Merge "Rewrite unwind thread handling." (3a088524) · Commits · e / os / android_system_core

include/backtrace/Backtrace.h

+2 −1

Original line number	Diff line number	Diff line
		@@ -19,6 +19,7 @@

		#include <inttypes.h>
		#include <stdint.h>
		#include <ucontext.h>

		#include <string>
		#include <vector>
		@@ -64,7 +65,7 @@ public:
		virtual ~Backtrace();

		// Get the current stack trace and store in the backtrace_ structure.
		virtual bool Unwind(size_t num_ignore_frames);
		virtual bool Unwind(size_t num_ignore_frames, ucontext_t* context = NULL);

		// Get the function name and offset into the function given the pc.
		// If the string is empty, then no valid function name was found.

libbacktrace/Android.mk

+3 −0

Original line number	Diff line number	Diff line
		@@ -116,6 +116,9 @@ backtrace_test_shared_libraries := \
		backtrace_test_shared_libraries_target := \
		libcutils \

		backtrace_test_static_libraries_host := \
		libcutils \

		module := backtrace_test
		module_tag := debug
		build_type := target

libbacktrace/BacktraceImpl.cpp

+2 −2

Original line number	Diff line number	Diff line
		@@ -55,8 +55,8 @@ Backtrace::~Backtrace() {
		}
		}

		bool Backtrace::Unwind(size_t num_ignore_frames) {
		return impl_->Unwind(num_ignore_frames);
		bool Backtrace::Unwind(size_t num_ignore_frames, ucontext_t* ucontext) {
		return impl_->Unwind(num_ignore_frames, ucontext);
		}

		extern "C" char* __cxa_demangle(const char* mangled, char* buf, size_t* len,

libbacktrace/BacktraceImpl.h

+2 −1

Original line number	Diff line number	Diff line
		@@ -21,12 +21,13 @@
		#include <backtrace/BacktraceMap.h>

		#include <sys/types.h>
		#include <ucontext.h>

		class BacktraceImpl {
		public:
		virtual ~BacktraceImpl() { }

		virtual bool Unwind(size_t num_ignore_frames) = 0;
		virtual bool Unwind(size_t num_ignore_frames, ucontext_t* ucontext) = 0;

		// The name returned is not demangled, Backtrace::GetFunctionName()
		// takes care of demangling the name.

libbacktrace/BacktraceThread.cpp

+129 −141

Original line number	Diff line number	Diff line
		@@ -16,10 +16,15 @@

		#include <errno.h>
		#include <inttypes.h>
		#include <limits.h>
		#include <linux/futex.h>
		#include <pthread.h>
		#include <signal.h>
		#include <string.h>
		#include <sys/syscall.h>
		#include <sys/time.h>
		#include <sys/types.h>
		#include <ucontext.h>

		#include <cutils/atomic.h>

		@@ -27,190 +32,173 @@
		#include "BacktraceThread.h"
		#include "thread_utils.h"

		static inline int futex(volatile int* uaddr, int op, int val, const struct timespec* ts, volatile int* uaddr2, int val3) {
		return syscall(__NR_futex, uaddr, op, val, ts, uaddr2, val3);
		}

		//-------------------------------------------------------------------------
		// ThreadEntry implementation.
		//-------------------------------------------------------------------------
		static ThreadEntry* g_list = NULL;
		static pthread_mutex_t g_entry_mutex = PTHREAD_MUTEX_INITIALIZER;
		static pthread_mutex_t g_sigaction_mutex = PTHREAD_MUTEX_INITIALIZER;
		ThreadEntry* ThreadEntry::list_ = NULL;
		pthread_mutex_t ThreadEntry::list_mutex_ = PTHREAD_MUTEX_INITIALIZER;

		ThreadEntry::ThreadEntry(
		BacktraceThreadInterface* intf, pid_t pid, pid_t tid, size_t num_ignore_frames)
		: thread_intf(intf), pid(pid), tid(tid), next(NULL), prev(NULL),
		state(STATE_WAITING), num_ignore_frames(num_ignore_frames) {
		// Assumes that ThreadEntry::list_mutex_ has already been locked before
		// creating a ThreadEntry object.
		ThreadEntry::ThreadEntry(pid_t pid, pid_t tid)
		: pid_(pid), tid_(tid), futex_(0), ref_count_(1), mutex_(PTHREAD_MUTEX_INITIALIZER), next_(ThreadEntry::list_), prev_(NULL) {
		// Add ourselves to the list.
		if (ThreadEntry::list_) {
		ThreadEntry::list_->prev_ = this;
		}
		ThreadEntry::list_ = this;
		}

