Revert^4 "Implement LockSupport.park with a futex"
This reverts commit 13f4d9631db981ae5008073db4df9c6a934fc9f3.
Reason for revert: Fixing ThreadStress timeouts.
Change-Id: I9f8c3f56eccfadc3751049731e8d427873cc7841
diff --git a/runtime/thread.cc b/runtime/thread.cc
index dda3b82..66e852a 100644
--- a/runtime/thread.cc
+++ b/runtime/thread.cc
@@ -44,6 +44,7 @@
#include "arch/context.h"
#include "art_field-inl.h"
#include "art_method-inl.h"
+#include "base/atomic.h"
#include "base/bit_utils.h"
#include "base/casts.h"
#include "base/file_utils.h"
@@ -285,6 +286,116 @@
<< "No deoptimization context for thread " << *this;
}
+enum {
+ kPermitAvailable = 0, // Incrementing consumes the permit
+ kNoPermit = 1, // Incrementing marks as waiter waiting
+ kNoPermitWaiterWaiting = 2
+};
+
+void Thread::Park(bool is_absolute, int64_t time) {
+ DCHECK(this == Thread::Current());
+#if ART_USE_FUTEXES
+ // Consume the permit, or mark as waiting. This cannot cause park_state to go
+ // outside of its valid range (0, 1, 2), because in all cases where 2 is
+ // assigned it is set back to 1 before returning, and this method cannot run
+ // concurrently with itself since it operates on the current thread.
+ int old_state = tls32_.park_state_.fetch_add(1, std::memory_order_relaxed);
+ if (old_state == kNoPermit) {
+ // no permit was available. block thread until later.
+ // TODO: Call to signal jvmti here
+ int result = 0;
+ if (!is_absolute && time == 0) {
+ // Thread.getState() is documented to return waiting for untimed parks.
+ ScopedThreadSuspension sts(this, ThreadState::kWaiting);
+ DCHECK_EQ(NumberOfHeldMutexes(), 0u);
+ result = futex(tls32_.park_state_.Address(),
+ FUTEX_WAIT_PRIVATE,
+ /* sleep if val = */ kNoPermitWaiterWaiting,
+ /* timeout */ nullptr,
+ nullptr,
+ 0);
+ } else if (time > 0) {
+ // Only actually suspend and futex_wait if we're going to wait for some
+ // positive amount of time - the kernel will reject negative times with
+ // EINVAL, and a zero time will just noop.
+
+ // Thread.getState() is documented to return timed wait for timed parks.
+ ScopedThreadSuspension sts(this, ThreadState::kTimedWaiting);
+ DCHECK_EQ(NumberOfHeldMutexes(), 0u);
+ timespec timespec;
+ if (is_absolute) {
+ // Time is millis when scheduled for an absolute time
+ timespec.tv_nsec = (time % 1000) * 1000000;
+ timespec.tv_sec = time / 1000;
+ // This odd looking pattern is recommended by futex documentation to
+ // wait until an absolute deadline, with otherwise identical behavior to
+ // FUTEX_WAIT_PRIVATE. This also allows parkUntil() to return at the
+ // correct time when the system clock changes.
+ result = futex(tls32_.park_state_.Address(),
+ FUTEX_WAIT_BITSET_PRIVATE | FUTEX_CLOCK_REALTIME,
+ /* sleep if val = */ kNoPermitWaiterWaiting,
+ ×pec,
+ nullptr,
+ FUTEX_BITSET_MATCH_ANY);
+ } else {
+ // Time is nanos when scheduled for a relative time
+ timespec.tv_sec = time / 1000000000;
+ timespec.tv_nsec = time % 1000000000;
+ result = futex(tls32_.park_state_.Address(),
+ FUTEX_WAIT_PRIVATE,
+ /* sleep if val = */ kNoPermitWaiterWaiting,
+ ×pec,
+ nullptr,
+ 0);
+ }
+ }
+ if (result == -1) {
+ switch (errno) {
+ case EAGAIN:
+ case ETIMEDOUT:
+ case EINTR: break; // park() is allowed to spuriously return
+ default: PLOG(FATAL) << "Failed to park";
+ }
+ }
+ // Mark as no longer waiting, and consume permit if there is one.
