[Bug 265997] compat10 semaphore interface internal race may lead to application hang

https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=265997

--- Comment #2 from commit-hook@FreeBSD.org ---
A commit in branch main references this bug:

URL:
https://cgit.FreeBSD.org/src/commit/?id=768f6373eb3d60e346d3bfa495e04315aeed8ff9

commit 768f6373eb3d60e346d3bfa495e04315aeed8ff9
Author:     firk <firk@cantconnect.ru>
AuthorDate: 2022-08-26 08:05:56 +0000
Commit:     Konstantin Belousov <kib@FreeBSD.org>
CommitDate: 2022-08-26 17:34:29 +0000

    Fix compat10 semaphore interface race

    Wrong has-waiters and missing unconditional _count==0 check may cause
    infinite waiting with already non-zero count.
    1) properly clear _has_waiters flag when waiting failed to start
    2) always check _count before start waiting

    PR:     265997
    Reviewed by:    kib
    MFC after:      1 week
    Differential revision:  https://reviews.freebsd.org/D36272

 sys/kern/kern_umtx.c | 24 ++++++++++++++----------
 1 file changed, 14 insertions(+), 10 deletions(-)

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