git: f5a145cb0a5f - stable/13 - PP mutexes: lock: Check if priority is too high against base one
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Date: Thu, 09 May 2024 13:30:19 UTC
The branch stable/13 has been updated by olce: URL: https://cgit.FreeBSD.org/src/commit/?id=f5a145cb0a5f5ca0eef54d35d60f765639c8f30a commit f5a145cb0a5f5ca0eef54d35d60f765639c8f30a Author: Olivier Certner <olce@FreeBSD.org> AuthorDate: 2024-02-22 08:53:51 +0000 Commit: Olivier Certner <olce@FreeBSD.org> CommitDate: 2024-05-09 13:29:18 +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 5767a137b536..05a47f405d30 100644 --- a/sys/kern/kern_umtx.c +++ b/sys/kern/kern_umtx.c @@ -2552,7 +2552,7 @@ 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;