched.h>
#include <linux/timer.h>
#include <linux/string.h>
#include <linux/malloc.h>
#include <linux/ioport.h>
#include <linux/kernel.h>
#include <linux/stat.h>
#include <linux/blk.h>
#include <linux/interrupt.h>
#include <linux/delay.h>
#include <linux/smp_lock.h>

#define __KERNEL_SYSCALLS__

#include <linux/unistd.h>

#include <asm/system.h>
#include <asm/irq.h>
#include <asm/dma.h>

#include "scsi.h"
#include "hosts.h"
#include "constants.h"

#ifdef MODULE
#define SHUTDOWN_SIGS   (sigmask(SIGKILL)|sigmask(SIGINT)|sigmask(SIGTERM))
#else
#define SHUTDOWN_SIGS   (0UL)
#endif

#ifdef DEBUG
#define SENSE_TIMEOUT SCSI_TIMEOUT
#define ABORT_TIMEOUT SCSI_TIMEOUT
#define RESET_TIMEOUT SCSI_TIMEOUT
#else
#define SENSE_TIMEOUT (10*HZ)
#define RESET_TIMEOUT (2*HZ)
#define ABORT_TIMEOUT (15*HZ)
#endif

#define STATIC

/*
 * These should *probably* be handled by the host itself.
 * Since it is allowed to sleep, it probably should.
 */
#define BUS_RESET_SETTLE_TIME   5*HZ
#define HOST_RESET_SETTLE_TIME  10*HZ


static const char RCSid[] = "$Header: /mnt/ide/home/eric/CVSROOT/linux/drivers/scsi/scsi_error.c,v 1.10 1997/12/08 04:50:35 eric Exp $";

STATIC int scsi_check_sense(Scsi_Cmnd * SCpnt);
STATIC int scsi_request_sense(Scsi_Cmnd *);
STATIC void scsi_send_eh_cmnd(Scsi_Cmnd * SCpnt, int timeout);
STATIC int scsi_try_to_abort_command(Scsi_Cmnd *, int);
STATIC int scsi_test_unit_ready(Scsi_Cmnd *);
STATIC int scsi_try_bus_device_reset(Scsi_Cmnd *, int timeout);
STATIC int scsi_try_bus_reset(Scsi_Cmnd *);
STATIC int scsi_try_host_reset(Scsi_Cmnd *);
STATIC int scsi_unit_is_ready(Scsi_Cmnd *);
STATIC void scsi_eh_action_done(Scsi_Cmnd *, int);
STATIC int scsi_eh_retry_command(Scsi_Cmnd *);
STATIC int scsi_eh_completed_normally(Scsi_Cmnd * SCpnt);
STATIC void scsi_restart_operations(struct Scsi_Host *);
STATIC void scsi_eh_finish_command(Scsi_Cmnd ** SClist, Scsi_Cmnd * SCpnt);


/*
 * Function:    scsi_add_timer()
 *
 * Purpose:     Start timeout timer for a single scsi command.
 *
 * Arguments:   SCset   - command that is about to start running.
 *              timeout - amount of time to allow this command to run.
 *              complete - timeout function to call if timer isn't
 *                      canceled.
 *
 * Returns:     Nothing
 *
 * Notes:       This should be turned into an inline function.
 *
 * More Notes:  Each scsi command has it's own timer, and as it is added to
 *              the queue, we set up the timer.  When the command completes,
 *              we cancel the timer.  Pretty simple, really, especially
 *              compared to the old way of handling this crap.
 */
void scsi_add_timer(Scsi_Cmnd * SCset,
                    int timeout,
                    void (*complete) (Scsi_Cmnd *))
{

        /*
         * If the clock was already running for this command, then
         * first delete the timer.  The timer handling code gets rather
         * confused if we don't do this.
         */
        if (SCset->eh_timeout.function != NULL) {
                del_timer(&SCset->eh_timeout);
        }
        SCset->eh_timeout.data = (unsigned long) SCset;
        SCset->eh_timeout.expires = jiffies + timeout;
        SCset->eh_timeout.function = (void (*)(unsigned long)) complete;

        SCSI_LOG_ERROR_RECOVERY(5, printk("Adding timer for command %p at %d (%p)\n", SCset, timeout, complete));

        add_timer(&SCset->eh_timeout);

}

/*
 * Function:    scsi_delete_timer()
 *
 * Purpose:     Delete/cancel timer for a given function.
 *
 * Arguments:   SCset   - command that we are canceling timer for.
 *
 * Returns:     Amount of time remaining before command would have timed out.
 *
 * Notes:       This should be turned into an inline function.
 */
int scsi_delete_timer(Scsi_Cmnd * SCset)
{
        int rtn;

        rtn = jiffies - SCset->eh_timeout.expires;
        del_timer(&SCset->eh_timeout);

        SCSI_LOG_ERROR_RECOVERY(5, printk("Clearing timer for command %p\n", SCset));

        SCset->eh_timeout.data = (unsigned long) NULL;
        SCset->eh_timeout.function = NULL;

        return rtn;
}

/*
 * Function:    scsi_times_out()
 *
 * Purpose:     Timeout function for normal scsi commands..
 *
 * Arguments:   SCpnt   - command that is timing out.
 *
 * Returns:     Nothing.
 *
 * Notes:
 */
static void do_scsi_times_out(Scsi_Cmnd * SCpnt)
{

        /* 
         * Notify the low-level code that this operation failed and we are
         * reposessing the command.  
         */
#ifdef ERIC_neverdef
        /*
         * FIXME(eric)
         * Allow the host adapter to push a queue ordering tag
         * out to the bus to force the command in question to complete.
         * If the host wants to do this, then we just restart the timer
         * for the command.  Before we really do this, some real thought
         * as to the optimum way to handle this should be done.  We *do*
         * need to force ordering every so often to ensure that all requests
         * do eventually complete, but I am not sure if this is the best way
         * to actually go about it.
         *
         * Better yet, force a sync here, but don't block since we are in an
         * interrupt.
         */
        if (SCpnt->host->hostt->eh_ordered_queue_tag) {
                if ((*SCpnt->host->hostt->eh_ordered_queue_tag) (SCpnt)) {
                        scsi_add_timer(SCpnt, SCpnt->internal_timeout,
                                       scsi_times_out);
                        return;
                }
        }
        /*
         * FIXME(eric) - add a second special interface to handle this
         * case.  Ideally that interface can also be used to request
         * a queu
         */
        if (SCpnt->host->can_queue) {
                SCpnt->host->hostt->queuecommand(SCpnt, NULL);
        }
#endif

        /* Set the serial_number_at_timeout to the current serial_number */
        SCpnt->serial_number_at_timeout = SCpnt->serial_number;

        SCpnt->eh_state = FAILED;
        SCpnt->state = SCSI_STATE_TIMEOUT;
        SCpnt->owner = SCSI_OWNER_ERROR_HANDLER;

        SCpnt->host->in_recovery = 1;
        SCpnt->host->host_failed++;

        SCSI_LOG_TIMEOUT(3, printk("Command timed out active=%d busy=%d failed=%d\n",
                                   atomic_read(&SCpnt->host->host_active),
                                   SCpnt->host->host_busy,
                                   SCpnt->host->host_failed));

        /*
         * If the host is having troubles, then look to see if this was the last
         * command that might have failed.  If so, wake up the error handler.
         */
        if (SCpnt->host->host_busy == SCpnt->host->host_failed) {
                up(SCpnt->host->eh_wait);
        }
}

void scsi_times_out(Scsi_Cmnd * SCpnt)
{
        unsigned long flags;

        spin_lock_irqsave(&io_request_lock, flags);
        do_scsi_times_out(SCpnt);
        spin_unlock_irqrestore(&io_request_lock, flags);
}

/*
 * Function     scsi_block_when_processing_errors
 *
 * Purpose:     Prevent more commands from being queued while error recovery
 *              is taking place.
 *
 * Arguments:   SDpnt - device on which we are performing recovery.
 *
 * Returns:     FALSE   The device was taken offline by error recovery.
 *              TRUE    OK to proceed.
 *
 * Notes:       We block until the host is out of error recovery, and then
 *              check to see whether the host or the device is offline.
 */
int scsi_block_when_processing_errors(Scsi_Device * SDpnt)
{

