git: 9dad96bc6344 - releng/14.1 - PP mutexes: lock: Reduce 'umtx_lock' holding before taking the user lock
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Date: Tue, 14 May 2024 13:39:25 UTC
The branch releng/14.1 has been updated by olce: URL: https://cgit.FreeBSD.org/src/commit/?id=9dad96bc634429711f3a1f74a8f988d963e99d96 commit 9dad96bc634429711f3a1f74a8f988d963e99d96 Author: Olivier Certner <olce@FreeBSD.org> AuthorDate: 2024-02-22 09:13:38 +0000 Commit: Olivier Certner <olce@FreeBSD.org> CommitDate: 2024-05-14 13:37:35 +0000 PP mutexes: lock: Reduce 'umtx_lock' holding before taking the user lock There is no need to have it for the priority check (that the thread doesn't have a higher priority than the mutex's ceiling), and there's also no need to take it if the thread doesn't have privileges to set its priority to the mutex's ceiling. While here, turn 'su' into a 'bool' and compute the internal priority corresponding to the mutex's ceiling once and for all, putting it in new 'new_pri'. Reviewed by: kib Approved by: emaste (mentor) MFC after: 2 weeks Sponsored by: The FreeBSD Foundation Differential Revision: https://reviews.freebsd.org/D44045 (cherry picked from commit 39e4665c9694b9f9b07d1cfa85befc288cabe906) Approved by: emaste (mentor) (cherry picked from commit ce7dc52f07d05d00054d48faf00fcac4036d56df) Approved by: emaste (mentor) Approved by: re (cperciva) --- sys/kern/kern_umtx.c | 25 ++++++++++++++----------- 1 file changed, 14 insertions(+), 11 deletions(-) diff --git a/sys/kern/kern_umtx.c b/sys/kern/kern_umtx.c index 5abc1e71d763..092fcade9d19 100644 --- a/sys/kern/kern_umtx.c +++ b/sys/kern/kern_umtx.c @@ -2520,7 +2520,8 @@ do_lock_pp(struct thread *td, struct umutex *m, uint32_t flags, struct umtx_pi *pi; uint32_t ceiling; uint32_t owner, id; - int error, pri, old_inherited_pri, su, rv; + int error, pri, old_inherited_pri, new_pri, rv; + bool su; id = td->td_tid; uq = td->td_umtxq; @@ -2549,21 +2550,23 @@ do_lock_pp(struct thread *td, struct umutex *m, uint32_t flags, error = EINVAL; goto out; } + new_pri = PRI_MIN_REALTIME + ceiling; - mtx_lock(&umtx_lock); - if (td->td_base_user_pri < PRI_MIN_REALTIME + ceiling) { - mtx_unlock(&umtx_lock); + if (td->td_base_user_pri < new_pri) { error = EINVAL; goto out; } - if (su && PRI_MIN_REALTIME + ceiling < uq->uq_inherited_pri) { - uq->uq_inherited_pri = PRI_MIN_REALTIME + ceiling; - thread_lock(td); - if (uq->uq_inherited_pri < UPRI(td)) - sched_lend_user_prio(td, uq->uq_inherited_pri); - thread_unlock(td); + if (su) { + mtx_lock(&umtx_lock); + if (new_pri < uq->uq_inherited_pri) { + uq->uq_inherited_pri = new_pri; + thread_lock(td); + if (new_pri < UPRI(td)) + sched_lend_user_prio(td, new_pri); + thread_unlock(td); + } + mtx_unlock(&umtx_lock); } - mtx_unlock(&umtx_lock); rv = casueword32(&m->m_owner, UMUTEX_CONTESTED, &owner, id | UMUTEX_CONTESTED);