sys/kern/lwkt_serialize.c

   1 /*
   2  * Copyright (c) 2005 The DragonFly Project.  All rights reserved.
   3  *
   4  * This code is derived from software contributed to The DragonFly Project
   5  * by Matthew Dillon <dillon@backplane.com>
   6  *
   7  * Redistribution and use in source and binary forms, with or without
   8  * modification, are permitted provided that the following conditions
   9  * are met:
  10  *
  11  * 1. Redistributions of source code must retain the above copyright
  12  *    notice, this list of conditions and the following disclaimer.
  13  * 2. Redistributions in binary form must reproduce the above copyright
  14  *    notice, this list of conditions and the following disclaimer in
  15  *    the documentation and/or other materials provided with the
  16  *    distribution.
  17  * 3. Neither the name of The DragonFly Project nor the names of its
  18  *    contributors may be used to endorse or promote products derived
  19  *    from this software without specific, prior written permission.
  20  *
  21  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  22  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  23  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
  24  * FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE
  25  * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
  26  * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING,
  27  * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  28  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
  29  * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
  30  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
  31  * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  32  * SUCH DAMAGE.
  33  *
  34  * $DragonFly: src/sys/kern/lwkt_serialize.c,v 1.9 2005/12/01 18:34:09 dillon Exp $
  35  */
  36 /*
  37  * This API provides a fast locked-bus-cycle-based serializer.  It's
  38  * basically a low level NON-RECURSIVE exclusive lock that can be held across
  39  * a blocking condition.  It is NOT a mutex.
  40  *
  41  * This serializer is primarily designed for low level situations and
  42  * interrupt/device interaction.  There are two primary facilities.  First,
  43  * the serializer facility itself.  Second, an integrated interrupt handler
  44  * disablement facility.
  45  */
  46
  47 #include <sys/param.h>
  48 #include <sys/systm.h>
  49 #include <sys/kernel.h>
  50 #include <sys/proc.h>
  51 #include <sys/rtprio.h>
  52 #include <sys/queue.h>
  53 #include <sys/thread2.h>
  54 #include <sys/serialize.h>
  55 #include <sys/sysctl.h>
  56 #include <sys/kthread.h>
  57 #include <machine/cpu.h>
  58 #include <sys/lock.h>
  59 #include <sys/caps.h>
  60
  61 static void lwkt_serialize_sleep(void *info);
  62 static void lwkt_serialize_wakeup(void *info);
  63
  64 void
  65 lwkt_serialize_init(lwkt_serialize_t s)
  66 {
  67     atomic_intr_init(&s->interlock);
  68 #ifdef INVARIANTS
  69     s->last_td = (void *)-4;
  70 #endif
  71 }
  72
  73 void
  74 lwkt_serialize_enter(lwkt_serialize_t s)
  75 {
  76 #ifdef INVARIANTS
  77     KKASSERT(s->last_td != curthread);
  78 #endif
  79     atomic_intr_cond_enter(&s->interlock, lwkt_serialize_sleep, s);
  80 #ifdef INVARIANTS
  81     s->last_td = curthread;
  82 #endif
  83 }
  84
  85 /*
  86  * Returns non-zero on success
  87  */
  88 int
  89 lwkt_serialize_try(lwkt_serialize_t s)
  90 {
  91     int error;
  92
  93 #ifdef INVARIANTS
  94     KKASSERT(s->last_td != curthread);
  95 #endif
  96     if ((error = atomic_intr_cond_try(&s->interlock)) == 0) {
  97 #ifdef INVARIANTS
  98         s->last_td = curthread;
  99 #endif
 100         return(1);
 101     }
 102     return (0);
 103 }
 104
 105 void
 106 lwkt_serialize_exit(lwkt_serialize_t s)
 107 {
 108 #ifdef INVARIANTS
 109     KKASSERT(s->last_td == curthread);
 110     s->last_td = (void *)-2;
 111 #endif
 112     atomic_intr_cond_exit(&s->interlock, lwkt_serialize_wakeup, s);
 113 }
 114
 115 /*
 116  * Interrupt handler disablement support, used by drivers.  Non-stackable
 117  * (uses bit 30).
 118  */
 119 void
 120 lwkt_serialize_handler_disable(lwkt_serialize_t s)
 121 {
 122     atomic_intr_handler_disable(&s->interlock);
 123 }
 124
 125 void
 126 lwkt_serialize_handler_enable(lwkt_serialize_t s)
 127 {
 128     atomic_intr_handler_enable(&s->interlock);
 129 }
 130
 131 void
 132 lwkt_serialize_handler_call(lwkt_serialize_t s, void (*func)(void *, void *),
 133                             void *arg, void *frame)
 134 {
 135     /*
 136      * note: a return value of 0 indicates that the interrupt handler is
 137      * enabled.
 138      */
 139     if (atomic_intr_handler_is_enabled(&s->interlock) == 0) {
 140         atomic_intr_cond_enter(&s->interlock, lwkt_serialize_sleep, s);
 141 #ifdef INVARIANTS
 142         s->last_td = curthread;
 143 #endif
 144         if (atomic_intr_handler_is_enabled(&s->interlock) == 0)
 145             func(arg, frame);
 146 #ifdef INVARIANTS
 147         KKASSERT(s->last_td == curthread);
 148         s->last_td = (void *)-2;
 149 #endif
 150         atomic_intr_cond_exit(&s->interlock, lwkt_serialize_wakeup, s);
 151     }
 152 }
 153
 154 /*
 155  * Similar to handler_call but does not block.  Returns 0 on success,
 156  * and 1 on failure.
 157  */
 158 int
 159 lwkt_serialize_handler_try(lwkt_serialize_t s, void (*func)(void *, void *),
 160                            void *arg, void *frame)
 161 {
 162     /*
 163      * note: a return value of 0 indicates that the interrupt handler is
 164      * enabled.
 165      */
 166     if (atomic_intr_handler_is_enabled(&s->interlock) == 0) {
 167         if (atomic_intr_cond_try(&s->interlock) == 0) {
 168 #ifdef INVARIANTS
 169             s->last_td = curthread;
 170 #endif
 171             func(arg, frame);
 172 #ifdef INVARIANTS
 173             KKASSERT(s->last_td == curthread);
 174             s->last_td = (void *)-2;
 175 #endif
 176             atomic_intr_cond_exit(&s->interlock, lwkt_serialize_wakeup, s);
 177             return(0);
 178         }
 179     }
 180     return(1);
 181 }
 182
 183
 184 /*
 185  * Helper functions
 186  *
 187  * It is possible to race an interrupt which acquires and releases the
 188  * bit, then calls wakeup before we actually go to sleep, so we
 189  * need to check that the interlock is still acquired from within
 190  * a critical section prior to sleeping.
 191  */
 192 static void
 193 lwkt_serialize_sleep(void *info)
 194 {
 195     lwkt_serialize_t s = info;
 196     crit_enter();
 197     tsleep_interlock(s);
 198     if (atomic_intr_cond_test(&s->interlock) != 0)
 199             tsleep(s, 0, "slize", 0);
 200     crit_exit();
 201 }
 202
 203 static void
 204 lwkt_serialize_wakeup(void *info)
 205 {
 206     wakeup(info);
 207 }
 208