Date: Mon, 17 Feb 2025 16:41:07 GMT From: Bojan =?utf-8?Q?Novkovi=C4=87?= <bnovkov@FreeBSD.org> To: src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-main@FreeBSD.org Subject: git: df436036e82b - main - umtx: Don't sleep after casueword32 failure in do_sem2_wake Message-ID: <202502171641.51HGf7d3094254@gitrepo.freebsd.org>
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The branch main has been updated by bnovkov: URL: https://cgit.FreeBSD.org/src/commit/?id=df436036e82b895a6233d803bc8bf14d2cfe90d7 commit df436036e82b895a6233d803bc8bf14d2cfe90d7 Author: Bojan Novković <bnovkov@FreeBSD.org> AuthorDate: 2025-01-30 15:10:04 +0000 Commit: Bojan Novković <bnovkov@FreeBSD.org> CommitDate: 2025-02-17 16:40:34 +0000 umtx: Don't sleep after casueword32 failure in do_sem2_wake When a casueword32 operation fails, 'do_sem2_wake' will call 'thread_check_susp' to avoid a potential livelock. However, it instructs 'thread_check_susp' to sleep while holding a previously busied umtxq key. This is explicitly discouraged by the comments in 'thread_check_susp' which state that a thread shouldn't sleep if it owns a kernel resource. Fix this by passing 'false' to 'thread_check_susp'. Reviewed by: kib PR: 282713 Differential Revision: https://reviews.freebsd.org/D48728 Sponsored by: Klara Inc. --- sys/kern/kern_umtx.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/sys/kern/kern_umtx.c b/sys/kern/kern_umtx.c index a9294c324cb4..938dcf2ff1cb 100644 --- a/sys/kern/kern_umtx.c +++ b/sys/kern/kern_umtx.c @@ -3789,7 +3789,7 @@ do_sem2_wake(struct thread *td, struct _usem2 *sem) rv = casueword32(&sem->_count, count, &count, count & ~USEM_HAS_WAITERS); if (rv == 1) { - rv = thread_check_susp(td, true); + rv = thread_check_susp(td, false); if (rv != 0) break; }
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