        SCSI_SLEEP(&SDpnt->host->host_wait, SDpnt->host->in_recovery);

        SCSI_LOG_ERROR_RECOVERY(5, printk("Open returning %d\n", SDpnt->online));

        return SDpnt->online;
}

/*
 * Function:    scsi_eh_times_out()
 *
 * Purpose:     Timeout function for error handling.
 *
 * Arguments:   SCpnt   - command that is timing out.
 *
 * Returns:     Nothing.
 *
 * Notes:       During error handling, the kernel thread will be sleeping
 *              waiting for some action to complete on the device.  Our only
 *              job is to record that it timed out, and to wake up the
 *              thread.
 */
STATIC
void scsi_eh_times_out(Scsi_Cmnd * SCpnt)
{
        unsigned long flags;
        int rtn = FAILED;

        spin_lock_irqsave(&io_request_lock, flags);

        SCpnt->eh_state = SCSI_STATE_TIMEOUT;
        SCpnt->owner = SCSI_OWNER_LOWLEVEL;

        /*
         * As far as the low level driver is concerned, this command is still
         * active, so we must give the low level driver a chance to abort it. (DB)
         */
        if (SCpnt->host->hostt->eh_abort_handler)
                rtn = SCpnt->host->hostt->eh_abort_handler(SCpnt);

        SCpnt->request.rq_status = RQ_SCSI_DONE;
        SCpnt->owner = SCSI_OWNER_ERROR_HANDLER;

        SCSI_LOG_ERROR_RECOVERY(5, printk("In scsi_eh_times_out %p\n", SCpnt));

        if (SCpnt->host->eh_action != NULL)
                up(SCpnt->host->eh_action);
        else
                printk("Missing scsi error handler thread\n");
        spin_unlock_irqrestore(&io_request_lock, flags);
}


/*
 * Function:    scsi_eh_done()
 *
 * Purpose:     Completion function for error handling.
 *
 * Arguments:   SCpnt   - command that is timing out.
 *
 * Returns:     Nothing.
 *
 * Notes:       During error handling, the kernel thread will be sleeping
 *              waiting for some action to complete on the device.  Our only
 *              job is to record that the action completed, and to wake up the
 *              thread.
 */
STATIC
void scsi_eh_done(Scsi_Cmnd * SCpnt)
{
        SCpnt->request.rq_status = RQ_SCSI_DONE;

        SCpnt->owner = SCSI_OWNER_ERROR_HANDLER;
        SCpnt->eh_state = SUCCESS;

        SCSI_LOG_ERROR_RECOVERY(5, printk("In eh_done %p result:%x\n", SCpnt,
                                          SCpnt->result));

        if (SCpnt->host->eh_action != NULL)
                up(SCpnt->host->eh_action);
}

/*
 * Function:    scsi_eh_action_done()
 *
 * Purpose:     Completion function for error handling.
 *
 * Arguments:   SCpnt   - command that is timing out.
 *              answer  - boolean that indicates whether operation succeeded.
 *
 * Returns:     Nothing.
 *
 * Notes:       This callback is only used for abort and reset operations.
 */
STATIC
void scsi_eh_action_done(Scsi_Cmnd * SCpnt, int answer)
{
        SCpnt->request.rq_status = RQ_SCSI_DONE;

        SCpnt->owner = SCSI_OWNER_ERROR_HANDLER;
        SCpnt->eh_state = (answer ? SUCCESS : FAILED);

        if (SCpnt->host->eh_action != NULL)
                up(SCpnt->host->eh_action);
}

/*
 * Function:  scsi_sense_valid()
 *
 * Purpose:     Determine whether a host has automatically obtained sense
 *              information or not.  If we have it, then give a recommendation
 *              as to what we should do next.
 */
int scsi_sense_valid(Scsi_Cmnd * SCpnt)
{
        if (((SCpnt->sense_buffer[0] & 0x70) >> 4) != 7) {
                return FALSE;
        }
        return TRUE;
}

/*
 * Function:  scsi_eh_retry_command()
 *
 * Purpose:     Retry the original command
 *
 * Returns:     SUCCESS - we were able to get the sense data.
 *              FAILED  - we were not able to get the sense data.
 * 
 * Notes:       This function will *NOT* return until the command either
 *              times out, or it completes.
 */
STATIC int scsi_eh_retry_command(Scsi_Cmnd * SCpnt)
{
        memcpy((void *) SCpnt->cmnd, (void *) SCpnt->data_cmnd,
               sizeof(SCpnt->data_cmnd));
        SCpnt->request_buffer = SCpnt->buffer;
        SCpnt->request_bufflen = SCpnt->bufflen;
        SCpnt->use_sg = SCpnt->old_use_sg;
        SCpnt->cmd_len = SCpnt->old_cmd_len;

        scsi_send_eh_cmnd(SCpnt, SCpnt->timeout_per_command);

        /*
         * Hey, we are done.  Let's look to see what happened.
         */
        return SCpnt->eh_state;
}

/*
 * Function:  scsi_request_sense()
 *
 * Purpose:     Request sense data from a particular target.
 *
 * Returns:     SUCCESS - we were able to get the sense data.
 *              FAILED  - we were not able to get the sense data.
 * 
 * Notes:       Some hosts automatically obtain this information, others
 *              require that we obtain it on our own.
 *
 *              This function will *NOT* return until the command either
 *              times out, or it completes.
 */
STATIC int scsi_request_sense(Scsi_Cmnd * SCpnt)
{
        static unsigned char generic_sense[6] =
        {REQUEST_SENSE, 0, 0, 0, 255, 0};
        unsigned char scsi_result0[256], *scsi_result = NULL;


        memcpy((void *) SCpnt->cmnd, (void *) generic_sense,
               sizeof(generic_sense));

        SCpnt->cmnd[1] = SCpnt->lun << 5;

        scsi_result = (!SCpnt->host->hostt->unchecked_isa_dma)
            ? &scsi_result0[0] : scsi_init_malloc(512, GFP_ATOMIC | GFP_DMA);

        if (scsi_result == NULL) {
                printk("cannot allocate scsi_result in scsi_request_sense.\n");
                return FAILED;
        }
        /*
         * Zero the sense buffer.  Some host adapters automatically always request
         * sense, so it is not a good idea that SCpnt->request_buffer and
         * SCpnt->sense_buffer point to the same address (DB).
         * 0 is not a valid sense code. 
         */
        memset((void *) SCpnt->sense_buffer, 0, sizeof(SCpnt->sense_buffer));
        memset((void *) scsi_result, 0, 256);

        SCpnt->request_buffer = scsi_result;
        SCpnt->request_bufflen = 256;
        SCpnt->use_sg = 0;
        SCpnt->cmd_len = COMMAND_SIZE(SCpnt->cmnd[0]);

        scsi_send_eh_cmnd(SCpnt, SENSE_TIMEOUT);

        /* Last chance to have valid sense data */
        if (!scsi_sense_valid(SCpnt))
                memcpy((void *) SCpnt->sense_buffer,
                       SCpnt->request_buffer,
                       sizeof(SCpnt->sense_buffer));

        if (scsi_result != &scsi_result0[0] && scsi_result != NULL)
                scsi_init_free(scsi_result, 512);

        /*
         * When we eventually call scsi_finish, we really wish to complete
         * the original request, so let's restore the original data. (DB)
         */
        memcpy((void *) SCpnt->cmnd, (void *) SCpnt->data_cmnd,
               sizeof(SCpnt->data_cmnd));
        SCpnt->request_buffer = SCpnt->buffer;
        SCpnt->request_bufflen = SCpnt->bufflen;
        SCpnt->use_sg = SCpnt->old_use_sg;
        SCpnt->cmd_len = SCpnt->old_cmd_len;

        /*
         * Hey, we are done.  Let's look to see what happened.
         */
        return SCpnt->eh_state;
}

