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 /*
  35  * This API provides a fast locked-bus-cycle-based serializer.  It's
  36  * basically a low level NON-RECURSIVE exclusive lock that can be held across
  37  * a blocking condition.  It is NOT a mutex.
  38  *
  39  * This serializer is primarily designed for low level situations and
  40  * interrupt/device interaction.  There are two primary facilities.  First,
  41  * the serializer facility itself.  Second, an integrated interrupt handler
  42  * disablement facility.
  43  */
  44
  45 #include <sys/param.h>
  46 #include <sys/systm.h>
  47 #include <sys/kernel.h>
  48 #include <sys/proc.h>
  49 #include <sys/rtprio.h>
  50 #include <sys/queue.h>
  51 #include <sys/serialize.h>
  52 #include <sys/sysctl.h>
  53 #include <sys/ktr.h>
  54 #include <sys/kthread.h>
  55 #include <machine/cpu.h>
  56 #include <machine/cpufunc.h>
  57 #include <machine/specialreg.h>
  58 #include <machine/clock.h>
  59 #include <sys/lock.h>
  60
  61 #ifndef SLZ_ADAPTIVE_SPINMAX
  62 #define SLZ_ADAPTIVE_SPINMAX    4096
  63 #endif
  64
  65 #define SLZ_KTR_STRING          "slz=%p"
  66 #define SLZ_KTR_ARGS            lwkt_serialize_t slz
  67
  68 #ifndef KTR_SERIALIZER
  69 #define KTR_SERIALIZER          KTR_ALL
  70 #endif
  71
  72 KTR_INFO_MASTER(slz);
  73 KTR_INFO(KTR_SERIALIZER, slz, enter_beg, 0, SLZ_KTR_STRING, SLZ_KTR_ARGS);
  74 KTR_INFO(KTR_SERIALIZER, slz, sleep_beg, 1, SLZ_KTR_STRING, SLZ_KTR_ARGS);
  75 KTR_INFO(KTR_SERIALIZER, slz, sleep_end, 2, SLZ_KTR_STRING, SLZ_KTR_ARGS);
  76 KTR_INFO(KTR_SERIALIZER, slz, exit_end, 3, SLZ_KTR_STRING, SLZ_KTR_ARGS);
  77 KTR_INFO(KTR_SERIALIZER, slz, wakeup_beg, 4, SLZ_KTR_STRING, SLZ_KTR_ARGS);
  78 KTR_INFO(KTR_SERIALIZER, slz, wakeup_end, 5, SLZ_KTR_STRING, SLZ_KTR_ARGS);
  79 KTR_INFO(KTR_SERIALIZER, slz, try, 6, SLZ_KTR_STRING, SLZ_KTR_ARGS);
  80 KTR_INFO(KTR_SERIALIZER, slz, tryfail, 7, SLZ_KTR_STRING, SLZ_KTR_ARGS);
  81 KTR_INFO(KTR_SERIALIZER, slz, tryok, 8, SLZ_KTR_STRING, SLZ_KTR_ARGS);
  82 KTR_INFO(KTR_SERIALIZER, slz, enter_end, 9, SLZ_KTR_STRING, SLZ_KTR_ARGS);
  83 KTR_INFO(KTR_SERIALIZER, slz, exit_beg, 10, SLZ_KTR_STRING, SLZ_KTR_ARGS);
  84 KTR_INFO(KTR_SERIALIZER, slz, adapt_beg, 11, SLZ_KTR_STRING, SLZ_KTR_ARGS);
  85 KTR_INFO(KTR_SERIALIZER, slz, adapt_end, 12, SLZ_KTR_STRING, SLZ_KTR_ARGS);
  86 KTR_INFO(KTR_SERIALIZER, slz, adapt_spinend, 13, "slz=%p try=%d",
  87     lwkt_serialize_t slz, int try);
  88 KTR_INFO(KTR_SERIALIZER, slz, adapt_sleepb, 14, SLZ_KTR_STRING, SLZ_KTR_ARGS);
  89 KTR_INFO(KTR_SERIALIZER, slz, adapt_sleepe, 15, SLZ_KTR_STRING, SLZ_KTR_ARGS);
  90
  91 #define logslz(name, slz)               KTR_LOG(slz_ ## name, slz)
  92 #define logslz_spinend(slz, try)        KTR_LOG(slz_adapt_spinend, slz, try)
  93
  94 static void lwkt_serialize_sleep(void *info);
  95 static void lwkt_serialize_wakeup(void *info);
  96
  97 void
  98 lwkt_serialize_init(lwkt_serialize_t s)
  99 {
 100     atomic_intr_init(&s->interlock);
 101     s->last_td = (void *)-4;
 102 }
 103
 104 void
 105 lwkt_serialize_enter(lwkt_serialize_t s)
 106 {
 107     ASSERT_NOT_SERIALIZED(s);
 108
 109     logslz(enter_beg, s);
 110     atomic_intr_cond_enter(&s->interlock, lwkt_serialize_sleep, s);
 111     logslz(enter_end, s);
 112     s->last_td = curthread;
 113 }
 114
 115 /*
 116  * Returns non-zero on success
 117  */
 118 int
 119 lwkt_serialize_try(lwkt_serialize_t s)
 120 {
 121     int error;
 122
 123     ASSERT_NOT_SERIALIZED(s);
 124
 125     logslz(try, s);
 126     if ((error = atomic_intr_cond_try(&s->interlock)) == 0) {
 127         s->last_td = curthread;
 128         logslz(tryok, s);
 129         return(1);
 130     }
 131     logslz(tryfail, s);
 132     return (0);
 133 }
 134
 135 void
 136 lwkt_serialize_exit(lwkt_serialize_t s)
 137 {
 138     ASSERT_SERIALIZED(s);
 139     s->last_td = (void *)-2;
 140     logslz(exit_beg, s);
 141     atomic_intr_cond_exit(&s->interlock, lwkt_serialize_wakeup, s);
 142     logslz(exit_end, s);
 143 }
 144
 145 /*
 146  * Interrupt handler disablement support, used by drivers.  Non-stackable
 147  * (uses bit 30).
