Merge "Minor robustness tweaks." (de8b136d) · Commits · e / os / android_system_core

libcorkscrew/backtrace.c

+52 −12

Original line number	Diff line number	Diff line
		@@ -85,9 +85,13 @@ ssize_t unwind_backtrace(backtrace_frame_t* backtrace, size_t ignore_depth, size
		}

		#ifdef CORKSCREW_HAVE_ARCH
		static const int32_t STATE_DUMPING = -1;
		static const int32_t STATE_DONE = -2;
		static const int32_t STATE_CANCEL = -3;

		static pthread_mutex_t g_unwind_signal_mutex = PTHREAD_MUTEX_INITIALIZER;
		static volatile struct {
		int32_t tid;
		int32_t tid_state;
		const map_info_t* map_info_list;
		backtrace_frame_t* backtrace;
		size_t ignore_depth;
		@@ -96,22 +100,23 @@ static volatile struct {
		} g_unwind_signal_state;

		static void unwind_backtrace_thread_signal_handler(int n, siginfo_t* siginfo, void* sigcontext) {
		int32_t tid = android_atomic_acquire_load(&g_unwind_signal_state.tid);
		if (tid == gettid()) {
		if (!android_atomic_acquire_cas(gettid(), STATE_DUMPING, &g_unwind_signal_state.tid_state)) {
		g_unwind_signal_state.returned_frames = unwind_backtrace_signal_arch(
		siginfo, sigcontext,
		g_unwind_signal_state.map_info_list,
		g_unwind_signal_state.backtrace,
		g_unwind_signal_state.ignore_depth,
		g_unwind_signal_state.max_depth);
		android_atomic_release_store(-1, &g_unwind_signal_state.tid);
		android_atomic_release_store(STATE_DONE, &g_unwind_signal_state.tid_state);
		} else {
		ALOGV("Received spurious SIGURG on thread %d that was intended for thread %d.",
		gettid(), tid);
		gettid(), android_atomic_acquire_load(&g_unwind_signal_state.tid_state));
		}
		}
		#endif

		extern int tgkill(int tgid, int tid, int sig);

		ssize_t unwind_backtrace_thread(pid_t tid, backtrace_frame_t* backtrace,
		size_t ignore_depth, size_t max_depth) {
		if (tid == gettid()) {
		@@ -125,7 +130,7 @@ ssize_t unwind_backtrace_thread(pid_t tid, backtrace_frame_t* backtrace,
		struct sigaction oact;
		memset(&act, 0, sizeof(act));
		act.sa_sigaction = unwind_backtrace_thread_signal_handler;
		act.sa_flags = SA_RESTART \| SA_SIGINFO;
		act.sa_flags = SA_RESTART \| SA_SIGINFO \| SA_ONSTACK;
		sigemptyset(&act.sa_mask);

		pthread_mutex_lock(&g_unwind_signal_mutex);
		@@ -138,16 +143,51 @@ ssize_t unwind_backtrace_thread(pid_t tid, backtrace_frame_t* backtrace,
		g_unwind_signal_state.ignore_depth = ignore_depth;
		g_unwind_signal_state.max_depth = max_depth;
		g_unwind_signal_state.returned_frames = 0;
		android_atomic_release_store(tid, &g_unwind_signal_state.tid);
		android_atomic_release_store(tid, &g_unwind_signal_state.tid_state);

		if (kill(tid, SIGURG)) {
		// Signal the specific thread that we want to dump.
		int32_t tid_state = tid;
		if (tgkill(getpid(), tid, SIGURG)) {
		ALOGV("Failed to send SIGURG to thread %d.", tid);
		android_atomic_release_store(-1, &g_unwind_signal_state.tid);
		} else {
		while (android_atomic_acquire_load(&g_unwind_signal_state.tid) == tid) {
		ALOGV("Waiting for response from thread %d...", tid);
		// Wait for the other thread to start dumping the stack, or time out.
		int wait_millis = 250;
		for (;;) {
		tid_state = android_atomic_acquire_load(&g_unwind_signal_state.tid_state);
		if (tid_state != tid) {
		break;
		}
		if (wait_millis--) {
		ALOGV("Waiting for thread %d to start dumping the stack...", tid);
		usleep(1000);
		} else {
		ALOGV("Timed out waiting for thread %d to start dumping the stack.", tid);
		break;
		}
		}
		}

		// Try to cancel the dump if it has not started yet.
		if (tid_state == tid) {
		if (!android_atomic_acquire_cas(tid, STATE_CANCEL, &g_unwind_signal_state.tid_state)) {
		ALOGV("Canceled thread %d stack dump.", tid);
		tid_state = STATE_CANCEL;
		} else {
		tid_state = android_atomic_acquire_load(&g_unwind_signal_state.tid_state);
		}
		}

		// Wait indefinitely for the dump to finish or be canceled.
		// We cannot apply a timeout here because the other thread is accessing state that
		// is owned by this thread, such as milist. It should not take very
		// long to take the dump once started.
		while (tid_state == STATE_DUMPING) {
		ALOGV("Waiting for thread %d to finish dumping the stack...", tid);
		usleep(1000);
		tid_state = android_atomic_acquire_load(&g_unwind_signal_state.tid_state);
		}

		if (tid_state == STATE_DONE) {
		frames = g_unwind_signal_state.returned_frames;
		}