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/thread2.h>
  52 #include <sys/serialize.h>
  53 #include <sys/sysctl.h>
  54 #include <sys/ktr.h>
  55 #include <sys/kthread.h>
  56 #include <machine/cpu.h>
  57 #include <machine/cpufunc.h>
  58 #include <machine/specialreg.h>
  59 #include <machine/clock.h>
  60 #include <sys/lock.h>
  61
  62 #ifndef SLZ_ADAPTIVE_SPINMAX
  63 #define SLZ_ADAPTIVE_SPINMAX    4096
  64 #endif
  65
  66 #define SLZ_KTR_STRING          "slz=%p"
  67 #define SLZ_KTR_ARGS            lwkt_serialize_t slz
  68
  69 #ifndef KTR_SERIALIZER
  70 #define KTR_SERIALIZER          KTR_ALL
  71 #endif
  72
  73 KTR_INFO_MASTER(slz);
  74 KTR_INFO(KTR_SERIALIZER, slz, enter_beg, 0, SLZ_KTR_STRING, SLZ_KTR_ARGS);
  75 KTR_INFO(KTR_SERIALIZER, slz, sleep_beg, 1, SLZ_KTR_STRING, SLZ_KTR_ARGS);
  76 KTR_INFO(KTR_SERIALIZER, slz, sleep_end, 2, SLZ_KTR_STRING, SLZ_KTR_ARGS);
  77 KTR_INFO(KTR_SERIALIZER, slz, exit_end, 3, SLZ_KTR_STRING, SLZ_KTR_ARGS);
  78 KTR_INFO(KTR_SERIALIZER, slz, wakeup_beg, 4, SLZ_KTR_STRING, SLZ_KTR_ARGS);
  79 KTR_INFO(KTR_SERIALIZER, slz, wakeup_end, 5, SLZ_KTR_STRING, SLZ_KTR_ARGS);
  80 KTR_INFO(KTR_SERIALIZER, slz, try, 6, SLZ_KTR_STRING, SLZ_KTR_ARGS);
  81 KTR_INFO(KTR_SERIALIZER, slz, tryfail, 7, SLZ_KTR_STRING, SLZ_KTR_ARGS);
  82 KTR_INFO(KTR_SERIALIZER, slz, tryok, 8, SLZ_KTR_STRING, SLZ_KTR_ARGS);
  83 KTR_INFO(KTR_SERIALIZER, slz, enter_end, 9, SLZ_KTR_STRING, SLZ_KTR_ARGS);
  84 KTR_INFO(KTR_SERIALIZER, slz, exit_beg, 10, SLZ_KTR_STRING, SLZ_KTR_ARGS);
  85 KTR_INFO(KTR_SERIALIZER, slz, adapt_beg, 11, SLZ_KTR_STRING, SLZ_KTR_ARGS);
  86 KTR_INFO(KTR_SERIALIZER, slz, adapt_end, 12, SLZ_KTR_STRING, SLZ_KTR_ARGS);
  87 KTR_INFO(KTR_SERIALIZER, slz, adapt_spinend, 13, "slz=%p try=%d",
  88     lwkt_serialize_t slz, int try);
  89 KTR_INFO(KTR_SERIALIZER, slz, adapt_sleepb, 14, SLZ_KTR_STRING, SLZ_KTR_ARGS);
  90 KTR_INFO(KTR_SERIALIZER, slz, adapt_sleepe, 15, SLZ_KTR_STRING, SLZ_KTR_ARGS);
  91
  92 #define logslz(name, slz)               KTR_LOG(slz_ ## name, slz)
  93 #define logslz_spinend(slz, try)        KTR_LOG(slz_adapt_spinend, slz, try)
  94
  95 static void lwkt_serialize_sleep(void *info);
  96 static void lwkt_serialize_wakeup(void *info);
  97
  98 void
  99 lwkt_serialize_init(lwkt_serialize_t s)
 100 {
 101     atomic_intr_init(&s->interlock);
 102     s->last_td = (void *)-4;
 103 }
 104
 105 void
 106 lwkt_serialize_enter(lwkt_serialize_t s)
 107 {
 108     ASSERT_NOT_SERIALIZED(s);
 109
 110     logslz(enter_beg, s);
 111     atomic_intr_cond_enter(&s->interlock, lwkt_serialize_sleep, s);
 112     logslz(enter_end, s);
 113     s->last_td = curthread;
 114 }
 115
 116 /*
 117  * Returns non-zero on success
 118  */
 119 int
 120 lwkt_serialize_try(lwkt_serialize_t s)
 121 {
 122     int error;
 123
 124     ASSERT_NOT_SERIALIZED(s);
 125
 126     logslz(try, s);
 127     if ((error = atomic_intr_cond_try(&s->interlock)) == 0) {
 128         s->last_td = curthread;
 129         logslz(tryok, s);
 130         return(1);
 131     }
 132     logslz(tryfail, s);
 133     return (0);
 134 }
 135
 136 void
 137 lwkt_serialize_exit(lwkt_serialize_t s)
 138 {
 139     ASSERT_SERIALIZED(s);
 140     s->last_td = (void *)-2;
 141     logslz(exit_beg, s);
 142     atomic_intr_cond_exit(&s->interlock, lwkt_serialize_wakeup, s);
 143     logslz(exit_end, s);
 144 }
 145
 146 /*
 147  * Interrupt handler disablement support, used by drivers.  Non-stackable
 148  * (uses bit 30).
