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Add test coverage for atomics (#15193)

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* Add test coverage for atomics

Signed-off-by: Elijah Shaw-Rutschman <elijahr@gmail.com>

* Fix compareExchange bugs for non-trivial objects

Bugs fixed:

1. compareExchange would not set the desired value in the success case.
2. compareExchange would not set var expected to the found value in the failure case.
3. withLock would spin forever running the unit tests. try..body..finally prevents this. Not sure why this makes a difference, since an exception wasn’t being raised, but clearing the guard in a finally block seems correct anyways.

Signed-off-by: Elijah Shaw-Rutschman <elijahr@gmail.com>
This commit is contained in:
Elijah Shaw-Rutschman
2020-08-18 11:02:10 -05:00
committed by GitHub
parent ddff13f01b
commit 8a004e2fc0
2 changed files with 616 additions and 7 deletions
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14
lib/pure/concurrency/atomics.nim
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@@ -326,8 +326,10 @@ else:
template withLock[T: not Trivial](location: var Atomic[T]; order: MemoryOrder; body: untyped): untyped =
while location.guard.testAndSet(moAcquire): discard
body
location.guard.clear(moRelease)
try:
body
finally:
location.guard.clear(moRelease)
proc load*[T: not Trivial](location: var Atomic[T]; order: MemoryOrder = moSequentiallyConsistent): T {.inline.} =
withLock(location, order):
@@ -345,16 +347,14 @@ else:
proc compareExchange*[T: not Trivial](location: var Atomic[T]; expected: var T; desired: T; success, failure: MemoryOrder): bool {.inline.} =
withLock(location, success):
if location.nonAtomicValue != expected:
expected = location.nonAtomicValue
return false
expected = desired
swap(location.nonAtomicValue, expected)
return true
proc compareExchangeWeak*[T: not Trivial](location: var Atomic[T]; expected: var T; desired: T; success, failure: MemoryOrder): bool {.inline.} =
withLock(location, success):
if location.nonAtomicValue != expected:
return false
swap(location.nonAtomicValue, expected)
return true
compareExchange(location, expected, desired, success, failure)
proc compareExchange*[T: not Trivial](location: var Atomic[T]; expected: var T; desired: T; order: MemoryOrder = moSequentiallyConsistent): bool {.inline.} =
compareExchange(location, expected, desired, order, order)