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platform_system_core
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Add a logging handler on timeout. 

If the signal handler doesn't fire in the given time when trying to unwind
a thread, put on a logging handler. This prevents crashes if the signal
does eventually fire.

Bug: 23783762

(cherry picked from commit d7226f9a14)

Change-Id: Ib990a06733cc93717752ab4998f4ae26afd7e249
This commit is contained in:
Christopher Ferris 2015-09-03 11:25:55 -07:00
parent bc8c731aab
commit d9a06afb19
1 changed files with 17 additions and 1 deletions
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18
libbacktrace/BacktraceCurrent.cpp
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@ -93,6 +93,10 @@ bool BacktraceCurrent::DiscardFrame(const backtrace_frame_data_t& frame) {
static pthread_mutex_t g_sigaction_mutex = PTHREAD_MUTEX_INITIALIZER;
static void SignalLogOnly(int, siginfo_t*, void*) {
BACK_LOGE("pid %d, tid %d: Received a spurious signal %d\n", getpid(), gettid(), THREAD_SIGNAL);
}
static void SignalHandler(int, siginfo_t*, void* sigcontext) {
ThreadEntry* entry = ThreadEntry::Get(getpid(), gettid(), false);
if (!entry) {
@ -151,9 +155,21 @@ bool BacktraceCurrent::UnwindThread(size_t num_ignore_frames) {
// that we are waiting for the first Wake() call made by the thread.
bool wait_completed = entry->Wait(1);
if (!wait_completed && oldact.sa_sigaction == nullptr) {
// If the wait failed, it could be that the signal could not be delivered
// within the timeout. Add a signal handler that's simply going to log
// something so that we don't crash if the signal eventually gets
// delivered. Only do this if there isn't already an action set up.
memset(&act, 0, sizeof(act));
act.sa_sigaction = SignalLogOnly;
act.sa_flags = SA_RESTART | SA_SIGINFO | SA_ONSTACK;
sigemptyset(&act.sa_mask);
sigaction(THREAD_SIGNAL, &act, nullptr);
} else {
sigaction(THREAD_SIGNAL, &oldact, nullptr);
}
// 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 = false;