third_party/tcmalloc/vendor/src/base/spinlock_linux-inl.h

   1 /* Copyright (c) 2009, Google Inc.
   2  * All rights reserved.
   3  *
   4  * Redistribution and use in source and binary forms, with or without
   5  * modification, are permitted provided that the following conditions are
   6  * met:
   7  *
   8  *     * Redistributions of source code must retain the above copyright
   9  * notice, this list of conditions and the following disclaimer.
  10  *     * Redistributions in binary form must reproduce the above
  11  * copyright notice, this list of conditions and the following disclaimer
  12  * in the documentation and/or other materials provided with the
  13  * distribution.
  14  *     * Neither the name of Google Inc. nor the names of its
  15  * contributors may be used to endorse or promote products derived from
  16  * this software without specific prior written permission.
  17  *
  18  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  19  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  20  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  21  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  22  * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  23  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  24  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  25  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  26  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  27  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  28  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  29  *
  30  * ---
  31  * This file is a Linux-specific part of spinlock_internal.cc
  32  */
  33
  34 #include <errno.h>
  35 #include <sched.h>
  36 #include <time.h>
  37 #include <limits.h>
  38 #include "base/linux_syscall_support.h"
  39
  40 #define FUTEX_WAIT 0
  41 #define FUTEX_WAKE 1
  42 #define FUTEX_PRIVATE_FLAG 128
  43
  44 static bool have_futex;
  45 static int futex_private_flag = FUTEX_PRIVATE_FLAG;
  46
  47 namespace {
  48 static struct InitModule {
  49   InitModule() {
  50     int x = 0;
  51     // futexes are ints, so we can use them only when
  52     // that's the same size as the lockword_ in SpinLock.
  53 #ifdef __arm__
  54     // ARM linux doesn't support sys_futex1(void*, int, int, struct timespec*);
  55     have_futex = 0;
  56 #else
  57     have_futex = (sizeof (Atomic32) == sizeof (int) &&
  58                   sys_futex(&x, FUTEX_WAKE, 1, 0) >= 0);
  59 #endif
  60     if (have_futex &&
  61         sys_futex(&x, FUTEX_WAKE | futex_private_flag, 1, 0) < 0) {
  62       futex_private_flag = 0;
  63     }
  64   }
  65 } init_module;
  66
  67 }  // anonymous namespace
  68
  69
  70 namespace base {
  71 namespace internal {
  72
  73 void SpinLockDelay(volatile Atomic32 *w, int32 value, int loop) {
  74   if (loop != 0) {
  75     int save_errno = errno;
  76     struct timespec tm;
  77     tm.tv_sec = 0;
  78     if (have_futex) {
  79       tm.tv_nsec = base::internal::SuggestedDelayNS(loop);
  80     } else {
  81       tm.tv_nsec = 2000001;   // above 2ms so linux 2.4 doesn't spin
  82     }
  83     if (have_futex) {
  84       tm.tv_nsec *= 16;  // increase the delay; we expect explicit wakeups
  85       sys_futex(reinterpret_cast<int *>(const_cast<Atomic32 *>(w)),
  86                 FUTEX_WAIT | futex_private_flag,
  87                 value, reinterpret_cast<struct kernel_timespec *>(&tm));
  88     } else {
  89       nanosleep(&tm, NULL);
  90     }
  91     errno = save_errno;
  92   }
  93 }
  94
  95 void SpinLockWake(volatile Atomic32 *w, bool all) {
  96   if (have_futex) {
  97     sys_futex(reinterpret_cast<int *>(const_cast<Atomic32 *>(w)),
  98               FUTEX_WAKE | futex_private_flag, all? INT_MAX : 1, 0);
  99   }
 100 }
 101
 102 } // namespace internal
 103 } // namespace base