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| author | Ben Gamari <ben@smart-cactus.org> | 2020-10-22 12:02:58 -0400 |
|---|---|---|
| committer | Ben Gamari <ben@smart-cactus.org> | 2020-10-24 21:00:40 -0400 |
| commit | 3416244b736b386f0bbf8369083f90110cd524a2 (patch) | |
| tree | 2fba1c6e5ee086350dab52efd083c11e9ae3c96e /rts/Schedule.c | |
| parent | dd175a926c0e9654cd6ac8d9d26b183540c87331 (diff) | |
| download | haskell-3416244b736b386f0bbf8369083f90110cd524a2.tar.gz | |
Capabiliity: Properly fix data race on n_returning_tasks
There is a real data race but can be made safe by using proper atomic
(but relaxed) accesses.
Diffstat (limited to 'rts/Schedule.c')
| -rw-r--r-- | rts/Schedule.c | 9 |
1 files changed, 7 insertions, 2 deletions
diff --git a/rts/Schedule.c b/rts/Schedule.c index 20f661ac97..52d89a08fb 100644 --- a/rts/Schedule.c +++ b/rts/Schedule.c @@ -654,9 +654,14 @@ shouldYieldCapability (Capability *cap, Task *task, bool didGcLast) // Capability keeps forcing a GC and the other Capabilities make no // progress at all. + // Note [Data race in shouldYieldCapability] + // ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ // We would usually need to hold cap->lock to look at n_returning_tasks but - // we don't here since this is just an approximate predicate. - TSAN_ANNOTATE_BENIGN_RACE(&cap->n_returning_tasks, "shouldYieldCapability"); + // we don't here since this is just an approximate predicate. We + // consequently need to use atomic accesses whenever touching + // n_returning_tasks. However, since this is an approximate predicate we can + // use a RELAXED ordering. + return ((RELAXED_LOAD(&pending_sync) && !didGcLast) || RELAXED_LOAD(&cap->n_returning_tasks) != 0 || (!emptyRunQueue(cap) && (task->incall->tso == NULL |