Date: Sat, 22 Feb 2025 01:26:56 GMT From: Mark Johnston <markj@FreeBSD.org> To: src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-main@FreeBSD.org Subject: git: 4b79443927ec - main - umtx: Fix a bug in do_lock_pp() Message-ID: <202502220126.51M1Qufx006885@gitrepo.freebsd.org>
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The branch main has been updated by markj: URL: https://cgit.FreeBSD.org/src/commit/?id=4b79443927ec2c53514e73b06eb2a9d241882585 commit 4b79443927ec2c53514e73b06eb2a9d241882585 Author: Mark Johnston <markj@FreeBSD.org> AuthorDate: 2025-02-22 01:23:31 +0000 Commit: Mark Johnston <markj@FreeBSD.org> CommitDate: 2025-02-22 01:26:38 +0000 umtx: Fix a bug in do_lock_pp() If the lock is unowned (i.e., owner == UMUTEX_CONTESTED), we might get a spurious failure, and in that case we need to retry the loop. Otherwise, the calling thread can end up sleeping forever. The same problem exists in do_set_ceiling(), which open-codes do_lock_pp(), so fix it there too. Reviewed by: olce Reported by: Daniel King <dmking@adacore.com> MFC after: 2 weeks Sponsored by: Innovate UK Differential Revision: https://reviews.freebsd.org/D49031 --- sys/kern/kern_umtx.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/sys/kern/kern_umtx.c b/sys/kern/kern_umtx.c index 938dcf2ff1cb..f9189024d629 100644 --- a/sys/kern/kern_umtx.c +++ b/sys/kern/kern_umtx.c @@ -2616,6 +2616,10 @@ do_lock_pp(struct thread *td, struct umutex *m, uint32_t flags, } } else if (owner == UMUTEX_RB_NOTRECOV) { error = ENOTRECOVERABLE; + } else if (owner == UMUTEX_CONTESTED) { + /* Spurious failure, retry. */ + umtxq_unbusy_unlocked(&uq->uq_key); + continue; } if (try != 0) @@ -2825,6 +2829,10 @@ do_set_ceiling(struct thread *td, struct umutex *m, uint32_t ceiling, } else if (owner == UMUTEX_RB_NOTRECOV) { error = ENOTRECOVERABLE; break; + } else if (owner == UMUTEX_CONTESTED) { + /* Spurious failure, retry. */ + umtxq_unbusy_unlocked(&uq->uq_key); + continue; } /*
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