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Merge "Minor robustness tweaks."

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This commit is contained in:
Jeff Brown 2011-11-21 13:13:12 -08:00 • committed by Android (Google) Code Review
commit de8b136d5a
1 changed files with 52 additions and 12 deletions
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64
libcorkscrew/backtrace.c
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@ -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);
usleep(1000);
// 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;
}