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Add a DCHECK for PlatformThread instances that are too busy.

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This adds a simple mechanism that provides protection against
implementations that use the legacy callback type in PlatformThread
and are prone to entering a busy loop.

Enabled only in DCHECK enabled builds.

BUG=webrtc:7187

Review-Url: https://codereview.webrtc.org/2720223003
Cr-Commit-Position: refs/heads/master@{#16973}
This commit is contained in:
tommi
2017-03-02 07:07:09 -08:00
committed by Commit bot
parent cabea3dbf2
commit 500f1b7a32
2 changed files with 53 additions and 7 deletions
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41
webrtc/base/platform_thread.cc
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@ -12,6 +12,7 @@
#include "webrtc/base/atomicops.h"
#include "webrtc/base/checks.h"
#include "webrtc/base/timeutils.h"
#if defined(WEBRTC_LINUX)
#include <sys/prctl.h>
@ -220,25 +221,53 @@ void PlatformThread::Run() {
run_function_(obj_);
return;
}
// TODO(tommi): Delete the below.
#if !defined(WEBRTC_MAC) && !defined(WEBRTC_WIN)
const struct timespec ts_null = {0};
// TODO(tommi): Delete the rest of this function when looping isn't supported.
#if RTC_DCHECK_IS_ON
// These constants control the busy loop detection algorithm below.
// |kMaxLoopCount| controls the limit for how many times we allow the loop
// to run within a period, before DCHECKing.
// |kPeriodToMeasureMs| controls how long that period is.
static const int kMaxLoopCount = 1000;
static const int kPeriodToMeasureMs = 100;
int64_t loop_stamps[kMaxLoopCount] = {};
int64_t sequence_nr = 0;
#endif
do {
// The interface contract of Start/Stop is that for a successful call to
// Start, there should be at least one call to the run function. So we
// call the function before checking |stop_|.
if (!run_function_deprecated_(obj_))
break;
#if RTC_DCHECK_IS_ON
auto id = sequence_nr % kMaxLoopCount;
loop_stamps[id] = rtc::TimeMillis();
if (sequence_nr > kMaxLoopCount) {
auto compare_id = (id + 1) % kMaxLoopCount;
auto diff = loop_stamps[id] - loop_stamps[compare_id];
RTC_DCHECK_GE(diff, 0);
if (diff < kPeriodToMeasureMs) {
RTC_NOTREACHED() << "This thread is too busy: " << name_ << " " << diff
<< "ms sequence=" << sequence_nr << " "
<< loop_stamps[id] << " vs " << loop_stamps[compare_id]
<< ", " << id << " vs " << compare_id;
}
}
++sequence_nr;
#endif
#if defined(WEBRTC_WIN)
// Alertable sleep to permit RaiseFlag to run and update |stop_|.
SleepEx(0, true);
} while (!stop_);
#else
#if defined(WEBRTC_MAC)
sched_yield();
#else
#if defined(UNDEFINED_SANITIZER) || defined(WEBRTC_ANDROID)
// UBSAN and Android don't like |sched_yield()| that much.
static const struct timespec ts_null = {0};
nanosleep(&ts_null, nullptr);
#else // !(defined(UNDEFINED_SANITIZER) || defined(WEBRTC_ANDROID))
// Mac and Linux show better performance with sched_yield.
sched_yield();
#endif
} while (!AtomicOps::AcquireLoad(&stop_flag_));
#endif // defined(WEBRTC_WIN)