/*
 * Function:  scsi_test_unit_ready()
 *
 * Purpose:     Run test unit ready command to see if the device is talking to us or not.
 *
 */
STATIC int scsi_test_unit_ready(Scsi_Cmnd * SCpnt)
{
        static unsigned char tur_command[6] =
        {TEST_UNIT_READY, 0, 0, 0, 0, 0};
        unsigned char scsi_result0[256], *scsi_result = NULL;

        memcpy((void *) SCpnt->cmnd, (void *) tur_command,
               sizeof(tur_command));

        SCpnt->cmnd[1] = SCpnt->lun << 5;

        scsi_result = (!SCpnt->host->hostt->unchecked_isa_dma)
            ? &scsi_result0[0] : scsi_init_malloc(512, GFP_ATOMIC | GFP_DMA);

        if (scsi_result == NULL) {
                printk("cannot allocate scsi_result in scsi_test_unit_ready.\n");
                return FAILED;
        }
        /*
         * Zero the sense buffer.  Some host adapters automatically always request
         * sense, so it is not a good idea that SCpnt->request_buffer and
         * SCpnt->sense_buffer point to the same address (DB).
         * 0 is not a valid sense code. 
         */
        memset((void *) SCpnt->sense_buffer, 0, sizeof(SCpnt->sense_buffer));
        memset((void *) scsi_result, 0, 256);

        SCpnt->request_buffer = scsi_result;
        SCpnt->request_bufflen = 256;
        SCpnt->use_sg = 0;
        SCpnt->cmd_len = COMMAND_SIZE(SCpnt->cmnd[0]);
        scsi_send_eh_cmnd(SCpnt, SENSE_TIMEOUT);

        /* Last chance to have valid sense data */
        if (!scsi_sense_valid(SCpnt))
                memcpy((void *) SCpnt->sense_buffer,
                       SCpnt->request_buffer,
                       sizeof(SCpnt->sense_buffer));

        if (scsi_result != &scsi_result0[0] && scsi_result != NULL)
                scsi_init_free(scsi_result, 512);

        /*
         * When we eventually call scsi_finish, we really wish to complete
         * the original request, so let's restore the original data. (DB)
         */
        memcpy((void *) SCpnt->cmnd, (void *) SCpnt->data_cmnd,
               sizeof(SCpnt->data_cmnd));
        SCpnt->request_buffer = SCpnt->buffer;
        SCpnt->request_bufflen = SCpnt->bufflen;
        SCpnt->use_sg = SCpnt->old_use_sg;
        SCpnt->cmd_len = SCpnt->old_cmd_len;

        /*
         * Hey, we are done.  Let's look to see what happened.
         */
        return SCpnt->eh_state;
}

/*
 * This would normally need to get the IO request lock,
 * but as it doesn't actually touch anything that needs
 * to be locked we can avoid the lock here..
 */
STATIC
void scsi_sleep_done(struct semaphore *sem)
{
        if (sem != NULL) {
                up(sem);
        }
}


void scsi_sleep(int timeout)
{
        DECLARE_MUTEX_LOCKED(sem);
        struct timer_list timer;

        init_timer(&timer);
        timer.data = (unsigned long) &sem;
        timer.expires = jiffies + timeout;
        timer.function = (void (*)(unsigned long)) scsi_sleep_done;

        SCSI_LOG_ERROR_RECOVERY(5, printk("Sleeping for timer tics %d\n", timeout));

        add_timer(&timer);

        spin_unlock_irq(&io_request_lock);
        down(&sem);
        spin_lock_irq(&io_request_lock);

        del_timer(&timer);
}

/*
 * Function:  scsi_send_eh_cmnd
 *
 * Purpose:     Send a command out to a device as part of error recovery.
 *
 * Notes:       The initialization of the structures is quite a bit different
 *              in this case, and furthermore, there is a different completion
 *              handler.
 */
STATIC void scsi_send_eh_cmnd(Scsi_Cmnd * SCpnt, int timeout)
{
        struct Scsi_Host *host;

        host = SCpnt->host;

      retry:
        /*
         * We will use a queued command if possible, otherwise we will emulate the
         * queuing and calling of completion function ourselves.
         */
        SCpnt->owner = SCSI_OWNER_LOWLEVEL;

        if (host->can_queue) {
                DECLARE_MUTEX_LOCKED(sem);

                SCpnt->eh_state = SCSI_STATE_QUEUED;

                scsi_add_timer(SCpnt, timeout, scsi_eh_times_out);

                /*
                 * Set up the semaphore so we wait for the command to complete.
                 */
                SCpnt->host->eh_action = &sem;
                SCpnt->request.rq_status = RQ_SCSI_BUSY;

                host->hostt->queuecommand(SCpnt, scsi_eh_done);
                spin_unlock_irq(&io_request_lock);
                down(&sem);
                spin_lock_irq(&io_request_lock);

                SCpnt->host->eh_action = NULL;

                del_timer(&SCpnt->eh_timeout);

                /*
                 * See if timeout.  If so, tell the host to forget about it.
                 * In other words, we don't want a callback any more.
                 */
                if (SCpnt->eh_state == SCSI_STATE_TIMEOUT) {
                        SCpnt->eh_state = FAILED;
                }
                SCSI_LOG_ERROR_RECOVERY(5, printk("send_eh_cmnd: %p eh_state:%x\n",
                                                SCpnt, SCpnt->eh_state));
        } else {
                int temp;

                /*
                 * We damn well had better never use this code.  There is no timeout
                 * protection here, since we would end up waiting in the actual low
                 * level driver, we don't know how to wake it up.
                 */
                temp = host->hostt->command(SCpnt);
                SCpnt->result = temp;
                if (scsi_eh_completed_normally(SCpnt)) {
                        SCpnt->eh_state = SUCCESS;
                } else {
                        SCpnt->eh_state = FAILED;
                }
        }

        /*
         * Now examine the actual status codes to see whether the command actually
         * did complete normally.
         */
        if (SCpnt->eh_state == SUCCESS) {
                switch (scsi_eh_completed_normally(SCpnt)) {
                case SUCCESS:
                        SCpnt->eh_state = SUCCESS;
                        break;
                case NEEDS_RETRY:
                        goto retry;
                case FAILED:
                default:
                        SCpnt->eh_state = FAILED;
                        break;
                }
        } else {
                SCpnt->eh_state = FAILED;
        }
}

/*
 * Function:  scsi_unit_is_ready()
 *
 * Purpose:     Called after TEST_UNIT_READY is run, to test to see if
 *              the unit responded in a way that indicates it is ready.
 */
STATIC int scsi_unit_is_ready(Scsi_Cmnd * SCpnt)
{
        if (SCpnt->result) {
                if (((driver_byte(SCpnt->result) & DRIVER_SENSE) ||
                     (status_byte(SCpnt->result) & CHECK_CONDITION)) &&
                    ((SCpnt->sense_buffer[0] & 0x70) >> 4) == 7) {
                        if (((SCpnt->sense_buffer[2] & 0xf) != NOT_READY) &&
                            ((SCpnt->sense_buffer[2] & 0xf) != UNIT_ATTENTION) &&
                            ((SCpnt->sense_buffer[2] & 0xf) != ILLEGAL_REQUEST)) {
                                return 0;
                        }
                }
        }
        return 1;
}

/*
 * Function:    scsi_eh_finish_command
 *
 * Purpose:     Handle a command that we are finished with WRT error handling.
 *
 * Arguments:   SClist - pointer to list into which we are putting completed commands.
 *              SCpnt  - command that is completing
 *
 * Notes:       We don't want to use the normal command completion while we are
 *              are still handling errors - it may cause other commands to be queued,
 *              and that would disturb what we are doing.  Thus we really want to keep
 *              a list of pending commands for final completion, and once we
 *              are ready to leave error handling we handle completion for real.
 */
STATIC void scsi_eh_finish_command(Scsi_Cmnd ** SClist, Scsi_Cmnd * SCpnt)
{
        SCpnt->state = SCSI_STATE_BHQUEUE;
        SCpnt->bh_next = *SClist;
        /*
         * Set this back so that the upper level can correctly free up
         * things.
         */
        SCpnt->use_sg = SCpnt->old_use_sg;
        *SClist = SCpnt;
}

