am 7a67c335: Merge "Modify the code to avoid potential deadlocks." (acd574c1) · Commits · e / os / android_system_core

libbacktrace/BacktraceCurrent.cpp

+28 −12

Original line number	Diff line number	Diff line
		@@ -96,7 +96,7 @@ static pthread_mutex_t g_sigaction_mutex = PTHREAD_MUTEX_INITIALIZER;
		static void SignalHandler(int, siginfo_t, void sigcontext) {
		ThreadEntry* entry = ThreadEntry::Get(getpid(), gettid(), false);
		if (!entry) {
		BACK_LOGW("Unable to find pid %d tid %d information", getpid(), gettid());
		BACK_LOGE("pid %d, tid %d entry not found", getpid(), gettid());
		return;
		}

		@@ -109,9 +109,14 @@ static void SignalHandler(int, siginfo_t, void sigcontext) {
		// the thread run ahead causing problems.
		// The number indicates that we are waiting for the second Wake() call
		// overall which is made by the thread requesting an unwind.
		entry->Wait(2);

		ThreadEntry::Remove(entry);
		if (entry->Wait(2)) {
		// Do not remove the entry here because that can result in a deadlock
		// if the code cannot properly send a signal to the thread under test.
		entry->Wake();
		} else {
		// At this point, it is possible that entry has been freed, so just exit.
		BACK_LOGE("Timed out waiting for unwind thread to indicate it completed.");
		}
		}

		bool BacktraceCurrent::UnwindThread(size_t num_ignore_frames) {
		@@ -128,17 +133,15 @@ bool BacktraceCurrent::UnwindThread(size_t num_ignore_frames) {
		act.sa_flags = SA_RESTART \| SA_SIGINFO \| SA_ONSTACK;
		sigemptyset(&act.sa_mask);
		if (sigaction(THREAD_SIGNAL, &act, &oldact) != 0) {
		BACK_LOGW("sigaction failed %s", strerror(errno));
		entry->Unlock();
		BACK_LOGE("sigaction failed: %s", strerror(errno));
		ThreadEntry::Remove(entry);
		pthread_mutex_unlock(&g_sigaction_mutex);
		return false;
		}

		if (tgkill(Pid(), Tid(), THREAD_SIGNAL) != 0) {
		BACK_LOGW("tgkill %d failed: %s", Tid(), strerror(errno));
		BACK_LOGE("tgkill %d failed: %s", Tid(), strerror(errno));
		sigaction(THREAD_SIGNAL, &oldact, nullptr);
		entry->Unlock();
		ThreadEntry::Remove(entry);
		pthread_mutex_unlock(&g_sigaction_mutex);
		return false;
		@@ -146,17 +149,30 @@ bool BacktraceCurrent::UnwindThread(size_t num_ignore_frames) {

		// Wait for the thread to get the ucontext. The number indicates
		// that we are waiting for the first Wake() call made by the thread.
		entry->Wait(1);
		bool wait_completed = entry->Wait(1);

		// After the thread has received the signal, allow other unwinders to
		// continue.
		sigaction(THREAD_SIGNAL, &oldact, nullptr);
		pthread_mutex_unlock(&g_sigaction_mutex);

		bool unwind_done = UnwindFromContext(num_ignore_frames, entry->GetUcontext());
		bool unwind_done = false;
		if (wait_completed) {
		unwind_done = UnwindFromContext(num_ignore_frames, entry->GetUcontext());

		// Tell the signal handler to exit and release the entry.
		entry->Wake();

		// Wait for the thread to indicate it is done with the ThreadEntry.
		if (!entry->Wait(3)) {
		// Send a warning, but do not mark as a failure to unwind.
		BACK_LOGW("Timed out waiting for signal handler to indicate it finished.");
		}
		} else {
		BACK_LOGE("Timed out waiting for signal handler to get ucontext data.");
		}

		ThreadEntry::Remove(entry);

		return unwind_done;
		}

libbacktrace/BacktraceLog.h

+3 −0

Original line number	Diff line number	Diff line
		@@ -25,4 +25,7 @@
		#define BACK_LOGW(format, ...) \
		ALOGW("%s: " format, __PRETTY_FUNCTION__, ##__VA_ARGS__)

		#define BACK_LOGE(format, ...) \
		ALOGE("%s: " format, __PRETTY_FUNCTION__, ##__VA_ARGS__)

		#endif // _LIBBACKTRACE_BACKTRACE_LOG_H

libbacktrace/ThreadEntry.cpp

+8 −4

Original line number	Diff line number	Diff line
		@@ -69,7 +69,7 @@ ThreadEntry* ThreadEntry::Get(pid_t pid, pid_t tid, bool create) {
		}

		void ThreadEntry::Remove(ThreadEntry* entry) {
		pthread_mutex_unlock(&entry->mutex_);
		entry->Unlock();

		pthread_mutex_lock(&ThreadEntry::list_mutex_);
		if (--entry->ref_count_ == 0) {
		@@ -96,20 +96,24 @@ ThreadEntry::~ThreadEntry() {
		pthread_cond_destroy(&wait_cond_);
		}

		void ThreadEntry::Wait(int value) {
		bool ThreadEntry::Wait(int value) {
		timespec ts;
		clock_gettime(CLOCK_MONOTONIC, &ts);
		ts.tv_sec += 10;
		ts.tv_sec += 5;

		bool wait_completed = true;
		pthread_mutex_lock(&wait_mutex_);
		while (wait_value_ != value) {
		int ret = pthread_cond_timedwait(&wait_cond_, &wait_mutex_, &ts);
		if (ret != 0) {
		BACK_LOGW("pthread_cond_timedwait failed: %s", strerror(ret));
		BACK_LOGW("pthread_cond_timedwait for value %d failed: %s", value, strerror(ret));
		wait_completed = false;
		break;
		}
		}
		pthread_mutex_unlock(&wait_mutex_);

		return wait_completed;
		}

		void ThreadEntry::Wake() {

libbacktrace/ThreadEntry.h

+1 −1

Original line number	Diff line number	Diff line
		@@ -29,7 +29,7 @@ public:

		void Wake();

		void Wait(int);
		bool Wait(int);

		void CopyUcontextFromSigcontext(void*);