py/dnsserver: add a missing exception variable

[Samba.git] / lib / tevent / tevent_threads.c

/*
   tevent event library.

   Copyright (C) Jeremy Allison 2015

     ** NOTE! The following LGPL license applies to the tevent
     ** library. This does NOT imply that all of Samba is released
     ** under the LGPL

   This library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
   License as published by the Free Software Foundation; either
   version 3 of the License, or (at your option) any later version.

   This library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with this library; if not, see <http://www.gnu.org/licenses/>.
*/

#include "replace.h"
#include "system/filesys.h"
#include "talloc.h"
#include "tevent.h"
#include "tevent_internal.h"
#include "tevent_util.h"

#ifdef HAVE_PTHREAD
#include "system/threads.h"

struct tevent_immediate_list {
        struct tevent_immediate_list *next, *prev;
        tevent_immediate_handler_t handler;
        struct tevent_immediate *im;
        void *private_ptr;
};

struct tevent_thread_proxy {
        pthread_mutex_t mutex;
        struct tevent_context *dest_ev_ctx;
        int read_fd;
        int write_fd;
        struct tevent_fd *pipe_read_fde;
        /* Pending events list. */
        struct tevent_immediate_list *im_list;
        /* Completed events list. */
        struct tevent_immediate_list *tofree_im_list;
        struct tevent_immediate *free_im;
};

static void free_im_list(struct tevent_immediate_list **pp_list_head)
{
        struct tevent_immediate_list *im_entry = NULL;
        struct tevent_immediate_list *im_next = NULL;

        for (im_entry = *pp_list_head; im_entry; im_entry = im_next) {
                im_next = im_entry->next;
                DLIST_REMOVE(*pp_list_head, im_entry);
                TALLOC_FREE(im_entry);
        }
}

static void free_list_handler(struct tevent_context *ev,
                                struct tevent_immediate *im,
                                void *private_ptr)
{
        struct tevent_thread_proxy *tp =
                talloc_get_type_abort(private_ptr, struct tevent_thread_proxy);
        int ret;

        ret = pthread_mutex_lock(&tp->mutex);
        if (ret != 0) {
                abort();
                /* Notreached. */
                return;
        }

        free_im_list(&tp->tofree_im_list);

        ret = pthread_mutex_unlock(&tp->mutex);
        if (ret != 0) {
                abort();
                /* Notreached. */
                return;
        }
}

static void schedule_immediate_functions(struct tevent_thread_proxy *tp)
{
        struct tevent_immediate_list *im_entry = NULL;
        struct tevent_immediate_list *im_next = NULL;

        for (im_entry = tp->im_list; im_entry; im_entry = im_next) {
                im_next = im_entry->next;
                DLIST_REMOVE(tp->im_list, im_entry);

                tevent_schedule_immediate(im_entry->im,
                                        tp->dest_ev_ctx,
                                        im_entry->handler,
                                        im_entry->private_ptr);

                /* Move from pending list to free list. */
                DLIST_ADD(tp->tofree_im_list, im_entry);
        }
        if (tp->tofree_im_list != NULL) {
                /*
                 * Once the current immediate events
                 * are processed, we need to reschedule
                 * ourselves to free them. This works
                 * as tevent_schedule_immediate()
                 * always adds events to the *END* of
                 * the immediate events list.
                 */
                tevent_schedule_immediate(tp->free_im,
                                        tp->dest_ev_ctx,
                                        free_list_handler,
                                        tp);
        }
}

static void pipe_read_handler(struct tevent_context *ev,
                                struct tevent_fd *fde,
                                uint16_t flags,
                                void *private_ptr)
{
        struct tevent_thread_proxy *tp =
                talloc_get_type_abort(private_ptr, struct tevent_thread_proxy);
        ssize_t len = 64;
        int ret;

        ret = pthread_mutex_lock(&tp->mutex);
        if (ret != 0) {
                abort();
                /* Notreached. */
                return;
        }

