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From: "michael.bacarella at gmail dot com" <sourceware-bugzilla@sourceware.org>
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Subject: [Bug nptl/25847] pthread_cond_signal failed to wake up
 pthread_cond_wait due to a bug in undoing stealing
Date: Fri, 24 Sep 2021 00:58:17 +0000
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https://sourceware.org/bugzilla/show_bug.cgi?id=3D25847

--- Comment #44 from Michael Bacarella <michael.bacarella at gmail dot com>=
 ---
> The patch from comment 2 (the same one in Ubuntu 18.04) does not solve th=
e issue.
> I can still reproduce the issue after applying it.
> I've been studying and evaluating the patches from comments 13 and 38, bu=
t the > progress has been slower than I was hoping.

Please see my Ubuntu specific report at
https://bugs.launchpad.net/ubuntu/+source/glibc/+bug/1899800

My conclusion based on some tests of various distros and loads is that ther=
e's
a different bug also causing deadlocks in Ubuntu 18.04 that is fixed by 20.=
04
though even including the one-line mitigation patch here reduces the freque=
ncy
of deadlocks by orders of magnitude in the repo case.

Applied to Ubuntu 20.04 this one-line mitigation patch solves deadlocks
completely.

--=20
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