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Fix AV in host from tracing on exit #77425

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Merged
merged 3 commits into from
Oct 28, 2022
Merged

Fix AV in host from tracing on exit #77425

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6bbf9c1
Fix AV in host from tracing on exit
elinor-fung Oct 25, 2022
902f893
Use spin lock
elinor-fung Oct 25, 2022
f0122a7
Yield when spinning
elinor-fung Oct 26, 2022
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47 changes: 39 additions & 8 deletions src/native/corehost/hostmisc/trace.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -3,6 +3,7 @@

#include "trace.h"
#include <mutex>
#include <thread>

// g_trace_verbosity is used to encode COREHOST_TRACE and COREHOST_TRACE_VERBOSITY to selectively control output of
// trace::warn(), trace::info(), and trace::verbose()
Expand All @@ -13,9 +14,39 @@
// COREHOST_TRACE=1 COREHOST_TRACE_VERBOSITY=1 implies g_trace_verbosity = 1. // Trace "enabled". error() messages will be produced
static int g_trace_verbosity = 0;
static FILE * g_trace_file = stderr;
static pal::mutex_t g_trace_mutex;
thread_local static trace::error_writer_fn g_error_writer = nullptr;

namespace
{
class spin_lock
{
public:
spin_lock() = default;
spin_lock(const spin_lock&) = delete;
spin_lock& operator=(const spin_lock&) = delete;

void lock()
{
uint32_t spin = 0;
while (flag.test_and_set(std::memory_order_acquire))
{
if (spin++ % 1024 == 0)
std::this_thread::yield();
}
}

void unlock()
{
flag.clear(std::memory_order_release);
}

private:
std::atomic_flag flag = ATOMIC_FLAG_INIT;
};

spin_lock g_trace_lock;
}

//
// Turn on tracing for the corehost based on "COREHOST_TRACE" & "COREHOST_TRACEFILE" env.
//
Expand Down Expand Up @@ -50,7 +81,7 @@ bool trace::enable()
}
else
{
std::lock_guard<pal::mutex_t> lock(g_trace_mutex);
std::lock_guard<spin_lock> lock(g_trace_lock);

g_trace_file = stderr;
if (pal::getenv(_X("COREHOST_TRACEFILE"), &tracefile_str))
Expand Down Expand Up @@ -95,7 +126,7 @@ void trace::verbose(const pal::char_t* format, ...)
{
if (g_trace_verbosity > 3)
{
std::lock_guard<pal::mutex_t> lock(g_trace_mutex);
std::lock_guard<spin_lock> lock(g_trace_lock);

va_list args;
va_start(args, format);
Expand All @@ -108,7 +139,7 @@ void trace::info(const pal::char_t* format, ...)
{
if (g_trace_verbosity > 2)
{
std::lock_guard<pal::mutex_t> lock(g_trace_mutex);
std::lock_guard<spin_lock> lock(g_trace_lock);

va_list args;
va_start(args, format);
Expand All @@ -119,7 +150,7 @@ void trace::info(const pal::char_t* format, ...)

void trace::error(const pal::char_t* format, ...)
{
std::lock_guard<pal::mutex_t> lock(g_trace_mutex);
std::lock_guard<spin_lock> lock(g_trace_lock);

// Always print errors
va_list args;
Expand Down Expand Up @@ -156,7 +187,7 @@ void trace::error(const pal::char_t* format, ...)

void trace::println(const pal::char_t* format, ...)
{
std::lock_guard<pal::mutex_t> lock(g_trace_mutex);
std::lock_guard<spin_lock> lock(g_trace_lock);

va_list args;
va_start(args, format);
Expand All @@ -173,7 +204,7 @@ void trace::warning(const pal::char_t* format, ...)
{
if (g_trace_verbosity > 1)
{
std::lock_guard<pal::mutex_t> lock(g_trace_mutex);
std::lock_guard<spin_lock> lock(g_trace_lock);

va_list args;
va_start(args, format);
Expand All @@ -184,7 +215,7 @@ void trace::warning(const pal::char_t* format, ...)

void trace::flush()
{
std::lock_guard<pal::mutex_t> lock(g_trace_mutex);
std::lock_guard<spin_lock> lock(g_trace_lock);

pal::file_flush(g_trace_file);
pal::err_flush();
Expand Down