        /*
         * Clear out all data in the pipe. We
         * don't really care if this returns -1.
         */
        while (len == 64) {
                char buf[64];
                len = read(tp->read_fd, buf, 64);
        };

        schedule_immediate_functions(tp);

        ret = pthread_mutex_unlock(&tp->mutex);
        if (ret != 0) {
                abort();
                /* Notreached. */
                return;
        }
}

static int tevent_thread_proxy_destructor(struct tevent_thread_proxy *tp)
{
        int ret;

        ret = pthread_mutex_lock(&tp->mutex);
        if (ret != 0) {
                abort();
                /* Notreached. */
                return 0;
        }

        TALLOC_FREE(tp->pipe_read_fde);

        if (tp->read_fd != -1) {
                (void)close(tp->read_fd);
                tp->read_fd = -1;
        }
        if (tp->write_fd != -1) {
                (void)close(tp->write_fd);
                tp->write_fd = -1;
        }

        /* Hmmm. It's probably an error if we get here with
           any non-NULL immediate entries.. */

        free_im_list(&tp->im_list);
        free_im_list(&tp->tofree_im_list);

        TALLOC_FREE(tp->free_im);

        ret = pthread_mutex_unlock(&tp->mutex);
        if (ret != 0) {
                abort();
                /* Notreached. */
                return 0;
        }

        ret = pthread_mutex_destroy(&tp->mutex);
        if (ret != 0) {
                abort();
                /* Notreached. */
                return 0;
        }

        return 0;
}

/*
 * Create a struct that can be passed to other threads
 * to allow them to signal the struct tevent_context *
 * passed in.
 */

struct tevent_thread_proxy *tevent_thread_proxy_create(
                struct tevent_context *dest_ev_ctx)
{
        int ret;
        int pipefds[2];
        struct tevent_thread_proxy *tp;

        if (dest_ev_ctx->wrapper.glue != NULL) {
                /*
                 * stacking of wrappers is not supported
                 */
                tevent_debug(dest_ev_ctx->wrapper.glue->main_ev,
                             TEVENT_DEBUG_FATAL,
                             "%s() not allowed on a wrapper context\n",
                             __func__);
                errno = EINVAL;
                return NULL;
        }

        tp = talloc_zero(dest_ev_ctx, struct tevent_thread_proxy);
        if (tp == NULL) {
                return NULL;
        }

        ret = pthread_mutex_init(&tp->mutex, NULL);
        if (ret != 0) {
                goto fail;
        }

        tp->dest_ev_ctx = dest_ev_ctx;
        tp->read_fd = -1;
        tp->write_fd = -1;

        talloc_set_destructor(tp, tevent_thread_proxy_destructor);

        ret = pipe(pipefds);
        if (ret == -1) {
                goto fail;
        }

        tp->read_fd = pipefds[0];
        tp->write_fd = pipefds[1];

        ret = ev_set_blocking(pipefds[0], false);
        if (ret != 0) {
                goto fail;
        }
        ret = ev_set_blocking(pipefds[1], false);
        if (ret != 0) {
                goto fail;
        }
        if (!ev_set_close_on_exec(pipefds[0])) {
                goto fail;
        }
        if (!ev_set_close_on_exec(pipefds[1])) {
                goto fail;
        }

        tp->pipe_read_fde = tevent_add_fd(dest_ev_ctx,
                                tp,
                                tp->read_fd,
                                TEVENT_FD_READ,
                                pipe_read_handler,
                                tp);
        if (tp->pipe_read_fde == NULL) {
                goto fail;
        }

        /*
         * Create an immediate event to free
         * completed lists.
         */
        tp->free_im = tevent_create_immediate(tp);
        if (tp->free_im == NULL) {
                goto fail;
        }

        return tp;

  fail:

        TALLOC_FREE(tp);
        return NULL;
}

/*
 * This function schedules an immediate event to be called with argument
 * *pp_private in the thread context of dest_ev_ctx. Caller doesn't
 * wait for activation to take place, this is simply fire-and-forget.
 *
 * pp_im must be a pointer to an immediate event talloced on
 * a context owned by the calling thread, or the NULL context.
 * Ownership of *pp_im will be transfered to the tevent library.
 *
 * pp_private can be null, or contents of *pp_private must be
 * talloc'ed memory on a context owned by the calling thread
 * or the NULL context. If non-null, ownership of *pp_private will
 * be transfered to the tevent library.
 *
 * If you want to return a message, have the destination use the
 * same function call to send back to the caller.
 */


