Date: Thu, 9 May 2024 13:26:58 GMT From: Olivier Certner <olce@FreeBSD.org> To: src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-branches@FreeBSD.org Subject: git: f9e9c02241dc - stable/14 - PP mutexes: lock: Check if priority is too high against base one Message-ID: <202405091326.449DQwgG049603@gitrepo.freebsd.org>
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The branch stable/14 has been updated by olce: URL: https://cgit.FreeBSD.org/src/commit/?id=f9e9c02241dc887244cf62136dfcea04718290a0 commit f9e9c02241dc887244cf62136dfcea04718290a0 Author: Olivier Certner <olce@FreeBSD.org> AuthorDate: 2024-02-22 08:53:51 +0000 Commit: Olivier Certner <olce@FreeBSD.org> CommitDate: 2024-05-09 13:26:21 +0000 PP mutexes: lock: Check if priority is too high against base one Doing this instead of using the current (user) priority, which includes current lendings, prevents gratuitous failures for threads involved in multiple locking groups, where each group is defined as the threads that can lock a particular PP or PI mutex. No deadlock can occur in this case. Indeed, if a thread holds such a lock A giving it a higher priority than the ceiling of some other lock B that is PP, and B is acquired by another thread, effectively the latter may not be able to run but this situation can only last until the first thread releases A, which it will do eventually. Reviewed by: kib Approved by: emaste (mentor) MFC after: 2 weeks Sponsored by: The FreeBSD Foundation Differential Revision: https://reviews.freebsd.org/D44044 (cherry picked from commit 9ac3ac9ece6269365ac314fa5fdb484e96d4a32e) Approved by: emaste (mentor) --- 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 9c7225863bb1..5abc1e71d763 100644 --- a/sys/kern/kern_umtx.c +++ b/sys/kern/kern_umtx.c @@ -2551,7 +2551,7 @@ do_lock_pp(struct thread *td, struct umutex *m, uint32_t flags, } mtx_lock(&umtx_lock); - if (UPRI(td) < PRI_MIN_REALTIME + ceiling) { + if (td->td_base_user_pri < PRI_MIN_REALTIME + ceiling) { mtx_unlock(&umtx_lock); error = EINVAL; goto out;
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