1/*
2 * Copyright 2015 Google Inc.
3 *
4 * Use of this source code is governed by a BSD-style license that can be
5 * found in the LICENSE file.
6 */
7
8#include "include/private/SkSpinlock.h"
9#include "include/private/SkThreadAnnotations.h"
10
11#if 0
12 #include "include/private/SkMutex.h"
13 #include <execinfo.h>
14 #include <stdio.h>
15
16 static void debug_trace() {
17 void* stack[64];
18 int len = backtrace(stack, SK_ARRAY_COUNT(stack));
19
20 // As you might imagine, we can't use an SkSpinlock here...
21 static SkMutex lock;
22 {
23 SkAutoMutexExclusive locked(lock);
24 fprintf(stderr, "\n");
25 backtrace_symbols_fd(stack, len, 2/*stderr*/);
26 fprintf(stderr, "\n");
27 }
28 }
29#else
30 static void debug_trace() {}
31#endif
32
33// Renamed from "pause" to avoid conflict with function defined in unistd.h
34#if SK_CPU_SSE_LEVEL >= SK_CPU_SSE_LEVEL_SSE2
35 #include <emmintrin.h>
36 static void do_pause() { _mm_pause(); }
37#else
38 static void do_pause() { /*spin*/ }
39#endif
40
41void SkSpinlock::contendedAcquire() {
42 debug_trace();
43
44 // To act as a mutex, we need an acquire barrier when we acquire the lock.
45 SK_POTENTIALLY_BLOCKING_REGION_BEGIN;
46 while (fLocked.exchange(true, std::memory_order_acquire)) {
47 do_pause();
48 }
49 SK_POTENTIALLY_BLOCKING_REGION_END;
50}
51