		ThreadEntry::~ThreadEntry() {
		pthread_mutex_lock(&g_entry_mutex);
		if (g_list == this) {
		g_list = next;
		} else {
		if (next) {
		next->prev = prev;
		ThreadEntry* ThreadEntry::Get(pid_t pid, pid_t tid, bool create) {
		pthread_mutex_lock(&ThreadEntry::list_mutex_);
		ThreadEntry* entry = list_;
		while (entry != NULL) {
		if (entry->Match(pid, tid)) {
		break;
		}
		prev->next = next;
		entry = entry->next_;
		}
		pthread_mutex_unlock(&g_entry_mutex);

		next = NULL;
		prev = NULL;
		if (!entry) {
		if (create) {
		entry = new ThreadEntry(pid, tid);
		}
		} else {
		entry->ref_count_++;
		}
		pthread_mutex_unlock(&ThreadEntry::list_mutex_);

		ThreadEntry* ThreadEntry::AddThreadToUnwind(
		BacktraceThreadInterface* intf, pid_t pid, pid_t tid, size_t num_ignore_frames) {
		ThreadEntry* entry = new ThreadEntry(intf, pid, tid, num_ignore_frames);
		return entry;
		}

		pthread_mutex_lock(&g_entry_mutex);
		ThreadEntry* cur_entry = g_list;
		while (cur_entry != NULL) {
		if (cur_entry->Match(pid, tid)) {
		// There is already an entry for this pid/tid, this is bad.
		BACK_LOGW("Entry for pid %d tid %d already exists.", pid, tid);
		void ThreadEntry::Remove(ThreadEntry* entry) {
		pthread_mutex_unlock(&entry->mutex_);

		pthread_mutex_unlock(&g_entry_mutex);
		return NULL;
		pthread_mutex_lock(&ThreadEntry::list_mutex_);
		if (--entry->ref_count_ == 0) {
		delete entry;
		}
		cur_entry = cur_entry->next;
		pthread_mutex_unlock(&ThreadEntry::list_mutex_);
		}

		// Add the entry to the list.
		entry->next = g_list;
		if (g_list) {
		g_list->prev = entry;
		// Assumes that ThreadEntry::list_mutex_ has already been locked before
		// deleting a ThreadEntry object.
		ThreadEntry::~ThreadEntry() {
		if (list_ == this) {
		list_ = next_;
		} else {
		if (next_) {
		next_->prev_ = prev_;
		}
		g_list = entry;
		pthread_mutex_unlock(&g_entry_mutex);

		return entry;
		prev_->next_ = next_;
		}

		//-------------------------------------------------------------------------
		// BacktraceThread functions.
		//-------------------------------------------------------------------------
		static void SignalHandler(int n __attribute__((unused)), siginfo_t* siginfo,
		void* sigcontext) {
		if (pthread_mutex_lock(&g_entry_mutex) == 0) {
		pid_t pid = getpid();
		pid_t tid = gettid();
		ThreadEntry* cur_entry = g_list;
		while (cur_entry) {
		if (cur_entry->Match(pid, tid)) {
		break;
		}
		cur_entry = cur_entry->next;
		}
		pthread_mutex_unlock(&g_entry_mutex);
		if (!cur_entry) {
		BACK_LOGW("Unable to find pid %d tid %d information", pid, tid);
		return;
		next_ = NULL;
		prev_ = NULL;
		}

		if (android_atomic_acquire_cas(STATE_WAITING, STATE_DUMPING, &cur_entry->state) == 0) {
		cur_entry->thread_intf->ThreadUnwind(siginfo, sigcontext,
		cur_entry->num_ignore_frames);
		}
		android_atomic_release_store(STATE_DONE, &cur_entry->state);
		void ThreadEntry::Wait(int value) {
		timespec ts;
		ts.tv_sec = 10;
		ts.tv_nsec = 0;
		errno = 0;
		futex(&futex_, FUTEX_WAIT, value, &ts, NULL, 0);
		if (errno != 0 && errno != EWOULDBLOCK) {
		BACK_LOGW("futex wait failed, futex = %d: %s", futex_, strerror(errno));
		}
		}

		BacktraceThread::BacktraceThread(
		BacktraceImpl* impl, BacktraceThreadInterface* thread_intf, pid_t tid,
		BacktraceMap* map)
		: BacktraceCurrent(impl, map), thread_intf_(thread_intf) {
		tid_ = tid;
		void ThreadEntry::Wake() {
		futex_++;
		futex(&futex_, FUTEX_WAKE, INT_MAX, NULL, NULL, 0);
		}

