yuzu/externals/cubeb/test/test_deadlock.cpp

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2020-12-28 19:15:37 +04:00
/*
* Copyright © 2017 Mozilla Foundation
*
* This program is made available under an ISC-style license. See the
* accompanying file LICENSE for details.
*
*
* Purpose
* =============================================================================
* In CoreAudio, the data callback will holds a mutex shared with AudioUnit
* (mutex_AU). Thus, if the callback request another mutex M held by the another
* function, without releasing mutex_AU, then it will cause a deadlock when the
* another function, which holds the mutex M, request to use AudioUnit.
*
* The following figure illustrates the deadlock in bug 1337805:
* https://bugzilla.mozilla.org/show_bug.cgi?id=1337805
* (The detail analysis can be found on bug 1350511:
* https://bugzilla.mozilla.org/show_bug.cgi?id=1350511)
*
* holds
* data_callback <---------- mutext_AudioUnit(mutex_AU)
* | ^
* | |
* | request | request
* | |
* v holds |
* mutex_cubeb ------------> get_channel_layout
*
* In this example, the "audiounit_get_channel_layout" in f4edfb8:
* https://github.com/kinetiknz/cubeb/blob/f4edfb8eea920887713325e44773f3a2d959860c/src/cubeb_audiounit.cpp#L2725
* requests the mutex_AU to create an AudioUnit, when it holds a mutex for cubeb
* context. Meanwhile, the data callback who holds the mutex_AU requests the
* mutex for cubeb context. As a result, it causes a deadlock.
*
* The problem is solve by pull 236: https://github.com/kinetiknz/cubeb/pull/236
* We store the latest channel layout and return it when there is an active
* AudioUnit, otherwise, we will create an AudioUnit to get it.
*
* Although the problem is solved, to prevent it happens again, we add the test
* here in case someone without such knowledge misuses the AudioUnit in
* get_channel_layout. Moreover, it's a good way to record the known issues
* to warn other developers.
*/
#include "gtest/gtest.h"
//#define ENABLE_NORMAL_LOG
//#define ENABLE_VERBOSE_LOG
#include "common.h" // for layout_infos
#include "cubeb/cubeb.h" // for cubeb utils
#include "cubeb_utils.h" // for owned_critical_section, auto_lock
#include <iostream> // for fprintf
#include <pthread.h> // for pthread
#include <signal.h> // for signal
#include <stdexcept> // for std::logic_error
#include <string> // for std::string
#include <unistd.h> // for sleep, usleep
#include <atomic> // for std::atomic
// The signal alias for calling our thread killer.
#define CALL_THREAD_KILLER SIGUSR1
// This indicator will become true when our pending task thread is killed by
// ourselves.
bool killed = false;
// This indicator will become true when the assigned task is done.
std::atomic<bool> task_done{ false };
// Indicating the data callback is fired or not.
bool called = false;
// Toggle to true when running data callback. Before data callback gets
// the mutex for cubeb context, it toggles back to false.
// The task to get channel layout should be executed when this is true.
std::atomic<bool> callbacking_before_getting_context{ false };
owned_critical_section context_mutex;
cubeb * context = nullptr;
cubeb * get_cubeb_context_unlocked()
{
if (context) {
return context;
}
int r = CUBEB_OK;
r = common_init(&context, "Cubeb deadlock test");
if (r != CUBEB_OK) {
context = nullptr;
}
return context;
}
cubeb * get_cubeb_context()
{
auto_lock lock(context_mutex);
return get_cubeb_context_unlocked();
}
void state_cb_audio(cubeb_stream * /*stream*/, void * /*user*/, cubeb_state /*state*/)
{
}
// Fired by coreaudio's rendering mechanism. It holds a mutex shared with the
// current used AudioUnit.
template<typename T>
long data_cb(cubeb_stream * /*stream*/, void * /*user*/,
const void * /*inputbuffer*/, void * outputbuffer, long nframes)
{
called = true;
uint64_t tid; // Current thread id.
pthread_threadid_np(NULL, &tid);
fprintf(stderr, "Audio output is on thread %llu\n", tid);
if (!task_done) {
callbacking_before_getting_context = true;
fprintf(stderr, "[%llu] time to switch thread\n", tid);
// Force to switch threads by sleeping 10 ms. Notice that anything over
// 10ms would create a glitch. It's intended here for test, so the delay
// is ok.
usleep(10000);
callbacking_before_getting_context = false;
}
fprintf(stderr, "[%llu] try getting backend id ...\n", tid);
// Try requesting mutex for context by get_cubeb_context()
// when holding a mutex for AudioUnit.
