The branch main has been updated by markj:
URL:
https://cgit.FreeBSD.org/src/commit/?id=4b79443927ec2c53514e73b06eb2a9d241882585
commit 4b79443927ec2c53514e73b06eb2a9d241882585
Author: Mark Johnston <ma...@freebsd.org>
AuthorDate: 2025-02-22 01:23:31 +0000
Commit: Mark Johnston <ma...@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 <dmk...@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;
}
/*