/*
 * Function:  scsi_try_to_abort_command
 *
 * Purpose:     Ask host adapter to abort a running command.
 *
 * Returns:     FAILED          Operation failed or not supported.
 *              SUCCESS         Succeeded.
 *
 * Notes:       This function will not return until the user's completion
 *              function has been called.  There is no timeout on this
 *              operation.  If the author of the low-level driver wishes
 *              this operation to be timed, they can provide this facility
 *              themselves.  Helper functions in scsi_error.c can be supplied
 *              to make this easier to do.
 *
 * Notes:       It may be possible to combine this with all of the reset
 *              handling to eliminate a lot of code duplication.  I don't
 *              know what makes more sense at the moment - this is just a
 *              prototype.
 */
STATIC int scsi_try_to_abort_command(Scsi_Cmnd * SCpnt, int timeout)
{
        SCpnt->eh_state = FAILED;       /* Until we come up with something better */

        if (SCpnt->host->hostt->eh_abort_handler == NULL) {
                return FAILED;
        }
        /* 
         * scsi_done was called just after the command timed out and before
         * we had a chance to process it. (DB)
         */
        if (SCpnt->serial_number == 0)
                return SUCCESS;

        SCpnt->owner = SCSI_OWNER_LOWLEVEL;

        return SCpnt->host->hostt->eh_abort_handler(SCpnt);
}

/*
 * Function:  scsi_try_bus_device_reset
 *
 * Purpose:     Ask host adapter to perform a bus device reset for a given
 *              device.
 *
 * Returns:     FAILED          Operation failed or not supported.
 *              SUCCESS         Succeeded.
 *
 * Notes:       There is no timeout for this operation.  If this operation is
 *              unreliable for a given host, then the host itself needs to put a
 *              timer on it, and set the host back to a consistent state prior
 *              to returning.
 */
STATIC int scsi_try_bus_device_reset(Scsi_Cmnd * SCpnt, int timeout)
{
        int rtn;

        SCpnt->eh_state = FAILED;       /* Until we come up with something better */

        if (SCpnt->host->hostt->eh_device_reset_handler == NULL) {
                return FAILED;
        }
        SCpnt->owner = SCSI_OWNER_LOWLEVEL;

        rtn = SCpnt->host->hostt->eh_device_reset_handler(SCpnt);

        if (rtn == SUCCESS)
                SCpnt->eh_state = SUCCESS;

        return SCpnt->eh_state;
}

/*
 * Function:  scsi_try_bus_reset
 *
 * Purpose:     Ask host adapter to perform a bus reset for a host.
 *
 * Returns:     FAILED          Operation failed or not supported.
 *              SUCCESS         Succeeded.
 *
 * Notes:       
 */
STATIC int scsi_try_bus_reset(Scsi_Cmnd * SCpnt)
{
        int rtn;

        SCpnt->eh_state = FAILED;       /* Until we come up with something better */
        SCpnt->owner = SCSI_OWNER_LOWLEVEL;
        SCpnt->serial_number_at_timeout = SCpnt->serial_number;

        if (SCpnt->host->hostt->eh_bus_reset_handler == NULL) {
                return FAILED;
        }
        rtn = SCpnt->host->hostt->eh_bus_reset_handler(SCpnt);

        if (rtn == SUCCESS)
                SCpnt->eh_state = SUCCESS;

        /*
         * If we had a successful bus reset, mark the command blocks to expect
         * a condition code of unit attention.
         */
        scsi_sleep(BUS_RESET_SETTLE_TIME);
        if (SCpnt->eh_state == SUCCESS) {
                Scsi_Device *SDloop;
                for (SDloop = SCpnt->host->host_queue; SDloop; SDloop = SDloop->next) {
                        if (SCpnt->channel == SDloop->channel) {
                                SDloop->was_reset = 1;
                                SDloop->expecting_cc_ua = 1;
                        }
                }
        }
        return SCpnt->eh_state;
}

/*
 * Function:  scsi_try_host_reset
 *
 * Purpose:     Ask host adapter to reset itself, and the bus.
 *
 * Returns:     FAILED          Operation failed or not supported.
 *              SUCCESS         Succeeded.
 *
 * Notes:
 */
STATIC int scsi_try_host_reset(Scsi_Cmnd * SCpnt)
{
        int rtn;

        SCpnt->eh_state = FAILED;       /* Until we come up with something better */
        SCpnt->owner = SCSI_OWNER_LOWLEVEL;
        SCpnt->serial_number_at_timeout = SCpnt->serial_number;

        if (SCpnt->host->hostt->eh_host_reset_handler == NULL) {
                return FAILED;
        }
        rtn = SCpnt->host->hostt->eh_host_reset_handler(SCpnt);

        if (rtn == SUCCESS)
                SCpnt->eh_state = SUCCESS;

        /*
         * If we had a successful host reset, mark the command blocks to expect
         * a condition code of unit attention.
         */
        scsi_sleep(HOST_RESET_SETTLE_TIME);
        if (SCpnt->eh_state == SUCCESS) {
                Scsi_Device *SDloop;
                for (SDloop = SCpnt->host->host_queue; SDloop; SDloop = SDloop->next) {
                        SDloop->was_reset = 1;
                        SDloop->expecting_cc_ua = 1;
                }
        }
        return SCpnt->eh_state;
}

/*
 * Function:  scsi_decide_disposition
 *
 * Purpose:     Examine a command block that has come back from the low-level
 *              and figure out what to do next.
 *
 * Returns:     SUCCESS         - pass on to upper level.
 *              FAILED          - pass on to error handler thread.
 *              RETRY           - command should be retried.
 *              SOFTERR         - command succeeded, but we need to log
 *                                a soft error.
 *
 * Notes:       This is *ONLY* called when we are examining the status
 *              after sending out the actual data command.  Any commands
 *              that are queued for error recovery (i.e. TEST_UNIT_READY)
 *              do *NOT* come through here.
 *
 *              NOTE - When this routine returns FAILED, it means the error
 *              handler thread is woken.  In cases where the error code
 *              indicates an error that doesn't require the error handler
 *              thread (i.e. we don't need to abort/reset), then this function
 *              should return SUCCESS.
 */
int scsi_decide_disposition(Scsi_Cmnd * SCpnt)
{
        int rtn;

        /*
         * If the device is offline, then we clearly just pass the result back
         * up to the top level.
         */
        if (SCpnt->device->online == FALSE) {
                SCSI_LOG_ERROR_RECOVERY(5, printk("scsi_error.c: device offline - report as SUCCESS\n"));
                return SUCCESS;
        }
        /*
         * First check the host byte, to see if there is anything in there
         * that would indicate what we need to do.
         */

        switch (host_byte(SCpnt->result)) {
        case DID_PASSTHROUGH:
                /*
                 * No matter what, pass this through to the upper layer.
                 * Nuke this special code so that it looks like we are saying
                 * DID_OK.
                 */
                SCpnt->result &= 0xff00ffff;
                return SUCCESS;
        case DID_OK:
                /*
                 * Looks good.  Drop through, and check the next byte.
                 */
                break;
        case DID_NO_CONNECT:
        case DID_BAD_TARGET:
        case DID_ABORT:
                /*
                 * Note - this means that we just report the status back to the
                 * top level driver, not that we actually think that it indicates
                 * success.
                 */
                return SUCCESS;
                /*
                 * When the low level driver returns DID_SOFT_ERROR,
                 * it is responsible for keeping an internal retry counter 
                 * in order to avoid endless loops (DB)
                 */
        case DID_SOFT_ERROR:
                return NEEDS_RETRY;

        case DID_BUS_BUSY:
        case DID_PARITY:
        case DID_ERROR:
                goto maybe_retry;
        case DID_TIME_OUT:
                /*
                   * When we scan the bus, we get timeout messages for
                   * these commands if there is no device available.
                   * Other hosts report DID_NO_CONNECT for the same thing.
                 */
                if ((SCpnt->cmnd[0] == TEST_UNIT_READY ||
                     SCpnt->cmnd[0] == INQUIRY)) {
                        return SUCCESS;
                } else {
                        return FAILED;
                }
        case DID_RESET:
                /*
                 * In the normal case where we haven't initiated a reset, this is
                 * a failure.
                 */
                if (SCpnt->flags & IS_RESETTING) {
                        SCpnt->flags &= ~IS_RESETTING;
                        goto maybe_retry;
                }
                /*
                 * Examine the sense data to figure out how to proceed from here.
                 * If there is no sense data, we will be forced into the error
                 * handler thread, where we get to examine the thing in a lot more
                 * detail.
                 */
                return scsi_check_sense(SCpnt);
        default:
                return FAILED;
        }

