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// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.
#include "common.h"
#include "sampleprofiler.h"
#include "hosting.h"
#include "threadsuspend.h"
Volatile<BOOL> SampleProfiler::s_profilingEnabled = false;
Thread* SampleProfiler::s_pSamplingThread = NULL;
CLREventStatic SampleProfiler::s_threadShutdownEvent;
#ifdef FEATURE_PAL
long SampleProfiler::s_samplingRateInNs = 1000000; // 1ms
#endif
// Synchronization of multiple callers occurs in EventPipe::Enable.
void SampleProfiler::Enable()
{
CONTRACTL
{
THROWS;
GC_TRIGGERS;
MODE_ANY;
PRECONDITION(s_pSamplingThread == NULL);
}
CONTRACTL_END;
s_profilingEnabled = true;
s_pSamplingThread = SetupUnstartedThread();
if(s_pSamplingThread->CreateNewThread(0, ThreadProc, NULL))
{
// Start the sampling thread.
s_pSamplingThread->SetBackground(TRUE);
s_pSamplingThread->StartThread();
}
else
{
_ASSERT(!"Unable to create sample profiler thread.");
}
}
// Synchronization of multiple callers occurs in EventPipe::Disable.
void SampleProfiler::Disable()
{
CONTRACTL
{
THROWS;
GC_TRIGGERS;
MODE_ANY;
}
CONTRACTL_END;
// Bail early if profiling is not enabled.
if(!s_profilingEnabled)
{
return;
}
// Reset the event before shutdown.
s_threadShutdownEvent.Reset();
// The sampling thread will watch this value and exit
// when profiling is disabled.
s_profilingEnabled = false;
// Wait for the sampling thread to clean itself up.
s_threadShutdownEvent.Wait(0, FALSE /* bAlertable */);
}
DWORD WINAPI SampleProfiler::ThreadProc(void *args)
{
CONTRACTL
{
NOTHROW;
GC_TRIGGERS;
MODE_PREEMPTIVE;
PRECONDITION(s_pSamplingThread != NULL);
}
CONTRACTL_END;
// Complete thread initialization and start the profiling loop.
if(s_pSamplingThread->HasStarted())
{
// Switch to pre-emptive mode so that this thread doesn't starve the GC.
GCX_PREEMP();
while(s_profilingEnabled)
{
// Check to see if we can suspend managed execution.
if(ThreadSuspend::SysIsSuspendInProgress() || (ThreadSuspend::GetSuspensionThread() != 0))
{
// Skip the current sample.
#ifdef FEATURE_PAL
PAL_nanosleep(s_samplingRateInNs);
#else
ClrSleepEx(1, FALSE);
#endif
continue;
}
// Actually suspend managed execution.
ThreadSuspend::SuspendEE(ThreadSuspend::SUSPEND_REASON::SUSPEND_OTHER);
// Walk all managed threads and capture stacks.
WalkManagedThreads();
// Resume managed execution.
ThreadSuspend::RestartEE(FALSE /* bFinishedGC */, TRUE /* SuspendSucceeded */);
// Wait until it's time to sample again.
#ifdef FEATURE_PAL
PAL_nanosleep(s_samplingRateInNs);
#else
ClrSleepEx(1, FALSE);
#endif
}
}
// Destroy the sampling thread when done running.
DestroyThread(s_pSamplingThread);
s_pSamplingThread = NULL;
// Signal Disable() that the thread has been destroyed.
s_threadShutdownEvent.Set();
return S_OK;
}
// The thread store lock must already be held by the thread before this function
// is called. ThreadSuspend::SuspendEE acquires the thread store lock.
void SampleProfiler::WalkManagedThreads()
{
CONTRACTL
{
NOTHROW;
GC_TRIGGERS;
MODE_PREEMPTIVE;
}
CONTRACTL_END;
Thread *pThread = NULL;
StackContents stackContents;
// Iterate over all managed threads.
// Assumes that the ThreadStoreLock is held because we've suspended all threads.
while ((pThread = ThreadStore::GetThreadList(pThread)) != NULL)
{
// Walk the stack and write it out as an event.
if(EventPipe::WalkManagedStackForThread(pThread, stackContents) && !stackContents.IsEmpty())
{
EventPipe::WriteSampleProfileEvent(pThread, stackContents);
}
}
}
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