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Differential D38611

aio: Fix more synchronization issues in aio_biowakeup.
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Authored by jhb on Feb 15 2023, 7:02 PM.
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markj
mjg
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rGfe6953f70fab: aio: Fix more synchronization issues in aio_biowakeup.
rG98844e99d40a: aio: Fix more synchronization issues in aio_biowakeup.
Summary
  • Use atomic_store to set job->error. atomic_set does an or operation, not assignment.
  • Use refcount_* to manage job->nbio.

    This ensures proper memory barriers are present so that the last bio won't see a possibly stale value of job->error.
  • Don't re-read job->error after reading it via atomic_load.

Reported by: markj (1)

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Event Timeline

jhb created this revision.Feb 15 2023, 7:02 PM
Herald added a subscriber: imp. · View Herald TranscriptFeb 15 2023, 7:02 PM
jhb requested review of this revision.Feb 15 2023, 7:02 PM
Harbormaster completed remote builds in B49809: Diff 117316.Feb 15 2023, 7:03 PM
mjg accepted this revision.Feb 15 2023, 7:06 PM

hrmpf

so turns out atomic_set *is* like atomic_store on linux....

mumbling ensues

that is just a side note though

another one is that the volatile u_int stuff for refcounts needs to die, but again not a blocker

This revision is now accepted and ready to land.Feb 15 2023, 7:06 PM
markj accepted this revision.Feb 15 2023, 7:11 PM
Closed by commit rG98844e99d40a: aio: Fix more synchronization issues in aio_biowakeup. (authored by jhb). · Explain WhyFeb 15 2023, 9:33 PM
This revision was automatically updated to reflect the committed changes.
jhb added a commit: rG98844e99d40a: aio: Fix more synchronization issues in aio_biowakeup..
jhb added a commit: rGfe6953f70fab: aio: Fix more synchronization issues in aio_biowakeup..Sep 6 2023, 9:57 PM

Revision Contents
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sys/
kern/
11 lines
sys/
2 lines

Diff 117334

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sys/kern/vfs_aio.c

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sys/sys/aio.h

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