        /*
         * Next, check the message byte.
         */
        if (msg_byte(SCpnt->result) != COMMAND_COMPLETE) {
                return FAILED;
        }
        /*
         * Now, check the status byte to see if this indicates anything special.
         */
        switch (status_byte(SCpnt->result)) {
        case QUEUE_FULL:
                /*
                 * The case of trying to send too many commands to a tagged queueing
                 * device.
                 */
                return ADD_TO_MLQUEUE;
        case GOOD:
        case COMMAND_TERMINATED:
                return SUCCESS;
        case CHECK_CONDITION:
                rtn = scsi_check_sense(SCpnt);
                if (rtn == NEEDS_RETRY) {
                        goto maybe_retry;
                }
                return rtn;
        case CONDITION_GOOD:
        case INTERMEDIATE_GOOD:
        case INTERMEDIATE_C_GOOD:
                /*
                 * Who knows?  FIXME(eric)
                 */
                return SUCCESS;
        case BUSY:
        case RESERVATION_CONFLICT:
                goto maybe_retry;
        default:
                return FAILED;
        }
        return FAILED;

      maybe_retry:

        if ((++SCpnt->retries) < SCpnt->allowed) {
                return NEEDS_RETRY;
        } else {
                return FAILED;
        }
}

/*
 * Function:  scsi_eh_completed_normally
 *
 * Purpose:     Examine a command block that has come back from the low-level
 *              and figure out what to do next.
 *
 * Returns:     SUCCESS         - pass on to upper level.
 *              FAILED          - pass on to error handler thread.
 *              RETRY           - command should be retried.
 *              SOFTERR         - command succeeded, but we need to log
 *                                a soft error.
 *
 * Notes:       This is *ONLY* called when we are examining the status
 *              of commands queued during error recovery.  The main
 *              difference here is that we don't allow for the possibility
 *              of retries here, and we are a lot more restrictive about what
 *              we consider acceptable.
 */
STATIC int scsi_eh_completed_normally(Scsi_Cmnd * SCpnt)
{
        int rtn;
        /*
         * First check the host byte, to see if there is anything in there
         * that would indicate what we need to do.
         */
        if (host_byte(SCpnt->result) == DID_RESET) {
                if (SCpnt->flags & IS_RESETTING) {
                        /*
                         * OK, this is normal.  We don't know whether in fact the
                         * command in question really needs to be rerun or not - 
                         * if this was the original data command then the answer is yes,
                         * otherwise we just flag it as success.
                         */
                        SCpnt->flags &= ~IS_RESETTING;
                        return NEEDS_RETRY;
                }
                /*
                 * Rats.  We are already in the error handler, so we now get to try
                 * and figure out what to do next.  If the sense is valid, we have
                 * a pretty good idea of what to do.  If not, we mark it as failed.
                 */
                return scsi_check_sense(SCpnt);
        }
        if (host_byte(SCpnt->result) != DID_OK) {
                return FAILED;
        }
        /*
         * Next, check the message byte.
         */
        if (msg_byte(SCpnt->result) != COMMAND_COMPLETE) {
                return FAILED;
        }
        /*
         * Now, check the status byte to see if this indicates anything special.
         */
        switch (status_byte(SCpnt->result)) {
        case GOOD:
        case COMMAND_TERMINATED:
                return SUCCESS;
        case CHECK_CONDITION:
                rtn = scsi_check_sense(SCpnt);
                if (rtn == NEEDS_RETRY) {
                        return FAILED;
                }
                return rtn;
        case CONDITION_GOOD:
        case INTERMEDIATE_GOOD:
        case INTERMEDIATE_C_GOOD:
                /*
                 * Who knows?  FIXME(eric)
                 */
                return SUCCESS;
        case BUSY:
        case QUEUE_FULL:
        case RESERVATION_CONFLICT:
        default:
                return FAILED;
        }
        return FAILED;
}

/*
 * Function:  scsi_check_sense
 *
 * Purpose:     Examine sense information - give suggestion as to what
 *              we should do with it.
 */
STATIC int scsi_check_sense(Scsi_Cmnd * SCpnt)
{
        if (!scsi_sense_valid(SCpnt)) {
                return FAILED;
        }
        if (SCpnt->sense_buffer[2] & 0xe0)
                return SUCCESS;

        switch (SCpnt->sense_buffer[2] & 0xf) {
        case NO_SENSE:
                return SUCCESS;
        case RECOVERED_ERROR:
                return /* SOFT_ERROR */ SUCCESS;

        case ABORTED_COMMAND:
                return NEEDS_RETRY;
        case NOT_READY:
        case UNIT_ATTENTION:
                /*
                 * If we are expecting a CC/UA because of a bus reset that we
                 * performed, treat this just as a retry.  Otherwise this is
                 * information that we should pass up to the upper-level driver
                 * so that we can deal with it there.
                 */
                if (SCpnt->device->expecting_cc_ua) {
                        SCpnt->device->expecting_cc_ua = 0;
                        return NEEDS_RETRY;
                }
                return SUCCESS;

                /* these three are not supported */
        case COPY_ABORTED:
        case VOLUME_OVERFLOW:
        case MISCOMPARE:
                return SUCCESS;

        case MEDIUM_ERROR:
                return NEEDS_RETRY;

        case ILLEGAL_REQUEST:
        case BLANK_CHECK:
        case DATA_PROTECT:
        case HARDWARE_ERROR:
        default:
                return SUCCESS;
        }
}


/*
 * Function:  scsi_restart_operations
 *
 * Purpose:     Restart IO operations to the specified host.
 *
 * Arguments:   host  - host that we are restarting
 *
 * Returns:     Nothing
 *
 * Notes:       When we entered the error handler, we blocked all further
 *              I/O to this device.  We need to 'reverse' this process.
 */
STATIC void scsi_restart_operations(struct Scsi_Host *host)
{
        Scsi_Device *SDpnt;

        /*
         * Next free up anything directly waiting upon the host.  This will be
         * requests for character device operations, and also for ioctls to queued
         * block devices.
         */
        SCSI_LOG_ERROR_RECOVERY(5, printk("scsi_error.c: Waking up host to restart\n"));

        wake_up(&host->host_wait);

        /*
         * Finally, block devices need an extra kick in the pants.  This is because
         * the request queueing mechanism may have queued lots of pending requests
         * and there won't be a process waiting in a place where we can simply wake
         * it up.  Thus we simply go through and call the request function to goose
         * the various top level drivers and get things moving again.
         */
        for (SDpnt = host->host_queue; SDpnt; SDpnt = SDpnt->next) {
                SCSI_LOG_ERROR_RECOVERY(5, printk("Calling request function to restart things...\n"));

                if (SDpnt->scsi_request_fn != NULL)
                        (*SDpnt->scsi_request_fn) ();
        }
}

/*
 * Function:  scsi_unjam_host
 *
 * Purpose:     Attempt to fix a host which has a command that failed for
 *              some reason.
 *
 * Arguments:   host    - host that needs unjamming.
 * 
 * Returns:     Nothing
 *
 * Notes:       When we come in here, we *know* that all commands on the
 *              bus have either completed, failed or timed out.  We also
 *              know that no further commands are being sent to the host,
 *              so things are relatively quiet and we have freedom to
 *              fiddle with things as we wish.
 *
 * Additional note:  This is only the *default* implementation.  It is possible
 *              for individual drivers to supply their own version of this
 *              function, and if the maintainer wishes to do this, it is
 *              strongly suggested that this function be taken as a template
 *              and modified.  This function was designed to correctly handle
 *              problems for about 95% of the different cases out there, and
 *              it should always provide at least a reasonable amount of error
 *              recovery.
 *
 * Note3:       Any command marked 'FAILED' or 'TIMEOUT' must eventually
 *              have scsi_finish_command() called for it.  We do all of
 *              the retry stuff here, so when we restart the host after we
 *              return it should have an empty queue.
 */
STATIC int scsi_unjam_host(struct Scsi_Host *host)
{
        int devices_failed;
        int numfailed;
        int ourrtn;
        int rtn = FALSE;
        int result;
        Scsi_Cmnd *SCloop;
        Scsi_Cmnd *SCpnt;
        Scsi_Device *SDpnt;
        Scsi_Device *SDloop;
        Scsi_Cmnd *SCdone;
        int timed_out;

