Utilities/cmcurl/lib/easy_lock.h

   1 /***************************************************************************
   2  *                                  _   _ ____  _
   3  *  Project                     ___| | | |  _ \| |
   4  *                             / __| | | | |_) | |
   5  *                            | (__| |_| |  _ <| |___
   6  *                             \___|\___/|_| \_\_____|
   7  *
   8  * Copyright (C) 1998 - 2022, Daniel Stenberg, <daniel@haxx.se>, et al.
   9  *
  10  * This software is licensed as described in the file COPYING, which
  11  * you should have received as part of this distribution. The terms
  12  * are also available at https://curl.se/docs/copyright.html.
  13  *
  14  * You may opt to use, copy, modify, merge, publish, distribute and/or sell
  15  * copies of the Software, and permit persons to whom the Software is
  16  * furnished to do so, under the terms of the COPYING file.
  17  *
  18  * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
  19  * KIND, either express or implied.
  20  *
  21  * SPDX-License-Identifier: curl
  22  *
  23  ***************************************************************************/
  24
  25 #include "curl_setup.h"
  26
  27 #define GLOBAL_INIT_IS_THREADSAFE
  28
  29 #if defined(_WIN32_WINNT) && _WIN32_WINNT >= 0x600
  30
  31 #ifdef __MINGW32__
  32 #ifndef __MINGW64_VERSION_MAJOR
  33 #if (__MINGW32_MAJOR_VERSION < 5) || \
  34     (__MINGW32_MAJOR_VERSION == 5 && __MINGW32_MINOR_VERSION == 0)
  35 /* mingw >= 5.0.1 defines SRWLOCK, and slightly different from MS define */
  36 typedef PVOID SRWLOCK, *PSRWLOCK;
  37 #endif
  38 #endif
  39 #ifndef SRWLOCK_INIT
  40 #define SRWLOCK_INIT NULL
  41 #endif
  42 #endif /* __MINGW32__ */
  43
  44 #define curl_simple_lock SRWLOCK
  45 #define CURL_SIMPLE_LOCK_INIT SRWLOCK_INIT
  46
  47 #define curl_simple_lock_lock(m) AcquireSRWLockExclusive(m)
  48 #define curl_simple_lock_unlock(m) ReleaseSRWLockExclusive(m)
  49
  50 #elif defined(HAVE_ATOMIC) && defined(HAVE_STDATOMIC_H)
  51 #include <stdatomic.h>
  52 #if defined(HAVE_SCHED_YIELD)
  53 #include <sched.h>
  54 #endif
  55
  56 #define curl_simple_lock atomic_int
  57 #define CURL_SIMPLE_LOCK_INIT 0
  58
  59 /* a clang-thing */
  60 #ifndef __has_builtin
  61 #define __has_builtin(x) 0
  62 #endif
  63
  64 #ifndef __INTEL_COMPILER
  65 /* The Intel compiler tries to look like GCC *and* clang *and* lies in its
  66    __has_builtin() function, so override it. */
  67
  68 /* if GCC on i386/x86_64 or if the built-in is present */
  69 #if ( (defined(__GNUC__) && !defined(__clang__)) &&     \
  70       (defined(__i386__) || defined(__x86_64__))) ||    \
  71   __has_builtin(__builtin_ia32_pause)
  72 #define HAVE_BUILTIN_IA32_PAUSE
  73 #endif
  74
  75 #endif
  76
  77 static inline void curl_simple_lock_lock(curl_simple_lock *lock)
  78 {
  79   for(;;) {
  80     if(!atomic_exchange_explicit(lock, true, memory_order_acquire))
  81       break;
  82     /* Reduce cache coherency traffic */
  83     while(atomic_load_explicit(lock, memory_order_relaxed)) {
  84       /* Reduce load (not mandatory) */
  85 #ifdef HAVE_BUILTIN_IA32_PAUSE
  86       __builtin_ia32_pause();
  87 #elif defined(__aarch64__)
  88       __asm__ volatile("yield" ::: "memory");
  89 #elif defined(HAVE_SCHED_YIELD)
  90       sched_yield();
  91 #endif
  92     }
  93   }
  94 }
  95
  96 static inline void curl_simple_lock_unlock(curl_simple_lock *lock)
  97 {
  98   atomic_store_explicit(lock, false, memory_order_release);
  99 }
 100
 101 #else
 102
 103 #undef  GLOBAL_INIT_IS_THREADSAFE
 104
 105 #endif