void tevent_thread_proxy_schedule(struct tevent_thread_proxy *tp,
                                  struct tevent_immediate **pp_im,
                                  tevent_immediate_handler_t handler,
                                  void *pp_private_data)
{
        struct tevent_immediate_list *im_entry;
        int ret;
        char c;
        ssize_t written;

        ret = pthread_mutex_lock(&tp->mutex);
        if (ret != 0) {
                abort();
                /* Notreached. */
                return;
        }

        if (tp->write_fd == -1) {
                /* In the process of being destroyed. Ignore. */
                goto end;
        }

        /* Create a new immediate_list entry. MUST BE ON THE NULL CONTEXT */
        im_entry = talloc_zero(NULL, struct tevent_immediate_list);
        if (im_entry == NULL) {
                goto end;
        }

        im_entry->handler = handler;
        im_entry->im = talloc_move(im_entry, pp_im);

        if (pp_private_data != NULL) {
                void **pptr = (void **)pp_private_data;
                im_entry->private_ptr = talloc_move(im_entry, pptr);
        }

        DLIST_ADD(tp->im_list, im_entry);

        /* And notify the dest_ev_ctx to wake up. */
        c = '\0';
        do {
                written = write(tp->write_fd, &c, 1);
        } while (written == -1 && errno == EINTR);

  end:

        ret = pthread_mutex_unlock(&tp->mutex);
        if (ret != 0) {
                abort();
                /* Notreached. */
        }
}
#else
/* !HAVE_PTHREAD */
struct tevent_thread_proxy *tevent_thread_proxy_create(
                struct tevent_context *dest_ev_ctx)
{
        errno = ENOSYS;
        return NULL;
}

void tevent_thread_proxy_schedule(struct tevent_thread_proxy *tp,
                                  struct tevent_immediate **pp_im,
                                  tevent_immediate_handler_t handler,
                                  void *pp_private_data)
{
        ;
}
#endif

static int tevent_threaded_context_destructor(
        struct tevent_threaded_context *tctx)
{
        struct tevent_context *main_ev = tevent_wrapper_main_ev(tctx->event_ctx);
        int ret;

        if (main_ev != NULL) {
                DLIST_REMOVE(main_ev->threaded_contexts, tctx);
        }

        /*
         * We have to coordinate with _tevent_threaded_schedule_immediate's
         * unlock of the event_ctx_mutex. We're in the main thread here,
         * and we can be scheduled before the helper thread finalizes its
         * call _tevent_threaded_schedule_immediate. This means we would
         * pthreadpool_destroy a locked mutex, which is illegal.
         */
        ret = pthread_mutex_lock(&tctx->event_ctx_mutex);
        if (ret != 0) {
                abort();
        }

        ret = pthread_mutex_unlock(&tctx->event_ctx_mutex);
        if (ret != 0) {
                abort();
        }

        ret = pthread_mutex_destroy(&tctx->event_ctx_mutex);
        if (ret != 0) {
                abort();
        }

        return 0;
}

struct tevent_threaded_context *tevent_threaded_context_create(
        TALLOC_CTX *mem_ctx, struct tevent_context *ev)
{
#ifdef HAVE_PTHREAD
        struct tevent_context *main_ev = tevent_wrapper_main_ev(ev);
        struct tevent_threaded_context *tctx;
        int ret;

        ret = tevent_common_wakeup_init(main_ev);
        if (ret != 0) {
                errno = ret;
                return NULL;
        }

        tctx = talloc(mem_ctx, struct tevent_threaded_context);
        if (tctx == NULL) {
                return NULL;
        }
        tctx->event_ctx = ev;

        ret = pthread_mutex_init(&tctx->event_ctx_mutex, NULL);
        if (ret != 0) {
                TALLOC_FREE(tctx);
                return NULL;
        }