        SCdone = NULL;

        /*
         * First, protect against any sort of race condition.  If any of the outstanding
         * commands are in states that indicate that we are not yet blocked (i.e. we are
         * not in a quiet state) then we got woken up in error.  If we ever end up here,
         * we need to re-examine some of the assumptions.
         */
        for (SDpnt = host->host_queue; SDpnt; SDpnt = SDpnt->next) {
                for (SCpnt = SDpnt->device_queue; SCpnt; SCpnt = SCpnt->next) {
                        if (SCpnt->state == SCSI_STATE_FAILED
                            || SCpnt->state == SCSI_STATE_TIMEOUT
                            || SCpnt->state == SCSI_STATE_INITIALIZING
                            || SCpnt->state == SCSI_STATE_UNUSED) {
                                continue;
                        }
                        /*
                         * Rats.  Something is still floating around out there.  This could
                         * be the result of the fact that the upper level drivers are still frobbing
                         * commands that might have succeeded.  There are two outcomes.  One is that
                         * the command block will eventually be freed, and the other one is that
                         * the command will be queued and will be finished along the way.
                         */
                        SCSI_LOG_ERROR_RECOVERY(1, printk("Error handler prematurely woken - commands still active (%p %x %d)\n", SCpnt, SCpnt->state, SCpnt->target));

/*
 *        panic("SCSI Error handler woken too early\n");
 *
 * This is no longer a problem, since now the code cares only about
 * SCSI_STATE_TIMEOUT and SCSI_STATE_FAILED.
 * Other states are useful only to release active commands when devices are
 * set offline. If (host->host_active == host->host_busy) we can safely assume
 * that there are no commands in state other then TIMEOUT od FAILED. (DB)
 *
 * FIXME:
 * It is not easy to release correctly commands according to their state when 
 * devices are set offline, when the state is neither TIMEOUT nor FAILED.
 * When a device is set offline, we can have some command with
 * rq_status=RQ_SCSY_BUSY, owner=SCSI_STATE_HIGHLEVEL, 
 * state=SCSI_STATE_INITIALIZING and the driver module cannot be released.
 * (DB, 17 May 1998)
 */
                }
        }

        /*
         * Next, see if we need to request sense information.  if so,
         * then get it now, so we have a better idea of what to do.
         * FIXME(eric) this has the unfortunate side effect that if a host
         * adapter does not automatically request sense information, that we end
         * up shutting it down before we request it.  All hosts should be doing this
         * anyways, so for now all I have to say is tough noogies if you end up in here.
         * On second thought, this is probably a good idea.  We *really* want to give
         * authors an incentive to automatically request this.
         */
        SCSI_LOG_ERROR_RECOVERY(3, printk("scsi_unjam_host: Checking to see if we need to request sense\n"));

        for (SDpnt = host->host_queue; SDpnt; SDpnt = SDpnt->next) {
                for (SCpnt = SDpnt->device_queue; SCpnt; SCpnt = SCpnt->next) {
                        if (SCpnt->state != SCSI_STATE_FAILED || scsi_sense_valid(SCpnt)) {
                                continue;
                        }
                        SCSI_LOG_ERROR_RECOVERY(2, printk("scsi_unjam_host: Requesting sense for %d\n",
                                                          SCpnt->target));
                        rtn = scsi_request_sense(SCpnt);
                        if (rtn != SUCCESS) {
                                continue;
                        }
                        SCSI_LOG_ERROR_RECOVERY(3, printk("Sense requested for %p - result %x\n",
                                                  SCpnt, SCpnt->result));
                        SCSI_LOG_ERROR_RECOVERY(3, print_sense("bh", SCpnt));

                        result = scsi_decide_disposition(SCpnt);

                        /*
                         * If the result was normal, then just pass it along to the
                         * upper level.
                         */
                        if (result == SUCCESS) {
                                SCpnt->host->host_failed--;
                                scsi_eh_finish_command(&SCdone, SCpnt);
                        }
                        if (result != NEEDS_RETRY) {
                                continue;
                        }
                        /* 
                         * We only come in here if we want to retry a
                         * command.  The test to see whether the command
                         * should be retried should be keeping track of the
                         * number of tries, so we don't end up looping, of
                         * course.  
                         */
                        SCpnt->state = NEEDS_RETRY;
                        rtn = scsi_eh_retry_command(SCpnt);
                        if (rtn != SUCCESS) {
                                continue;
                        }
                        /*
                         * We eventually hand this one back to the top level.
                         */
                        SCpnt->host->host_failed--;
                        scsi_eh_finish_command(&SCdone, SCpnt);
                }
        }

        /*
         * Go through the list of commands and figure out where we stand and how bad things
         * really are.
         */
        numfailed = 0;
        timed_out = 0;
        devices_failed = 0;
        for (SDpnt = host->host_queue; SDpnt; SDpnt = SDpnt->next) {
                unsigned int device_error = 0;

                for (SCpnt = SDpnt->device_queue; SCpnt; SCpnt = SCpnt->next) {
                        if (SCpnt->state == SCSI_STATE_FAILED) {
                                SCSI_LOG_ERROR_RECOVERY(5, printk("Command to ID %d failed\n",
                                                         SCpnt->target));
                                numfailed++;
                                device_error++;
                        }
                        if (SCpnt->state == SCSI_STATE_TIMEOUT) {
                                SCSI_LOG_ERROR_RECOVERY(5, printk("Command to ID %d timedout\n",
                                                         SCpnt->target));
                                timed_out++;
                                device_error++;
                        }
                }
                if (device_error > 0) {
                        devices_failed++;
                }
        }

        SCSI_LOG_ERROR_RECOVERY(2, printk("Total of %d+%d commands on %d devices require eh work\n",
                                  numfailed, timed_out, devices_failed));

        if (host->host_failed == 0) {
                ourrtn = TRUE;
                goto leave;
        }
        /*
         * Next, try and see whether or not it makes sense to try and abort
         * the running command.  This only works out to be the case if we have
         * one command that has timed out.  If the command simply failed, it
         * makes no sense to try and abort the command, since as far as the
         * host adapter is concerned, it isn't running.
         */

        SCSI_LOG_ERROR_RECOVERY(3, printk("scsi_unjam_host: Checking to see if we want to try abort\n"));

        for (SDpnt = host->host_queue; SDpnt; SDpnt = SDpnt->next) {
                for (SCloop = SDpnt->device_queue; SCloop; SCloop = SCloop->next) {
                        if (SCloop->state != SCSI_STATE_TIMEOUT) {
                                continue;
                        }
                        rtn = scsi_try_to_abort_command(SCloop, ABORT_TIMEOUT);
                        if (rtn == SUCCESS) {
                                rtn = scsi_test_unit_ready(SCloop);

                                if (rtn == SUCCESS && scsi_unit_is_ready(SCloop)) {
                                        rtn = scsi_eh_retry_command(SCloop);

                                        if (rtn == SUCCESS) {
                                                SCloop->host->host_failed--;
                                                scsi_eh_finish_command(&SCdone, SCloop);
                                        }
                                }
                        }
                }
        }

