jdk-sandbox: comparison hotspot/src/os/linux/vm/os

equal deleted inserted replaced

-:f9e300086063
+:b7bcf7497f93
 static int SR_signum = SIGUSR2;
 sigset_t SR_sigset;
 /* Used to protect dlsym() calls */
 static pthread_mutex_t dl_mutex;
+// Declarations
+static void unpackTime(timespec* absTime, bool isAbsolute, jlong time);
 #ifdef JAVASE_EMBEDDED
 class MemNotifyThread: public Thread {
 friend class VMStructs;
 public:
 void* os::user_handler() {
 return CAST_FROM_FN_PTR(void*, UserHandler);
 }
+class Semaphore : public StackObj {
+public:
+Semaphore();
+~Semaphore();
+void signal();
+void wait();
+bool trywait();
+bool timedwait(unsigned int sec, int nsec);
+private:
+sem_t _semaphore;
+};
+Semaphore::Semaphore() {
+sem_init(&_semaphore, 0, 0);
+}
+Semaphore::~Semaphore() {
+sem_destroy(&_semaphore);
+}
+void Semaphore::signal() {
+sem_post(&_semaphore);
+}
+void Semaphore::wait() {
+sem_wait(&_semaphore);
+}
+bool Semaphore::trywait() {
+return sem_trywait(&_semaphore) == 0;
+}
+bool Semaphore::timedwait(unsigned int sec, int nsec) {
+struct timespec ts;
+unpackTime(&ts, false, (sec * NANOSECS_PER_SEC) + nsec);
+while (1) {
+int result = sem_timedwait(&_semaphore, &ts);
+if (result == 0) {
+return true;
+} else if (errno == EINTR) {
+continue;
+} else if (errno == ETIMEDOUT) {
+return false;
+} else {
+return false;
+}
+}
+}
 extern "C" {
 typedef void (*sa_handler_t)(int);
 typedef void (*sa_sigaction_t)(int, siginfo_t *, void *);
 }
 // a counter for each possible signal value
 static volatile jint pending_signals[NSIG+1] = { 0 };
 // Linux(POSIX) specific hand shaking semaphore.
 static sem_t sig_sem;
+static Semaphore sr_semaphore;
 void os::signal_init_pd() {
 // Initialize signal structures
 ::memset((void*)pending_signals, 0, sizeof(pending_signals));
 //
 static void resume_clear_context(OSThread *osthread) {
 osthread->set_ucontext(NULL);
 osthread->set_siginfo(NULL);
-// notify the suspend action is completed, we have now resumed
-osthread->sr.clear_suspended();
 }
 static void suspend_save_context(OSThread *osthread, siginfo_t* siginfo, ucontext_t* context) {
 osthread->set_ucontext(context);
 osthread->set_siginfo(siginfo);
 // interface point of view, but sigwait() prevents the signal hander
 // from being run. libpthread would get very confused by not having
 // its signal handlers run and prevents sigwait()'s use with the
 // mutex granting granting signal.
 //
-// Currently only ever called on the VMThread
+// Currently only ever called on the VMThread and JavaThreads (PC sampling)
 //
 static void SR_handler(int sig, siginfo_t* siginfo, ucontext_t* context) {
 // Save and restore errno to avoid confusing native code with EINTR
 // after sigsuspend.