		BacktraceThread::~BacktraceThread() {
		//-------------------------------------------------------------------------
		// BacktraceThread functions.
		//-------------------------------------------------------------------------
		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());
		return;
		}

		void BacktraceThread::FinishUnwind() {
		for (std::vector<backtrace_frame_data_t>::iterator it = frames_.begin();
		it != frames_.end(); ++it) {
		it->map = FindMap(it->pc);
		entry->CopyUcontext(reinterpret_cast<ucontext_t*>(sigcontext));

		it->func_offset = 0;
		it->func_name = GetFunctionName(it->pc, &it->func_offset);
		}
		}
		// Indicate the ucontext is now valid.
		entry->Wake();

		bool BacktraceThread::TriggerUnwindOnThread(ThreadEntry* entry) {
		entry->state = STATE_WAITING;
		// Pause the thread until the unwind is complete. This avoids having
		// the thread run ahead causing problems.
		entry->Wait(1);

		if (tgkill(Pid(), Tid(), THREAD_SIGNAL) != 0) {
		BACK_LOGW("tgkill failed %s", strerror(errno));
		return false;
		ThreadEntry::Remove(entry);
		}

		// Allow up to ten seconds for the dump to start.
		int wait_millis = 10000;
		int32_t state;
		while (true) {
		state = android_atomic_acquire_load(&entry->state);
		if (state != STATE_WAITING) {
		break;
		}
		if (wait_millis--) {
		usleep(1000);
		} else {
		break;
		}
		BacktraceThread::BacktraceThread(BacktraceImpl* impl, pid_t tid, BacktraceMap* map)
		: BacktraceCurrent(impl, map) {
		tid_ = tid;
		}

		bool cancelled = false;
		if (state == STATE_WAITING) {
		if (android_atomic_acquire_cas(state, STATE_CANCEL, &entry->state) == 0) {
		BACK_LOGW("Cancelled dump of thread %d", entry->tid);
		state = STATE_CANCEL;
		cancelled = true;
		} else {
		state = android_atomic_acquire_load(&entry->state);
		}
		BacktraceThread::~BacktraceThread() {
		}

		// Wait for at most ten seconds for the cancel or dump to finish.
		wait_millis = 10000;
		while (android_atomic_acquire_load(&entry->state) != STATE_DONE) {
		if (wait_millis--) {
		usleep(1000);
		} else {
		BACK_LOGW("Didn't finish thread unwind in 60 seconds.");
		break;
		}
		}
		return !cancelled;
		bool BacktraceThread::Unwind(size_t num_ignore_frames, ucontext_t* ucontext) {
		if (ucontext) {
		// Unwind using an already existing ucontext.
		return impl_->Unwind(num_ignore_frames, ucontext);
		}

		bool BacktraceThread::Unwind(size_t num_ignore_frames) {
		ThreadEntry* entry = ThreadEntry::AddThreadToUnwind(
		thread_intf_, Pid(), Tid(), num_ignore_frames);
		if (!entry) {
		// Prevent multiple threads trying to set the trigger action on different
		// threads at the same time.
		if (pthread_mutex_lock(&g_sigaction_mutex) < 0) {
		BACK_LOGW("sigaction failed: %s", strerror(errno));
		return false;
		}

		// Prevent multiple threads trying to set the trigger action on different
		// threads at the same time.
		bool retval = false;
		if (pthread_mutex_lock(&g_sigaction_mutex) == 0) {
		ThreadEntry* entry = ThreadEntry::Get(Pid(), Tid());
		entry->Lock();

		struct sigaction act, oldact;
		memset(&act, 0, sizeof(act));
		act.sa_sigaction = SignalHandler;
		act.sa_flags = SA_RESTART \| SA_SIGINFO \| SA_ONSTACK;
		sigemptyset(&act.sa_mask);
		if (sigaction(THREAD_SIGNAL, &act, &oldact) == 0) {
		retval = TriggerUnwindOnThread(entry);
		sigaction(THREAD_SIGNAL, &oldact, NULL);
		} else {
		if (sigaction(THREAD_SIGNAL, &act, &oldact) != 0) {
		BACK_LOGW("sigaction failed %s", strerror(errno));
		}
		entry->Unlock();
		ThreadEntry::Remove(entry);
		pthread_mutex_unlock(&g_sigaction_mutex);
		} else {
		BACK_LOGW("unable to acquire sigaction mutex.");
		return false;
		}

		if (retval) {
		FinishUnwind();
		if (tgkill(Pid(), Tid(), THREAD_SIGNAL) != 0) {
		BACK_LOGW("tgkill %d failed: %s", Tid(), strerror(errno));
		sigaction(THREAD_SIGNAL, &oldact, NULL);
		entry->Unlock();
		ThreadEntry::Remove(entry);
		pthread_mutex_unlock(&g_sigaction_mutex);
		return false;
		}
		delete entry;

		return retval;
		// Wait for the thread to get the ucontext.
		entry->Wait(0);

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

		bool unwind_done = impl_->Unwind(num_ignore_frames, entry->GetUcontext());

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

		return unwind_done;
		}