The branch main has been updated by markj: URL: https://cgit.FreeBSD.org/src/commit/?id=bb933b1d1846b3a984670b8cd65450c3333188f6
commit bb933b1d1846b3a984670b8cd65450c3333188f6 Author: Mark Johnston <[email protected]> AuthorDate: 2026-07-24 20:06:40 +0000 Commit: Mark Johnston <[email protected]> CommitDate: 2026-07-24 20:06:40 +0000 kqueue: Allocate marker knotes on the stack The scan marker was originally stack-allocated. In commit 1c0f9af5b5224, it became heap-allocated since the marker is visible to other threads and a scanning thread's stack may be swapped out. Now that kernel stacks can no longer be swapped out, we can avoid these heap allocations. Reviewed by: kib MFC after: 1 week Sponsored by: The FreeBSD Foundation Differential Revision: https://reviews.freebsd.org/D58402 --- sys/kern/kern_event.c | 29 +++++++++++++---------------- 1 file changed, 13 insertions(+), 16 deletions(-) diff --git a/sys/kern/kern_event.c b/sys/kern/kern_event.c index e19415c8d443..f22d8ca7da11 100644 --- a/sys/kern/kern_event.c +++ b/sys/kern/kern_event.c @@ -2109,7 +2109,7 @@ kqueue_scan(struct kqueue *kq, int maxevents, struct kevent_copyops *k_ops, const struct timespec *tsp, struct kevent *keva, struct thread *td) { struct kevent *kevp; - struct knote *kn, *marker; + struct knote *kn, marker; struct knlist *knl; sbintime_t asbt, rsbt; int count, error, haskqglobal, influx, nkev, touch; @@ -2148,8 +2148,8 @@ kqueue_scan(struct kqueue *kq, int maxevents, struct kevent_copyops *k_ops, asbt = -1; } else asbt = 0; - marker = knote_alloc(M_WAITOK); - marker->kn_status = KN_MARKER; + memset(&marker, 0, sizeof(marker)); + marker.kn_status = KN_MARKER; KQ_LOCK(kq); retry: @@ -2172,13 +2172,13 @@ retry: goto done; } - TAILQ_INSERT_TAIL(&kq->kq_head, marker, kn_tqe); + TAILQ_INSERT_TAIL(&kq->kq_head, &marker, kn_tqe); influx = 0; while (count) { KQ_OWNED(kq); kn = TAILQ_FIRST(&kq->kq_head); - if ((kn->kn_status == KN_MARKER && kn != marker) || + if ((kn->kn_status == KN_MARKER && kn != &marker) || kn_in_flux(kn)) { if (influx) { influx = 0; @@ -2196,7 +2196,7 @@ retry: kq->kq_count--; continue; } - if (kn == marker) { + if (kn == &marker) { KQ_FLUX_WAKEUP(kq); if (count == maxevents) goto retry; @@ -2294,11 +2294,10 @@ retry: break; } } - TAILQ_REMOVE(&kq->kq_head, marker, kn_tqe); + TAILQ_REMOVE(&kq->kq_head, &marker, kn_tqe); done: KQ_OWNED(kq); KQ_UNLOCK_FLUX(kq); - knote_free(marker); done_nl: KQ_NOTOWNED(kq); if (nkev != 0) @@ -3148,7 +3147,7 @@ kqueue_fork_copy(struct filedesc *fdp, struct file *fp, struct file *fp1, struct proc *p1, struct thread *td) { struct kqueue *kq, *kq1; - struct knote *marker; + struct knote marker; int error, i; error = 0; @@ -3157,26 +3156,24 @@ kqueue_fork_copy(struct filedesc *fdp, struct file *fp, struct file *fp1, kq1 = fp1->f_data; kq = kq1->kq_forksrc; - marker = knote_alloc(M_WAITOK); - marker->kn_status = KN_MARKER; - marker->kn_kq = kq; + memset(&marker, 0, sizeof(marker)); + marker.kn_status = KN_MARKER; + marker.kn_kq = kq; KQ_LOCK(kq); for (i = 0; i < kq->kq_knlistsize; i++) { - kqueue_fork_copy_list(&kq->kq_knlist[i], marker, kq, kq1, + kqueue_fork_copy_list(&kq->kq_knlist[i], &marker, kq, kq1, p1, fdp); } if (kq->kq_knhashmask != 0) { for (i = 0; i <= kq->kq_knhashmask; i++) { - kqueue_fork_copy_list(&kq->kq_knhash[i], marker, kq, + kqueue_fork_copy_list(&kq->kq_knhash[i], &marker, kq, kq1, p1, fdp); } } kqueue_release(kq, 1); kq1->kq_forksrc = NULL; KQ_UNLOCK_FLUX(kq); - - knote_free(marker); return (error); }