        /*
         * If we have corrected all of the problems, then we are done.
         */
        if (host->host_failed == 0) {
                ourrtn = TRUE;
                goto leave;
        }
        /*
         * Either the abort wasn't appropriate, or it didn't succeed.
         * Now try a bus device reset.  Still, look to see whether we have
         * multiple devices that are jammed or not - if we have multiple devices,
         * it makes no sense to try BUS_DEVICE_RESET - we really would need
         * to try a BUS_RESET instead.
         *
         * Does this make sense - should we try BDR on each device individually?
         * Yes, definitely.
         */
        SCSI_LOG_ERROR_RECOVERY(3, printk("scsi_unjam_host: Checking to see if we want to try BDR\n"));

        for (SDpnt = host->host_queue; SDpnt; SDpnt = SDpnt->next) {
                for (SCloop = SDpnt->device_queue; SCloop; SCloop = SCloop->next) {
                        if (SCloop->state == SCSI_STATE_FAILED
                            || SCloop->state == SCSI_STATE_TIMEOUT) {
                                break;
                        }
                }

                if (SCloop == NULL) {
                        continue;
                }
                /*
                 * OK, we have a device that is having problems.  Try and send
                 * a bus device reset to it.
                 *
                 * FIXME(eric) - make sure we handle the case where multiple
                 * commands to the same device have failed. They all must
                 * get properly restarted.
                 */
                rtn = scsi_try_bus_device_reset(SCloop, RESET_TIMEOUT);

                if (rtn == SUCCESS) {
                        rtn = scsi_test_unit_ready(SCloop);

                        if (rtn == SUCCESS && scsi_unit_is_ready(SCloop)) {
                                rtn = scsi_eh_retry_command(SCloop);

                                if (rtn == SUCCESS) {
                                        SCloop->host->host_failed--;
                                        scsi_eh_finish_command(&SCdone, SCloop);
                                }
                        }
                }
        }

        if (host->host_failed == 0) {
                ourrtn = TRUE;
                goto leave;
        }
        /*
         * If we ended up here, we have serious problems.  The only thing left
         * to try is a full bus reset.  If someone has grabbed the bus and isn't
         * letting go, then perhaps this will help.
         */
        SCSI_LOG_ERROR_RECOVERY(3, printk("scsi_unjam_host: Try hard bus reset\n"));

        /* 
         * We really want to loop over the various channels, and do this on
         * a channel by channel basis.  We should also check to see if any
         * of the failed commands are on soft_reset devices, and if so, skip
         * the reset.  
         */
        for (SDpnt = host->host_queue; SDpnt; SDpnt = SDpnt->next) {
              next_device:
                for (SCpnt = SDpnt->device_queue; SCpnt; SCpnt = SCpnt->next) {
                        if (SCpnt->state != SCSI_STATE_FAILED
                            && SCpnt->state != SCSI_STATE_TIMEOUT) {
                                continue;
                        }
                        /*
                         * We have a failed command.  Make sure there are no other failed
                         * commands on the same channel that are timed out and implement a
                         * soft reset.
                         */
                        for (SDloop = host->host_queue; SDloop; SDloop = SDloop->next) {
                                for (SCloop = SDloop->device_queue; SCloop; SCloop = SCloop->next) {
                                        if (SCloop->channel != SCpnt->channel) {
                                                continue;
                                        }
                                        if (SCloop->state != SCSI_STATE_FAILED
                                            && SCloop->state != SCSI_STATE_TIMEOUT) {
                                                continue;
                                        }
                                        if (SDloop->soft_reset && SCloop->state == SCSI_STATE_TIMEOUT) {
                                                /* 
                                                 * If this device uses the soft reset option, and this
                                                 * is one of the devices acting up, then our only
                                                 * option is to wait a bit, since the command is
                                                 * supposedly still running.  
                                                 *
                                                 * FIXME(eric) - right now we will just end up falling
                                                 * through to the 'take device offline' case.
                                                 *
                                                 * FIXME(eric) - It is possible that the command completed
                                                 * *after* the error recovery procedure started, and if this
                                                 * is the case, we are worrying about nothing here.
                                                 */

                                                /*
                                                 * Due to the spinlock, we will never get out of this
                                                 * loop without a proper wait (DB)
                                                 */
                                                scsi_sleep(1 * HZ);

                                                goto next_device;
                                        }
                                }
                        }

                        /*
                         * We now know that we are able to perform a reset for the
                         * bus that SCpnt points to.  There are no soft-reset devices
                         * with outstanding timed out commands.
                         */
                        rtn = scsi_try_bus_reset(SCpnt);
                        if (rtn == SUCCESS) {
                                for (SDloop = host->host_queue; SDloop; SDloop = SDloop->next) {
                                        for (SCloop = SDloop->device_queue; SCloop; SCloop = SCloop->next) {
                                                if (SCloop->channel != SCpnt->channel) {
                                                        continue;
                                                }
                                                if (SCloop->state != SCSI_STATE_FAILED
                                                    && SCloop->state != SCSI_STATE_TIMEOUT) {
                                                        continue;
                                                }
                                                rtn = scsi_test_unit_ready(SCloop);

                                                if (rtn == SUCCESS && scsi_unit_is_ready(SCloop)) {
                                                        rtn = scsi_eh_retry_command(SCloop);

                                                        if (rtn == SUCCESS) {
                                                                SCpnt->host->host_failed--;
                                                                scsi_eh_finish_command(&SCdone, SCloop);
                                                        }
                                                }
                                                /*
                                                 * If the bus reset worked, but we are still unable to
                                                 * talk to the device, take it offline.
                                                 * FIXME(eric) - is this really the correct thing to do?
                                                 */
                                                if (rtn != SUCCESS) {
                                                        SCloop->device->online = FALSE;
                                                        SCloop->host->host_failed--;
                                                        scsi_eh_finish_command(&SCdone, SCloop);
                                                }
                                        }
                                }
                        }
                }
        }

        if (host->host_failed == 0) {
                ourrtn = TRUE;
                goto leave;
        }
        /*
         * If we ended up here, we have serious problems.  The only thing left
         * to try is a full host reset - perhaps the firmware on the device
         * crashed, or something like that.
         *
         * It is assumed that a succesful host reset will cause *all* information
         * about the command to be flushed from both the host adapter *and* the
         * device.
         *
         * FIXME(eric) - it isn't clear that devices that implement the soft reset
         * option can ever be cleared except via cycling the power.  The problem is
         * that sending the host reset command will cause the host to forget
         * about the pending command, but the device won't forget.  For now, we
         * skip the host reset option if any of the failed devices are configured
         * to use the soft reset option.
         */
        for (SDpnt = host->host_queue; SDpnt; SDpnt = SDpnt->next) {
              next_device2:
                for (SCpnt = SDpnt->device_queue; SCpnt; SCpnt = SCpnt->next) {
                        if (SCpnt->state != SCSI_STATE_FAILED
                            && SCpnt->state != SCSI_STATE_TIMEOUT) {
                                continue;
                        }
                        if (SDpnt->soft_reset && SCpnt->state == SCSI_STATE_TIMEOUT) {
                                /* 
                                 * If this device uses the soft reset option, and this
                                 * is one of the devices acting up, then our only
                                 * option is to wait a bit, since the command is
                                 * supposedly still running.  
                                 *
                                 * FIXME(eric) - right now we will just end up falling
                                 * through to the 'take device offline' case.
                                 */
                                SCSI_LOG_ERROR_RECOVERY(3,
                                                        printk("scsi_unjam_host: Unable to try hard host reset\n"));

                                /*
                                 * Due to the spinlock, we will never get out of this
                                 * loop without a proper wait. (DB)
                                 */
                                scsi_sleep(1 * HZ);

                                goto next_device2;
                        }
                        SCSI_LOG_ERROR_RECOVERY(3, printk("scsi_unjam_host: Try hard host reset\n"));

                        /*
                         * FIXME(eric) - we need to obtain a valid SCpnt to perform this call.
                         */
                        rtn = scsi_try_host_reset(SCpnt);
                        if (rtn == SUCCESS) {
                                /*
                                 * FIXME(eric) we assume that all commands are flushed from the
                                 * controller.  We should get a DID_RESET for all of the commands
                                 * that were pending.  We should ignore these so that we can
                                 * guarantee that we are in a consistent state.
                                 *
                                 * I believe this to be the case right now, but this needs to be
                                 * tested.
                                 */
                                for (SDloop = host->host_queue; SDloop; SDloop = SDloop->next) {
                                        for (SCloop = SDloop->device_queue; SCloop; SCloop = SCloop->next) {
                                                if (SCloop->state != SCSI_STATE_FAILED
                                                    && SCloop->state != SCSI_STATE_TIMEOUT) {
                                                        continue;
                                                }
                                                rtn = scsi_test_unit_ready(SCloop);

