The branch main has been updated by andrew: URL: https://cgit.FreeBSD.org/src/commit/?id=11a6ecd4258b9108fb19420ec5db297f6d99a842
commit 11a6ecd4258b9108fb19420ec5db297f6d99a842 Author: Andrew Turner <[email protected]> AuthorDate: 2022-05-09 14:28:56 +0000 Commit: Andrew Turner <[email protected]> CommitDate: 2022-05-19 10:30:21 +0000 Handle cas failure when the compare succeeds When locking a priority inherit mutex we perform a compare and swap operation to try and acquire the mutex. This may fail even when the compare succeeds. Check and handle this case. PR: 263825 Reviewed by: kib, markj Sponsored by: The FreeBSD Foundation Differential Revision: https://reviews.freebsd.org/D35150 --- sys/kern/kern_umtx.c | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/sys/kern/kern_umtx.c b/sys/kern/kern_umtx.c index 2f666bdcdc7b..d63381d76eb8 100644 --- a/sys/kern/kern_umtx.c +++ b/sys/kern/kern_umtx.c @@ -2262,6 +2262,17 @@ do_lock_pi(struct thread *td, struct umutex *m, uint32_t flags, break; } + /* + * Nobody owns it, but the acquire failed. This can happen + * with ll/sc atomics. + */ + if (owner == UMUTEX_UNOWNED) { + error = thread_check_susp(td, true); + if (error != 0) + break; + continue; + } + /* * Avoid overwriting a possible error from sleep due * to the pending signal with suspension check result.
