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Fix signed-unsigned comparison warning in RunQueue

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This commit is contained in:
Eugene Zhulenev 2019-02-14 10:27:28 -08:00
parent 8c2f30c790
commit f0d42d2265
1 changed files with 41 additions and 33 deletions
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74
unsupported/Eigen/CXX11/src/ThreadPool/RunQueue.h
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@ -148,39 +148,6 @@ class RunQueue {
return n;
}
// Size returns current queue size; if NeedSizeEstimate is false, only whether
// the size is 0 is guaranteed to be correct.
// Can be called by any thread at any time.
template <bool NeedSizeEstimate>
unsigned SizeOrNotEmpty() const {
// Emptiness plays critical role in thread pool blocking. So we go to great
// effort to not produce false positives (claim non-empty queue as empty).
unsigned front = front_.load(std::memory_order_acquire);
for (;;) {
// Capture a consistent snapshot of front/tail.
unsigned back = back_.load(std::memory_order_acquire);
unsigned front1 = front_.load(std::memory_order_relaxed);
if (front != front1) {
front = front1;
std::atomic_thread_fence(std::memory_order_acquire);
continue;
}
if (NeedSizeEstimate) {
int size = (front & kMask2) - (back & kMask2);
// Fix overflow.
if (size < 0) size += 2 * kSize;
// Order of modification in push/pop is crafted to make the queue look
// larger than it is during concurrent modifications. E.g. pop can
// decrement size before the corresponding push has incremented it.
// So the computed size can be up to kSize + 1, fix it.
if (size > kSize) size = kSize;
return size;
} else {
return ((front ^ back) & kMask2);
}
}
}
// Size returns current queue size.
// Can be called by any thread at any time.
unsigned Size() const { return SizeOrNotEmpty<true>(); }
@ -220,6 +187,47 @@ class RunQueue {
std::atomic<unsigned> back_;
Elem array_[kSize];
// SizeOrNotEmpty returns current queue size; if NeedSizeEstimate is false,
// only whether the size is 0 is guaranteed to be correct.
// Can be called by any thread at any time.
template<bool NeedSizeEstimate>
unsigned SizeOrNotEmpty() const {
// Emptiness plays critical role in thread pool blocking. So we go to great
// effort to not produce false positives (claim non-empty queue as empty).
unsigned front = front_.load(std::memory_order_acquire);
for (;;) {
// Capture a consistent snapshot of front/tail.
unsigned back = back_.load(std::memory_order_acquire);
unsigned front1 = front_.load(std::memory_order_relaxed);
if (front != front1) {
front = front1;
std::atomic_thread_fence(std::memory_order_acquire);
continue;
}
if (NeedSizeEstimate) {
return CalculateSize(front, back);
} else {
// This value will be 0 if the queue is empty, and undefined otherwise.
int maybe_zero = ((front ^ back) & kMask2);
eigen_assert(maybe_zero == 0 ? CalculateSize(front, back) == 0 : true);
return maybe_zero;
}
}
}
EIGEN_ALWAYS_INLINE
unsigned CalculateSize(unsigned front, unsigned back) const {
int size = (front & kMask2) - (back & kMask2);
// Fix overflow.
if (size < 0) size += 2 * kSize;
// Order of modification in push/pop is crafted to make the queue look
// larger than it is during concurrent modifications. E.g. push can
// increment size before the corresponding pop has decremented it.
// So the computed size can be up to kSize + 1, fix it.
if (size > static_cast<int>(kSize)) size = kSize;
return size;
}
RunQueue(const RunQueue&) = delete;
void operator=(const RunQueue&) = delete;
};