                                                if (rtn == SUCCESS && scsi_unit_is_ready(SCloop)) {
                                                        rtn = scsi_eh_retry_command(SCloop);

                                                        if (rtn == SUCCESS) {
                                                                SCpnt->host->host_failed--;
                                                                scsi_eh_finish_command(&SCdone, SCloop);
                                                        }
                                                }
                                                if (rtn != SUCCESS) {
                                                        SCloop->device->online = FALSE;
                                                        SCloop->host->host_failed--;
                                                        scsi_eh_finish_command(&SCdone, SCloop);
                                                }
                                        }
                                }
                        }
                }
        }

        /*
         * If we solved all of the problems, then let's rev up the engines again.
         */
        if (host->host_failed == 0) {
                ourrtn = TRUE;
                goto leave;
        }
        /*
         * If the HOST RESET failed, then for now we assume that the entire host
         * adapter is too hosed to be of any use.  For our purposes, however, it is
         * easier to simply take the devices offline that correspond to commands
         * that failed.
         */
        SCSI_LOG_ERROR_RECOVERY(1, printk("scsi_unjam_host: Take device offline\n"));

        for (SDpnt = host->host_queue; SDpnt; SDpnt = SDpnt->next) {
                for (SCloop = SDpnt->device_queue; SCloop; SCloop = SCloop->next) {
                        if (SCloop->state == SCSI_STATE_FAILED || SCloop->state == SCSI_STATE_TIMEOUT) {
                                SCloop->device->online = FALSE;

                                /*
                                 * This should pass the failure up to the top level driver, and
                                 * it will have to try and do something intelligent with it.
                                 */
                                SCloop->host->host_failed--;

                                if (SCloop->state == SCSI_STATE_TIMEOUT) {
                                        SCloop->result |= (DRIVER_TIMEOUT << 24);
                                }
                                SCSI_LOG_ERROR_RECOVERY(3, printk("Finishing command for device %d %x\n",
                                    SCloop->device->id, SCloop->result));

                                scsi_eh_finish_command(&SCdone, SCloop);
                        }
                }
        }

        if (host->host_failed != 0) {
                panic("scsi_unjam_host: Miscount of number of failed commands.\n");
        }
        SCSI_LOG_ERROR_RECOVERY(3, printk("scsi_unjam_host: Returning\n"));

        ourrtn = FALSE;

      leave:

        /*
         * We should have a list of commands that we 'finished' during the course of
         * error recovery.  This should be the same as the list of commands that timed out
         * or failed.  We are currently holding these things in a linked list - we didn't
         * put them in the bottom half queue because we wanted to keep things quiet while
         * we were working on recovery, and passing them up to the top level could easily
         * cause the top level to try and queue something else again.
         *
         * Start by marking that the host is no longer in error recovery.
         */
        host->in_recovery = 0;

        /*
         * Take the list of commands, and stick them in the bottom half queue.
         * The current implementation of scsi_done will do this for us - if need
         * be we can create a special version of this function to do the
         * same job for us.
         */
        for (SCpnt = SCdone; SCpnt != NULL; SCpnt = SCdone) {
                SCdone = SCpnt->bh_next;
                SCpnt->bh_next = NULL;
                scsi_done(SCpnt);
        }

        return (ourrtn);
}


/*
 * Function:  scsi_error_handler
 *
 * Purpose:     Handle errors/timeouts of scsi commands, try and clean up
 *              and unjam the bus, and restart things.
 *
 * Arguments:   host    - host for which we are running.
 *
 * Returns:     Never returns.
 *
 * Notes:       This is always run in the context of a kernel thread.  The
 *              idea is that we start this thing up when the kernel starts
 *              up (one per host that we detect), and it immediately goes to
 *              sleep and waits for some event (i.e. failure).  When this
 *              takes place, we have the job of trying to unjam the bus
 *              and restarting things.
 *
 */
void scsi_error_handler(void *data)
{
        struct Scsi_Host *host = (struct Scsi_Host *) data;
        int rtn;
        DECLARE_MUTEX_LOCKED(sem);
        unsigned long flags;
        struct fs_struct *fs;

        lock_kernel();

        /*
         * If we were started as result of loading a module, close all of the
         * user space pages.  We don't need them, and if we didn't close them
         * they would be locked into memory.
         */
        exit_mm(current);

        current->session = 1;
        current->pgrp = 1;

        /* Become as one with the init task */

        exit_fs(current);       /* current->fs->count--; */
        fs = init_task.fs;
        current->fs = fs;
        atomic_inc(&fs->count);

        siginitsetinv(&current->blocked, SHUTDOWN_SIGS);


        /*
         * Set the name of this process.
         */
        sprintf(current->comm, "scsi_eh_%d", host->host_no);

        host->eh_wait = &sem;
        host->ehandler = current;

        unlock_kernel();

        /*
         * Wake up the thread that created us.
         */
        SCSI_LOG_ERROR_RECOVERY(3, printk("Wake up parent %d\n", host->eh_notify->count.counter));

        up(host->eh_notify);

        while (1) {
                /*
                 * If we get a signal, it means we are supposed to go
                 * away and die.  This typically happens if the user is
                 * trying to unload a module.
                 */
                SCSI_LOG_ERROR_RECOVERY(1, printk("Error handler sleeping\n"));
                down_interruptible(&sem);

                if (signal_pending(current))
                        break;

                SCSI_LOG_ERROR_RECOVERY(1, printk("Error handler waking up\n"));

                spin_lock_irqsave(&io_request_lock, flags);
                host->eh_active = 1;

                /*
                 * We have a host that is failing for some reason.  Figure out
                 * what we need to do to get it up and online again (if we can).
                 * If we fail, we end up taking the thing offline.
                 */
                if (host->hostt->eh_strategy_handler != NULL) {
                        rtn = host->hostt->eh_strategy_handler(host);
                } else {
                        rtn = scsi_unjam_host(host);
                }

                host->eh_active = 0;

                /*
                 * Note - if the above fails completely, the action is to take
                 * individual devices offline and flush the queue of any
                 * outstanding requests that may have been pending.  When we
                 * restart, we restart any I/O to any other devices on the bus
                 * which are still online.
                 */
                scsi_restart_operations(host);

                /* The spinlock is really needed up to this point. (DB) */
                spin_unlock_irqrestore(&io_request_lock, flags);
        }

        SCSI_LOG_ERROR_RECOVERY(1, printk("Error handler exiting\n"));

        /*
         * Make sure that nobody tries to wake us up again.
         */
        host->eh_wait = NULL;

        /*
         * Knock this down too.  From this point on, the host is flying
         * without a pilot.  If this is because the module is being unloaded,
         * that's fine.  If the user sent a signal to this thing, we are
         * potentially in real danger.
         */
        host->in_recovery = 0;
        host->eh_active = 0;
        host->ehandler = NULL;

        /*
         * If anyone is waiting for us to exit (i.e. someone trying to unload
         * a driver), then wake up that process to let them know we are on
         * the way out the door.  This may be overkill - I *think* that we
         * could probably just unload the driver and send the signal, and when
         * the error handling thread wakes up that it would just exit without
         * needing to touch any memory associated with the driver itself.
         */
        if (host->eh_notify != NULL)
                up(host->eh_notify);
}

/*
 * Overrides for Emacs so that we follow Linus's tabbing style.
 * Emacs will notice this stuff at the end of the file and automatically
 * adjust the settings for this buffer only.  This must remain at the end
 * of the file.
 * ---------------------------------------------------------------------------
 * Local variables:
 * c-indent-level: 4
 * c-brace-imaginary-offset: 0
 * c-brace-offset: -4
 * c-argdecl-indent: 4
 * c-label-offset: -4
 * c-continued-statement-offset: 4
 * c-continued-brace-offset: 0
 * indent-tabs-mode: nil
 * tab-width: 8
 * End:
 */