        DLIST_ADD(main_ev->threaded_contexts, tctx);
        talloc_set_destructor(tctx, tevent_threaded_context_destructor);

        return tctx;
#else
        errno = ENOSYS;
        return NULL;
#endif
}

static int tevent_threaded_schedule_immediate_destructor(struct tevent_immediate *im)
{
        if (im->event_ctx != NULL) {
                abort();
        }
        return 0;
}

void _tevent_threaded_schedule_immediate(struct tevent_threaded_context *tctx,
                                         struct tevent_immediate *im,
                                         tevent_immediate_handler_t handler,
                                         void *private_data,
                                         const char *handler_name,
                                         const char *location)
{
#ifdef HAVE_PTHREAD
        const char *create_location = im->create_location;
        struct tevent_context *main_ev = NULL;
        struct tevent_wrapper_glue *glue = NULL;
        int ret, wakeup_fd;

        ret = pthread_mutex_lock(&tctx->event_ctx_mutex);
        if (ret != 0) {
                abort();
        }

        if (tctx->event_ctx == NULL) {
                /*
                 * Our event context is already gone.
                 */
                ret = pthread_mutex_unlock(&tctx->event_ctx_mutex);
                if (ret != 0) {
                        abort();
                }
                return;
        }

        glue = tctx->event_ctx->wrapper.glue;

        if ((im->event_ctx != NULL) || (handler == NULL)) {
                abort();
        }
        if (im->destroyed) {
                abort();
        }
        if (im->busy) {
                abort();
        }

        main_ev = tevent_wrapper_main_ev(tctx->event_ctx);

        *im = (struct tevent_immediate) {
                .event_ctx              = tctx->event_ctx,
                .wrapper                = glue,
                .handler                = handler,
                .private_data           = private_data,
                .handler_name           = handler_name,
                .create_location        = create_location,
                .schedule_location      = location,
        };

        /*
         * Make sure the event won't be destroyed while
         * it's part of the ev->scheduled_immediates list.
         * _tevent_schedule_immediate() will reset the destructor
         * in tevent_common_threaded_activate_immediate().
         */
        talloc_set_destructor(im, tevent_threaded_schedule_immediate_destructor);

        ret = pthread_mutex_lock(&main_ev->scheduled_mutex);
        if (ret != 0) {
                abort();
        }

        DLIST_ADD_END(main_ev->scheduled_immediates, im);
        wakeup_fd = main_ev->wakeup_fd;

        ret = pthread_mutex_unlock(&main_ev->scheduled_mutex);
        if (ret != 0) {
                abort();
        }

        ret = pthread_mutex_unlock(&tctx->event_ctx_mutex);
        if (ret != 0) {
                abort();
        }

        /*
         * We might want to wake up the main thread under the lock. We
         * had a slightly similar situation in pthreadpool, changed
         * with 1c4284c7395f23. This is not exactly the same, as the
         * wakeup is only a last-resort thing in case the main thread
         * is sleeping. Doing the wakeup under the lock can easily
         * lead to a contended mutex, which is much more expensive
         * than a noncontended one. So I'd opt for the lower footprint
         * initially. Maybe we have to change that later.
         */
        tevent_common_wakeup_fd(wakeup_fd);
#else
        /*
         * tevent_threaded_context_create() returned NULL with ENOSYS...
         */
        abort();
#endif
}

void tevent_common_threaded_activate_immediate(struct tevent_context *ev)
{
#ifdef HAVE_PTHREAD
        int ret;
        ret = pthread_mutex_lock(&ev->scheduled_mutex);
        if (ret != 0) {
                abort();
        }

        while (ev->scheduled_immediates != NULL) {
                struct tevent_immediate *im = ev->scheduled_immediates;
                struct tevent_immediate copy = *im;

                DLIST_REMOVE(ev->scheduled_immediates, im);

                tevent_debug(ev, TEVENT_DEBUG_TRACE,
                             "Schedule immediate event \"%s\": %p from thread into main\n",
                             im->handler_name, im);
                im->handler_name = NULL;
                _tevent_schedule_immediate(im,
                                           ev,
                                           copy.handler,
                                           copy.private_data,
                                           copy.handler_name,
                                           copy.schedule_location);
        }

        ret = pthread_mutex_unlock(&ev->scheduled_mutex);
        if (ret != 0) {
                abort();
        }
#else
        /*
         * tevent_threaded_context_create() returned NULL with ENOSYS...
         */
        abort();
#endif
}