 int old_errno = errno;
 Thread* thread = Thread::current();
 OSThread* osthread = thread->osthread();
-assert(thread->is_VM_thread(), "Must be VMThread");
+assert(thread->is_VM_thread() || thread->is_Java_thread(), "Must be VMThread or JavaThread");
-// read current suspend action
-int action = osthread->sr.suspend_action();
+os::SuspendResume::State current = osthread->sr.state();
-if (action == os::Linux::SuspendResume::SR_SUSPEND) {
+if (current == os::SuspendResume::SR_SUSPEND_REQUEST) {
 suspend_save_context(osthread, siginfo, context);
-// Notify the suspend action is about to be completed. do_suspend()
+// attempt to switch the state, we assume we had a SUSPEND_REQUEST
-// waits until SR_SUSPENDED is set and then returns. We will wait
+os::SuspendResume::State state = osthread->sr.suspended();
-// here for a resume signal and that completes the suspend-other
+if (state == os::SuspendResume::SR_SUSPENDED) {
-// action. do_suspend/do_resume is always called as a pair from
+sigset_t suspend_set;  // signals for sigsuspend()
-// the same thread - so there are no races
+// get current set of blocked signals and unblock resume signal
-// notify the caller
+pthread_sigmask(SIG_BLOCK, NULL, &suspend_set);
-osthread->sr.set_suspended();
+sigdelset(&suspend_set, SR_signum);
-sigset_t suspend_set;  // signals for sigsuspend()
+sr_semaphore.signal();
+// wait here until we are resumed
-// get current set of blocked signals and unblock resume signal
+while (1) {
-pthread_sigmask(SIG_BLOCK, NULL, &suspend_set);
+sigsuspend(&suspend_set);
-sigdelset(&suspend_set, SR_signum);
+os::SuspendResume::State result = osthread->sr.running();
-// wait here until we are resumed
+if (result == os::SuspendResume::SR_RUNNING) {
-do {
+sr_semaphore.signal();
-sigsuspend(&suspend_set);
+break;
-// ignore all returns until we get a resume signal
+}
-} while (osthread->sr.suspend_action() != os::Linux::SuspendResume::SR_CONTINUE);
+}
+} else if (state == os::SuspendResume::SR_RUNNING) {
+// request was cancelled, continue
+} else {
+ShouldNotReachHere();
+}
 resume_clear_context(osthread);
+} else if (current == os::SuspendResume::SR_RUNNING) {
+// request was cancelled, continue
+} else if (current == os::SuspendResume::SR_WAKEUP_REQUEST) {
+// ignore
 } else {
-assert(action == os::Linux::SuspendResume::SR_CONTINUE, "unexpected sr action");
+// ignore
-// nothing special to do - just leave the handler
 }
 errno = old_errno;
 }
 // Save signal flag
 os::Linux::set_our_sigflags(SR_signum, act.sa_flags);
 return 0;
 }
+static int sr_notify(OSThread* osthread) {
+int status = pthread_kill(osthread->pthread_id(), SR_signum);
+assert_status(status == 0, status, "pthread_kill");
+return status;
+}
+// "Randomly" selected value for how long we want to spin
+// before bailing out on suspending a thread, also how often
+// we send a signal to a thread we want to resume
+static const int RANDOMLY_LARGE_INTEGER = 1000000;
+static const int RANDOMLY_LARGE_INTEGER2 = 100;
 // returns true on success and false on error - really an error is fatal
 // but this seems the normal response to library errors
 static bool do_suspend(OSThread* osthread) {
+assert(osthread->sr.is_running(), "thread should be running");
+assert(!sr_semaphore.trywait(), "semaphore has invalid state");
 // mark as suspended and send signal
-osthread->sr.set_suspend_action(os::Linux::SuspendResume::SR_SUSPEND);
+if (osthread->sr.request_suspend() != os::SuspendResume::SR_SUSPEND_REQUEST) {
-int status = pthread_kill(osthread->pthread_id(), SR_signum);
+// failed to switch, state wasn't running?