+ tls32_.park_state_.store(kNoPermit, std::memory_order_relaxed);
+ // TODO: Call to signal jvmti here
+ } else {
+ // the fetch_add has consumed the permit. immediately return.
+ DCHECK_EQ(old_state, kPermitAvailable);
+ }
+#else
+ #pragma clang diagnostic push
+ #pragma clang diagnostic warning "-W#warnings"
+ #warning "LockSupport.park/unpark implemented as noops without FUTEX support."
+ #pragma clang diagnostic pop
+ UNUSED(is_absolute, time);
+ UNIMPLEMENTED(WARNING);
+ sched_yield();
+#endif
+}
+
+void Thread::Unpark() {
+#if ART_USE_FUTEXES
+ // Set permit available; will be consumed either by fetch_add (when the thread
+ // tries to park) or store (when the parked thread is woken up)
+ if (tls32_.park_state_.exchange(kPermitAvailable, std::memory_order_relaxed)
+ == kNoPermitWaiterWaiting) {
+ int result = futex(tls32_.park_state_.Address(),
+ FUTEX_WAKE_PRIVATE,
+ /* number of waiters = */ 1,
+ nullptr,
+ nullptr,
+ 0);
+ if (result == -1) {
+ PLOG(FATAL) << "Failed to unpark";
+ }
+ }
+#else
+ UNIMPLEMENTED(WARNING);
+#endif
+}
+
void Thread::PushStackedShadowFrame(ShadowFrame* sf, StackedShadowFrameType type) {
StackedShadowFrameRecord* record = new StackedShadowFrameRecord(
sf, type, tlsPtr_.stacked_shadow_frame_record);
@@ -489,6 +600,22 @@
runtime->GetRuntimeCallbacks()->ThreadStart(self);
+ // Unpark ourselves if the java peer was unparked before it started (see
+ // b/28845097#comment49 for more information)
+
+ ArtField* unparkedField = jni::DecodeArtField(
+ WellKnownClasses::java_lang_Thread_unparkedBeforeStart);
+ bool should_unpark = false;
+ {
+ // Hold the lock here, so that if another thread calls unpark before the thread starts
+ // we don't observe the unparkedBeforeStart field before the unparker writes to it,
+ // which could cause a lost unpark.
+ art::MutexLock mu(soa.Self(), *art::Locks::thread_list_lock_);
+ should_unpark = unparkedField->GetBoolean(self->tlsPtr_.opeer) == JNI_TRUE;
+ }
+ if (should_unpark) {
+ self->Unpark();
+ }
// Invoke the 'run' method of our java.lang.Thread.
ObjPtr<mirror::Object> receiver = self->tlsPtr_.opeer;
jmethodID mid = WellKnownClasses::java_lang_Thread_run;
@@ -2133,6 +2260,9 @@
tls32_.state_and_flags.as_struct.flags = 0;
tls32_.state_and_flags.as_struct.state = kNative;
tls32_.interrupted.store(false, std::memory_order_relaxed);
+ // Initialize with no permit; if the java Thread was unparked before being
+ // started, it will unpark itself before calling into java code.
+ tls32_.park_state_.store(kNoPermit, std::memory_order_relaxed);
memset(&tlsPtr_.held_mutexes[0], 0, sizeof(tlsPtr_.held_mutexes));
std::fill(tlsPtr_.rosalloc_runs,
tlsPtr_.rosalloc_runs + kNumRosAllocThreadLocalSizeBracketsInThread,
@@ -2449,12 +2579,15 @@
}
void Thread::Interrupt(Thread* self) {
- MutexLock mu(self, *wait_mutex_);
- if (tls32_.interrupted.load(std::memory_order_seq_cst)) {
- return;
+ {
+ MutexLock mu(self, *wait_mutex_);
+ if (tls32_.interrupted.load(std::memory_order_seq_cst)) {
+ return;
+ }
+ tls32_.interrupted.store(true, std::memory_order_seq_cst);
+ NotifyLocked(self);
}
- tls32_.interrupted.store(true, std::memory_order_seq_cst);
- NotifyLocked(self);
+ Unpark();
}
void Thread::Notify() {