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From: "cvs-commit at gcc dot gnu.org" <sourceware-bugzilla@sourceware.org>
To: glibc-bugs@sourceware.org
Subject: [Bug libc/20975] Deferred cancellation triggers in __check_pf and
 looses lock leading to deadlock.
Date: Tue, 23 May 2023 23:41:20 +0000
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https://sourceware.org/bugzilla/show_bug.cgi?id=3D20975

--- Comment #8 from cvs-commit at gcc dot gnu.org <cvs-commit at gcc dot gn=
u.org> ---
The release/2.33/master branch has been updated by H.J. Lu
<hjl@sourceware.org>:

https://sourceware.org/git/gitweb.cgi?p=3Dglibc.git;h=3D24302748fcf85023fd6=
4630de241973ec17f2dc1

commit 24302748fcf85023fd64630de241973ec17f2dc1
Author: H.J. Lu <hjl.tools@gmail.com>
Date:   Thu Apr 27 13:06:15 2023 -0700

    __check_pf: Add a cancellation cleanup handler [BZ #20975]

    There are reports for hang in __check_pf:

    https://github.com/JoeDog/siege/issues/4

    It is reproducible only under specific configurations:

    1. Large number of cores (>=3D 64) and large number of threads (> 3X of
    the number of cores) with long lived socket connection.
    2. Low power (frequency) mode.
    3. Power management is enabled.

    While holding lock, __check_pf calls make_request which calls __sendto
    and __recvmsg.  Since __sendto and __recvmsg are cancellation points,
    lock held by __check_pf won't be released and can cause deadlock when
    thread cancellation happens in __sendto or __recvmsg.  Add a cancellati=
on
    cleanup handler for __check_pf to unlock the lock when cancelled by
    another thread.  This fixes BZ #20975 and the siege hang issue.

    (cherry picked from commit a443bd3fb233186038b8b483959ecb7978d1abea)

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