-assert_status(status == 0, status, "pthread_kill");
+ShouldNotReachHere();
-// check status and wait until notified of suspension
-if (status == 0) {
-for (int i = 0; !osthread->sr.is_suspended(); i++) {
-os::yield_all(i);
-}
-osthread->sr.set_suspend_action(os::Linux::SuspendResume::SR_NONE);
-return true;
-}
-else {
-osthread->sr.set_suspend_action(os::Linux::SuspendResume::SR_NONE);
 return false;
 }
+if (sr_notify(osthread) != 0) {
+ShouldNotReachHere();
+}
+// managed to send the signal and switch to SUSPEND_REQUEST, now wait for SUSPENDED
+while (true) {
+if (sr_semaphore.timedwait(0, 2 * NANOSECS_PER_MILLISEC)) {
+break;
+} else {
+// timeout
+os::SuspendResume::State cancelled = osthread->sr.cancel_suspend();
+if (cancelled == os::SuspendResume::SR_RUNNING) {
+return false;
+} else if (cancelled == os::SuspendResume::SR_SUSPENDED) {
+// make sure that we consume the signal on the semaphore as well
+sr_semaphore.wait();
+break;
+} else {
+ShouldNotReachHere();
+return false;
+}
+}
+}
+guarantee(osthread->sr.is_suspended(), "Must be suspended");
+return true;
 }
 static void do_resume(OSThread* osthread) {
 assert(osthread->sr.is_suspended(), "thread should be suspended");
-osthread->sr.set_suspend_action(os::Linux::SuspendResume::SR_CONTINUE);
+assert(!sr_semaphore.trywait(), "invalid semaphore state");
-int status = pthread_kill(osthread->pthread_id(), SR_signum);
+if (osthread->sr.request_wakeup() != os::SuspendResume::SR_WAKEUP_REQUEST) {
-assert_status(status == 0, status, "pthread_kill");
+// failed to switch to WAKEUP_REQUEST
-// check status and wait unit notified of resumption
+ShouldNotReachHere();
-if (status == 0) {
+return;
-for (int i = 0; osthread->sr.is_suspended(); i++) {
+}
-os::yield_all(i);
-}
+while (true) {
-}
+if (sr_notify(osthread) == 0) {
-osthread->sr.set_suspend_action(os::Linux::SuspendResume::SR_NONE);
+if (sr_semaphore.timedwait(0, 2 * NANOSECS_PER_MILLISEC)) {
+if (osthread->sr.is_running()) {
+return;
+}
+}
+} else {
+ShouldNotReachHere();
+}
+}
+guarantee(osthread->sr.is_running(), "Must be running!");
 }
 ////////////////////////////////////////////////////////////////////////////////
 // interrupt support
 return false;
 }
 ///
+void os::SuspendedThreadTask::internal_do_task() {
+if (do_suspend(_thread->osthread())) {
+SuspendedThreadTaskContext context(_thread, _thread->osthread()->ucontext());
+do_task(context);
+do_resume(_thread->osthread());
+}
+}
+class PcFetcher : public os::SuspendedThreadTask {
+public:
+PcFetcher(Thread* thread) : os::SuspendedThreadTask(thread) {}
+ExtendedPC result();
+protected:
+void do_task(const os::SuspendedThreadTaskContext& context);
+private:
+ExtendedPC _epc;
+};
+ExtendedPC PcFetcher::result() {
+guarantee(is_done(), "task is not done yet.");
+return _epc;
+}
+void PcFetcher::do_task(const os::SuspendedThreadTaskContext& context) {
+Thread* thread = context.thread();
+OSThread* osthread = thread->osthread();
+if (osthread->ucontext() != NULL) {
+_epc = os::Linux::ucontext_get_pc((ucontext_t *) context.ucontext());
+} else {
+// NULL context is unexpected, double-check this is the VMThread
+guarantee(thread->is_VM_thread(), "can only be called for VMThread");
+}
+}
 // Suspends the target using the signal mechanism and then grabs the PC before
 // resuming the target. Used by the flat-profiler only
 ExtendedPC os::get_thread_pc(Thread* thread) {
 // Make sure that it is called by the watcher for the VMThread
 assert(Thread::current()->is_Watcher_thread(), "Must be watcher");
 assert(thread->is_VM_thread(), "Can only be called for VMThread");
-ExtendedPC epc;
+PcFetcher fetcher(thread);
+fetcher.run();
-OSThread* osthread = thread->osthread();
+return fetcher.result();
-if (do_suspend(osthread)) {
-if (osthread->ucontext() != NULL) {
-epc = os::Linux::ucontext_get_pc(osthread->ucontext());
-} else {
-// NULL context is unexpected, double-check this is the VMThread
-guarantee(thread->is_VM_thread(), "can only be called for VMThread");
-}
-do_resume(osthread);
-}
-// failure means pthread_kill failed for some reason - arguably this is
-// a fatal problem, but such problems are ignored elsewhere
-return epc;
 }
 int os::Linux::safe_cond_timedwait(pthread_cond_t *_cond, pthread_mutex_t *_mutex, const struct timespec *_abstime)
 {
 if (is_NPTL()) {
 if (memnotify_thread() == NULL) {
 new MemNotifyThread(fd);
 }
 }
 #endif // JAVASE_EMBEDDED

changeset 18025	b7bcf7497f93
parent 17854	d65bc1546091
child 18069	e6d4971c8650
child 22808	88bca865e247