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Fix concurrent_[bounded_]queue correctness on weak memory models #782
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Signed-off-by: Alexei Katranov <[email protected]>
alexey-katranov
commented
Feb 21, 2022
Signed-off-by: pavelkumbrasev <[email protected]>
pavelkumbrasev
approved these changes
Nov 4, 2022
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Description
The patch fixes two issues:
tail_counter
is serialization atomic that synchronizes memory related to micro_queue pages. Hence, we need to build happens-before overtail_counter
(not to read it withrelaxed
)push
andtry_pop
operations. Consider the example:The expected global order of operation is either
push->try_pop->push->try_pop
orpush->push->try_pop->try_pop
. However, the current implementation allowspush->try_pop->try_pop->push
that is not intuitively expected by humans. So, set the constraint betweenhead
andtail
loads to enforce visibility ofpush
iftry_pop
is already happened.The both issues are not reproducible on x86 and affect only systems with weak memory model, e.g. ARM.
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