char const * backend_id = cubeb_get_backend_id(get_cubeb_context());
fprintf(stderr, "[%llu] callback on %s\n", tid, backend_id);
// Mute the output (or get deaf)
memset(outputbuffer, 0, nframes * 2 * sizeof(float));
return nframes;
}
// Called by wait_to_get_layout, which is run out of main thread.
void get_preferred_channel_layout()
{
auto_lock lock(context_mutex);
cubeb * context = get_cubeb_context_unlocked();
ASSERT_TRUE(!!context);
// We will cause a deadlock if cubeb_get_preferred_channel_layout requests
// mutex for AudioUnit when it holds mutex for context.
cubeb_channel_layout layout;
int r = cubeb_get_preferred_channel_layout(context, &layout);
ASSERT_EQ(r == CUBEB_OK, layout != CUBEB_LAYOUT_UNDEFINED);
fprintf(stderr, "layout is %s\n", layout_infos[layout].name);
}
void * wait_to_get_layout(void *)
{
uint64_t tid; // Current thread id.
pthread_threadid_np(NULL, &tid);
while(!callbacking_before_getting_context) {
fprintf(stderr, "[%llu] waiting for data callback ...\n", tid);
usleep(1000); // Force to switch threads by sleeping 1 ms.
}
fprintf(stderr, "[%llu] try getting channel layout ...\n", tid);
get_preferred_channel_layout(); // Deadlock checkpoint.
task_done = true;
return NULL;
}
void * watchdog(void * s)
{
uint64_t tid; // Current thread id.
pthread_threadid_np(NULL, &tid);
pthread_t subject = *((pthread_t *) s);
uint64_t stid; // task thread id.
pthread_threadid_np(subject, &stid);
unsigned int sec = 2;
fprintf(stderr, "[%llu] sleep %d seconds before checking task for thread %llu\n", tid, sec, stid);
sleep(sec); // Force to switch threads.
fprintf(stderr, "[%llu] check task for thread %llu now\n", tid, stid);
if (!task_done) {
fprintf(stderr, "[%llu] kill the task thread %llu\n", tid, stid);
pthread_kill(subject, CALL_THREAD_KILLER);
pthread_detach(subject);
// pthread_kill doesn't release the mutex held by the killed thread,
// so we need to unlock it manually.
context_mutex.unlock();
}
fprintf(stderr, "[%llu] the assigned task for thread %llu is %sdone\n", tid, stid, (task_done) ? "" : "not ");
return NULL;
}
void thread_killer(int signal)
{
ASSERT_EQ(signal, CALL_THREAD_KILLER);
fprintf(stderr, "task thread is killed!\n");
killed = true;
}
TEST(cubeb, run_deadlock_test)
{
#if !defined(__APPLE__)
FAIL() << "Deadlock test is only for OSX now";
#endif
cubeb * ctx = get_cubeb_context();
ASSERT_TRUE(!!ctx);
std::unique_ptr<cubeb, decltype(&cubeb_destroy)>
cleanup_cubeb_at_exit(ctx, cubeb_destroy);
cubeb_stream_params params;
params.format = CUBEB_SAMPLE_FLOAT32NE;
params.rate = 44100;
params.channels = 2;
params.layout = CUBEB_LAYOUT_STEREO;
params.prefs = CUBEB_STREAM_PREF_NONE;
cubeb_stream * stream = NULL;
int r = cubeb_stream_init(ctx, &stream, "test deadlock", NULL, NULL, NULL,
&params, 512, &data_cb<float>, state_cb_audio, NULL);
ASSERT_EQ(r, CUBEB_OK);
std::unique_ptr<cubeb_stream, decltype(&cubeb_stream_destroy)>
cleanup_stream_at_exit(stream, cubeb_stream_destroy);
// Install signal handler.
signal(CALL_THREAD_KILLER, thread_killer);
pthread_t subject, detector;
pthread_create(&subject, NULL, wait_to_get_layout, NULL);
pthread_create(&detector, NULL, watchdog, (void *) &subject);
uint64_t stid, dtid;
pthread_threadid_np(subject, &stid);
pthread_threadid_np(detector, &dtid);
fprintf(stderr, "task thread %llu, monitor thread %llu are created\n", stid, dtid);
cubeb_stream_start(stream);
pthread_join(subject, NULL);
pthread_join(detector, NULL);
ASSERT_TRUE(called);
fprintf(stderr, "\n%sDeadlock detected!\n", (called && !task_done.load()) ? "" : "No ");
// Check the task is killed by ourselves if deadlock happends.
// Otherwise, thread_killer should not be triggered.
ASSERT_NE(task_done.load(), killed);
ASSERT_TRUE(task_done.load());
cubeb_stream_stop(stream);
}