git: 9ac3ac9ece62 - main - PP mutexes: lock: Check if priority is too high against base one
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Date: Tue, 27 Feb 2024 09:00:17 UTC
The branch main has been updated by olce:
URL: https://cgit.FreeBSD.org/src/commit/?id=9ac3ac9ece6269365ac314fa5fdb484e96d4a32e
commit 9ac3ac9ece6269365ac314fa5fdb484e96d4a32e
Author: Olivier Certner <olce@FreeBSD.org>
AuthorDate: 2024-02-22 08:53:51 +0000
Commit: Olivier Certner <olce@FreeBSD.org>
CommitDate: 2024-02-27 08:59:36 +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
---
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;