 148  */
 149 void
 150 lwkt_serialize_handler_disable(lwkt_serialize_t s)
 151 {
 152     atomic_intr_handler_disable(&s->interlock);
 153 }
 154
 155 void
 156 lwkt_serialize_handler_enable(lwkt_serialize_t s)
 157 {
 158     atomic_intr_handler_enable(&s->interlock);
 159 }
 160
 161 void
 162 lwkt_serialize_handler_call(lwkt_serialize_t s, void (*func)(void *, void *),
 163                             void *arg, void *frame)
 164 {
 165     /*
 166      * note: a return value of 0 indicates that the interrupt handler is
 167      * enabled.
 168      */
 169     if (atomic_intr_handler_is_enabled(&s->interlock) == 0) {
 170         logslz(enter_beg, s);
 171         atomic_intr_cond_enter(&s->interlock, lwkt_serialize_sleep, s);
 172         logslz(enter_end, s);
 173         s->last_td = curthread;
 174         if (atomic_intr_handler_is_enabled(&s->interlock) == 0)
 175             func(arg, frame);
 176
 177         ASSERT_SERIALIZED(s);
 178         s->last_td = (void *)-2;
 179         logslz(exit_beg, s);
 180         atomic_intr_cond_exit(&s->interlock, lwkt_serialize_wakeup, s);
 181         logslz(exit_end, s);
 182     }
 183 }
 184
 185 /*
 186  * Similar to handler_call but does not block.  Returns 0 on success,
 187  * and 1 on failure.
 188  */
 189 int
 190 lwkt_serialize_handler_try(lwkt_serialize_t s, void (*func)(void *, void *),
 191                            void *arg, void *frame)
 192 {
 193     /*
 194      * note: a return value of 0 indicates that the interrupt handler is
 195      * enabled.
 196      */
 197     if (atomic_intr_handler_is_enabled(&s->interlock) == 0) {
 198         logslz(try, s);
 199         if (atomic_intr_cond_try(&s->interlock) == 0) {
 200             s->last_td = curthread;
 201             logslz(tryok, s);
 202
 203             func(arg, frame);
 204
 205             ASSERT_SERIALIZED(s);
 206             s->last_td = (void *)-2;
 207             logslz(exit_beg, s);
 208             atomic_intr_cond_exit(&s->interlock, lwkt_serialize_wakeup, s);
 209             logslz(exit_end, s);
 210             return(0);
 211         }
 212     }
 213     logslz(tryfail, s);
 214     return(1);
 215 }
 216
 217
 218 /*
 219  * Helper functions
 220  *
 221  * It is possible to race an interrupt which acquires and releases the
 222  * bit, then calls wakeup before we actually go to sleep, so we
 223  * need to check that the interlock is still acquired from within
 224  * a critical section prior to sleeping.
 225  */
 226 static void
 227 lwkt_serialize_sleep(void *info)
 228 {
 229     lwkt_serialize_t s = info;
 230
 231     tsleep_interlock(s, 0);
 232     if (atomic_intr_cond_test(&s->interlock) != 0) {
 233         logslz(sleep_beg, s);
 234         tsleep(s, PINTERLOCKED, "slize", 0);
 235         logslz(sleep_end, s);
 236     }
 237 }
 238
 239 void
 240 lwkt_serialize_adaptive_enter(lwkt_serialize_t s)
 241 {
 242     int try;
 243
 244     ASSERT_NOT_SERIALIZED(s);
 245     logslz(adapt_beg, s);
 246
 247     if (atomic_intr_cond_try(&s->interlock) == 0) {
 248         s->last_td = curthread;
 249         logslz(adapt_end, s);
 250         return;
 251     }
 252
 253 restart:
 254     /*
 255      * Spinning a little bit, before going to sleep
 256      *
 257      * See the comment before kern/kern_spinlock.c
 258      * _spin_lock_contested() about why atomic_intr_cond_test()
 259      * is called first.  atomic_intr_cond_test() contains
 260      * _no_ MPLOCKED intruction.
 261      */
 262     for (try = SLZ_ADAPTIVE_SPINMAX; try; --try) {
 263         if (atomic_intr_cond_test(&s->interlock) == 0 &&
 264             atomic_intr_cond_try(&s->interlock) == 0) {
 265             s->last_td = curthread;
 266             logslz_spinend(s, try);
 267             return;
 268         }
 269     }
 270
 271     atomic_intr_cond_inc(&s->interlock);
 272
 273     tsleep_interlock(s, 0);
 274     if (atomic_intr_cond_try(&s->interlock) == 0) {
 275         atomic_intr_cond_dec(&s->interlock);
 276         s->last_td = curthread;
 277         logslz_spinend(s, 0);
 278         return;
 279     } else {
 280         logslz(adapt_sleepb, s);
 281         tsleep(s, PINTERLOCKED, "aslize", 0);
 282         logslz(adapt_sleepe, s);
 283
 284         atomic_intr_cond_dec(&s->interlock);
 285         goto restart;
 286     }
 287 }
 288
 289 static void
 290 lwkt_serialize_wakeup(void *info)
 291 {
 292     logslz(wakeup_beg, info);
 293     wakeup(info);
 294     logslz(wakeup_end, info);
 295 }