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Revert "fix a race in jobsystem"

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This reverts commit 2feb0ad325.
This commit is contained in:
Benjamin Doherty
2021-09-24 11:24:44 -07:00
parent 1a3cee9da9
commit 1f403fdae0
2 changed files with 17 additions and 39 deletions
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41
libs/utils/include/utils/JobSystem.h
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@@ -354,56 +354,19 @@ private:
assert(job);
size_t index = job - mJobStorageBase;
assert(index >= 0 && index < MAX_JOB_COUNT);
// put the job into the queue first
workQueue.push(uint16_t(index + 1));
// then increase our active job count
uint32_t oldActiveJobs = mActiveJobs.fetch_add(1, std::memory_order_relaxed);
// but it's possible that the job has already been picked-up, so oldActiveJobs could be
// negative for instance. We signal only if that's not the case.
if (oldActiveJobs >= 0) {
wakeOne(); // wake-up a thread if needed...
}
}
Job* pop(WorkQueue& workQueue) noexcept {
// decrement mActiveJobs first, this is to ensure that if there is only a single job left
// (and we're about to pick it up), other threads don't loop trying to do the same.
mActiveJobs.fetch_sub(1, std::memory_order_relaxed);
size_t index = workQueue.pop();
assert(index <= MAX_JOB_COUNT);
Job* job = !index ? nullptr : &mJobStorageBase[index - 1];
// if our guess was wrong, i.e. we couldn't pick-up a job (b/c our queue was empty), we
// need to correct mActiveJobs.
if (!job) {
if (mActiveJobs.fetch_add(1, std::memory_order_relaxed) >= 0) {
// and if there are some active jobs, then we need to wake someone up. We know it
// can't be us, because we failed taking a job and we know another thread can't
// have added one in our queue.
wakeOne();
}
}
return job;
return !index ? nullptr : &mJobStorageBase[index - 1];
}
Job* steal(WorkQueue& workQueue) noexcept {
// decrement mActiveJobs first, this is to ensure that if there is only a single job left
// (and we're about to pick it up), other threads don't loop trying to do the same.
mActiveJobs.fetch_sub(1, std::memory_order_relaxed);
size_t index = workQueue.steal();
assert(index <= MAX_JOB_COUNT);
Job* job = !index ? nullptr : &mJobStorageBase[index - 1];
// if we failed taking a job, we need to correct mActiveJobs
if (!job) {
mActiveJobs.fetch_add(1, std::memory_order_relaxed);
// we don't need to signal here, because we're going to loop back into this thread to
// try again.
}
return job;
return !index ? nullptr : &mJobStorageBase[index - 1];
}
void wait(std::unique_lock<Mutex>& lock, Job* job = nullptr) noexcept;