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// Copyright 2018 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "watchdog.h"
#include <assert.h>
#include <errno.h>
#include <inttypes.h>
#include <limits.h>
#include <pthread.h>
#include <string.h>
#include <time.h>
#include <unistd.h>
#include <unittest/unittest.h>
#include <zircon/compiler.h>
constexpr int WATCHDOG_ERRCODE = 5;
constexpr uint64_t NANOSECONDS_PER_SECOND = 1000 * 1000 * 1000;
// The watchdog thread wakes up after this many seconds to check whether
// a test has timed out. The lower the number this is the more accurate
// the watchdog is with regard to the specified timeout. But there's
// no point in running too frequently. The wait mechanism we use is
// interruptible, so this value can be high and there's no worries of waiting
// for the watchdog to terminate. The watchdog works this way so that we
// can have one watchdog thread that is continuously running instead of
// starting a new watchdog thread for each test. Another goal is to not
// require any synchronization between the watchdog thread and the test.
// E.g., We don't want to have to wait for the watchdog to acknowledge that
// a test is starting and stopping. Instead we just let it run at its own pace.
// Tests often complete in milliseconds, far lower than our "tick".
constexpr int WATCHDOG_TICK_SECONDS = 1;
// Value stored in |active_timeout_seconds| to indicate test is not running.
// This can be overridden by the user by setting env var WATCHDOG_ENV_NAME.
static int base_timeout_seconds = DEFAULT_BASE_TIMEOUT_SECONDS;
static pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;
// Cond used to wait on the watchdog thread starting.
static pthread_cond_t init_cond = PTHREAD_COND_INITIALIZER;
static bool init_done = false;
// The name of the current test.
// Used to report which test timed out.
static const char* test_name; //TA_GUARDED(mutex)
// The current timeout in effect.
// When tests aren't running we set this to INT_MAX.
static int active_timeout_seconds = WATCHDOG_TIMEOUT_NOT_RUNNING; //TA_GUARDED(mutex)
// The time when the test was started.
// This is the result of clock_gettime converted to nanoseconds.
static uint64_t test_start_time; //TA_GUARDED(mutex)
// True if tests are running.
// Set by watchdog initialize(), reset by watchdog_terminate().
static bool tests_running; //TA_GUARDED(mutex)
static pthread_t watchdog_thread;
// This library is used for both the host and target.
// For portability concerns we use pthread_cond_timedwait to get a
// cancelable wait.
static pthread_cond_t cond = PTHREAD_COND_INITIALIZER;
static uint64_t timespec_to_nanoseconds(const struct timespec* ts) {
return (ts->tv_sec * NANOSECONDS_PER_SECOND) + ts->tv_nsec;
* Set the base timeout.
* |timeout| must be >= 0.
* A value of zero disables the timeout.
* The timeout must be set before calling watchdog_initialize(), and must
* not be changed until after watchdog_terminate() is called.
void watchdog_set_base_timeout(int seconds) {
assert(seconds >= 0);
base_timeout_seconds = seconds;
static int test_timeout_for_type(test_type_t type) {
int factor;
switch (type) {
int64_t timeout = base_timeout_seconds * factor;
if (timeout > INT_MAX)
timeout = INT_MAX;
return static_cast<int>(timeout);
* Return true if watchdog support is enabled for this test run.
bool watchdog_is_enabled() {
return base_timeout_seconds > 0;
static __NO_RETURN void watchdog_signal_timeout(const char* name) {
unittest_printf_critical("\n\n*** WATCHDOG TIMER FIRED, test: %s ***\n", name);
static void* watchdog_thread_func(void* arg) {
init_done = true;
for (;;) {
// Has watchdog_terminate() been called?
// Test this here, before calling pthread_cond_timedwait(), so that
// we catch the case of all tests completing and watchdog_terminate
// being called before we get started. Otherwise we'll wait one tick
// before we notice this.
if (!tests_running) {
// Use REALTIME because that's the default clock for conds and
// OSX doesn't include the pthread APIs for changing it.
struct timespec delay;
clock_gettime(CLOCK_REALTIME, &delay);
delay.tv_sec += WATCHDOG_TICK_SECONDS;
// If compiled with #define NDEBUG the assert essentially goes away.
// Thus we need to protect |result| with __UNUSED lest the compiler
// complain and fail the build.
auto result __UNUSED = pthread_cond_timedwait(&cond, &mutex, &delay);
// We can time-out just as watchdog_terminate() is called, and
// thus we can't make any assumptions based on |result|.
assert(result == 0 || result == ETIMEDOUT);
struct timespec now;
clock_gettime(CLOCK_MONOTONIC, &now);
uint64_t now_nanos = timespec_to_nanoseconds(&now);
assert (now_nanos >= test_start_time);
uint64_t elapsed_nanos = now_nanos - test_start_time;
// Note: We skip worrying about handling the (rare) case where the
// test completes but before it can notify us we wake and see that
// the timeout has been reached.
uint64_t timeout_nanos = active_timeout_seconds * NANOSECONDS_PER_SECOND;
if (elapsed_nanos >= timeout_nanos) {
return nullptr;
* Start the watchdog thread.
* The thread begins in an idle state, waiting for watchdog_start().
* This must only be called once.
void watchdog_initialize() {
if (watchdog_is_enabled()) {
tests_running = true;
// We don't want the watchdog thread to commit pages while tests are running as that
// muddies page usage stats. To avoid that, wait for the thread to start before running
// the tests. Currently, the watchdog thread always uses the unsafe stacks during
// initialization; if that changes, then we'll need to explicitly write to it.
int res = pthread_create(&watchdog_thread, nullptr, &watchdog_thread_func, NULL);
if (res == 0) {
while (!init_done) {
pthread_cond_wait(&init_cond, &mutex);
if (res != 0) {
unittest_printf_critical("ERROR STARTING WATCHDOG THREAD: %d(%s)\n", res, strerror(res));
* Turn on the watchdog timer for test |name|.
* Storage for |name| must survive the duration of the test.
* If the timer goes off the process terminates.
* This must be called at the start of a test.
void watchdog_start(test_type_t type, const char* name) {
if (watchdog_is_enabled()) {
test_name = name;
active_timeout_seconds = test_timeout_for_type(type);
struct timespec now;
clock_gettime(CLOCK_MONOTONIC, &now);
test_start_time = timespec_to_nanoseconds(&now);
* Call this to turn off the watchdog timer.
* Yeah, there's a "race" if a test finishes right when we're called.
* We don't worry about this small window given the amount of time we wait.
* This must be called after watchdog_start().
void watchdog_cancel() {
if (watchdog_is_enabled()) {
active_timeout_seconds = WATCHDOG_TIMEOUT_NOT_RUNNING;
test_name = nullptr;
* Terminate the watchdog thread.
* This must be called after all tests complete.
void watchdog_terminate() {
// All tests must have completed.
assert(active_timeout_seconds == WATCHDOG_TIMEOUT_NOT_RUNNING);
if (watchdog_is_enabled()) {
tests_running = false;
__UNUSED int res = pthread_cond_signal(&cond);
assert(res == 0);
res = pthread_join(watchdog_thread, NULL);
assert(res == 0);