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/*
* Copyright (C) 2012 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include "barrier.h"
#include "base/mutex.h"
#include "base/time_utils.h"
#include "thread.h"
namespace art {
Barrier::Barrier(int count)
: count_(count),
lock_("GC barrier lock", kThreadSuspendCountLock),
condition_("GC barrier condition", lock_) {
}
void Barrier::Pass(Thread* self) {
MutexLock mu(self, lock_);
SetCountLocked(self, count_ - 1);
}
void Barrier::Wait(Thread* self) {
Increment(self, -1);
}
void Barrier::Init(Thread* self, int count) {
MutexLock mu(self, lock_);
SetCountLocked(self, count);
}
void Barrier::Increment(Thread* self, int delta) {
MutexLock mu(self, lock_);
SetCountLocked(self, count_ + delta);
// Increment the count. If it becomes zero after the increment
// then all the threads have already passed the barrier. If
// it is non-zero then there is still one or more threads
// that have not yet called the Pass function. When the
// Pass function is called by the last thread, the count will
// be decremented to zero and a Broadcast will be made on the
// condition variable, thus waking this up.
while (count_ != 0) {
condition_.Wait(self);
}
}
bool Barrier::Increment(Thread* self, int delta, uint32_t timeout_ms) {
MutexLock mu(self, lock_);
SetCountLocked(self, count_ + delta);
bool timed_out = false;
if (count_ != 0) {
uint32_t timeout_ns = 0;
uint64_t abs_timeout = NanoTime() + MsToNs(timeout_ms);
for (;;) {
timed_out = condition_.TimedWait(self, timeout_ms, timeout_ns);
if (timed_out || count_ == 0) return timed_out;
// Compute time remaining on timeout.
uint64_t now = NanoTime();
int64_t time_left = abs_timeout - now;
if (time_left <= 0) return true;
timeout_ns = time_left % (1000*1000);
timeout_ms = time_left / (1000*1000);
}
}
return timed_out;
}
void Barrier::SetCountLocked(Thread* self, int count) {
count_ = count;
if (count == 0) {
condition_.Broadcast(self);
}
}
Barrier::~Barrier() {
CHECK_EQ(count_, 0) << "Attempted to destroy barrier with non zero count";
}
} // namespace art
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