 149  */
 150 void
 151 lwkt_serialize_handler_disable(lwkt_serialize_t s)
 152 {
 153     atomic_intr_handler_disable(&s->interlock);
 154 }
 155
 156 void
 157 lwkt_serialize_handler_enable(lwkt_serialize_t s)
 158 {
 159     atomic_intr_handler_enable(&s->interlock);
 160 }
 161
 162 void
 163 lwkt_serialize_handler_call(lwkt_serialize_t s, void (*func)(void *, void *),
 164                             void *arg, void *frame)
 165 {
 166     /*
 167      * note: a return value of 0 indicates that the interrupt handler is
 168      * enabled.
 169      */
 170     if (atomic_intr_handler_is_enabled(&s->interlock) == 0) {
 171         logslz(enter_beg, s);
 172         atomic_intr_cond_enter(&s->interlock, lwkt_serialize_sleep, s);
 173         logslz(enter_end, s);
 174         s->last_td = curthread;
 175         if (atomic_intr_handler_is_enabled(&s->interlock) == 0)
 176             func(arg, frame);
 177
 178         ASSERT_SERIALIZED(s);
 179         s->last_td = (void *)-2;
 180         logslz(exit_beg, s);
 181         atomic_intr_cond_exit(&s->interlock, lwkt_serialize_wakeup, s);
 182         logslz(exit_end, s);
 183     }
 184 }
 185
 186 /*
 187  * Similar to handler_call but does not block.  Returns 0 on success,
 188  * and 1 on failure.
 189  */
 190 int
 191 lwkt_serialize_handler_try(lwkt_serialize_t s, void (*func)(void *, void *),
 192                            void *arg, void *frame)
 193 {
 194     /*
 195      * note: a return value of 0 indicates that the interrupt handler is
 196      * enabled.
 197      */
 198     if (atomic_intr_handler_is_enabled(&s->interlock) == 0) {
 199         logslz(try, s);
 200         if (atomic_intr_cond_try(&s->interlock) == 0) {
 201             s->last_td = curthread;
 202             logslz(tryok, s);
 203
 204             func(arg, frame);
 205
 206             ASSERT_SERIALIZED(s);
 207             s->last_td = (void *)-2;
 208             logslz(exit_beg, s);
 209             atomic_intr_cond_exit(&s->interlock, lwkt_serialize_wakeup, s);
 210             logslz(exit_end, s);
 211             return(0);
 212         }
 213     }
 214     logslz(tryfail, s);
 215     return(1);
 216 }
 217
 218
 219 /*
 220  * Helper functions
 221  *
 222  * It is possible to race an interrupt which acquires and releases the
 223  * bit, then calls wakeup before we actually go to sleep, so we
 224  * need to check that the interlock is still acquired from within
 225  * a critical section prior to sleeping.
 226  */
 227 static void
 228 lwkt_serialize_sleep(void *info)
 229 {
 230     lwkt_serialize_t s = info;
 231
 232     tsleep_interlock(s, 0);
 233     if (atomic_intr_cond_test(&s->interlock) != 0) {
 234         logslz(sleep_beg, s);
 235         tsleep(s, PINTERLOCKED, "slize", 0);
 236         logslz(sleep_end, s);
 237     }
 238 }
 239
 240 void
 241 lwkt_serialize_adaptive_enter(lwkt_serialize_t s)
 242 {
 243     int try;
 244
 245     ASSERT_NOT_SERIALIZED(s);
 246     logslz(adapt_beg, s);
 247
 248     if (atomic_intr_cond_try(&s->interlock) == 0) {
 249         s->last_td = curthread;
 250         logslz(adapt_end, s);
 251         return;
 252     }
 253
 254 restart:
 255     /*
 256      * Spinning a little bit, before going to sleep
 257      *
 258      * See the comment before kern/kern_spinlock.c
 259      * _spin_lock_contested() about why atomic_intr_cond_test()
 260      * is called first.  atomic_intr_cond_test() contains
 261      * _no_ MPLOCKED intruction.
 262      */
 263     for (try = SLZ_ADAPTIVE_SPINMAX; try; --try) {
 264         if (atomic_intr_cond_test(&s->interlock) == 0 &&
 265             atomic_intr_cond_try(&s->interlock) == 0) {
 266             s->last_td = curthread;
 267             logslz_spinend(s, try);
 268             return;
 269         }
 270     }
 271
 272     atomic_intr_cond_inc(&s->interlock);
 273
 274     tsleep_interlock(s, 0);
 275     if (atomic_intr_cond_try(&s->interlock) == 0) {
 276         atomic_intr_cond_dec(&s->interlock);
 277         s->last_td = curthread;
 278         logslz_spinend(s, 0);
 279         return;
 280     } else {
 281         logslz(adapt_sleepb, s);
 282         tsleep(s, PINTERLOCKED, "aslize", 0);
 283         logslz(adapt_sleepe, s);
 284
 285         atomic_intr_cond_dec(&s->interlock);
 286         goto restart;
 287     }
 288 }
 289
 290 static void
 291 lwkt_serialize_wakeup(void *info)
 292 {
 293     logslz(wakeup_beg, info);
 294     wakeup(info);
 295     logslz(wakeup_end, info);
 296 }