The branch main has been updated by kevans: URL: https://cgit.FreeBSD.org/src/commit/?id=c6dd40f2d35d596ca60a5d87616c3e4a0fd4f676
commit c6dd40f2d35d596ca60a5d87616c3e4a0fd4f676 Author: Kyle Evans <[email protected]> AuthorDate: 2026-04-09 02:37:00 +0000 Commit: Kyle Evans <[email protected]> CommitDate: 2026-04-09 02:37:11 +0000 kqueue: slightly clarify the flow in knlist_cleardel() This is purely a cosmetic change to make it a little easier on the eyes, rather than jumping back to the else branch up top. Re-flow it to use another loop on the outside and just inline the re-lock before we repeat after awaking from fluxwait. The !killkn path should maybe issue a wakeup if there's a thread in KQ_SLEEP so that userland can observe the EOF, but this isn't a practical problem today: pretty much every case of knlist_clear is tied to a file descriptor and called in the close(2) path. As a consequence, potentially affected knotes are almost always destroyed before we even get to knlist_clear(). Reviewed by: kib, markj Differential Revision: https://reviews.freebsd.org/D56226 --- sys/kern/kern_event.c | 50 +++++++++++++++++++++++++++++--------------------- 1 file changed, 29 insertions(+), 21 deletions(-) diff --git a/sys/kern/kern_event.c b/sys/kern/kern_event.c index 1deb7a705c56..01731ca46b6b 100644 --- a/sys/kern/kern_event.c +++ b/sys/kern/kern_event.c @@ -2792,31 +2792,39 @@ knlist_cleardel(struct knlist *knl, struct thread *td, int islocked, int killkn) KNL_ASSERT_LOCKED(knl); else { KNL_ASSERT_UNLOCKED(knl); -again: /* need to reacquire lock since we have dropped it */ knl->kl_lock(knl->kl_lockarg); } - SLIST_FOREACH_SAFE(kn, &knl->kl_list, kn_selnext, kn2) { - kq = kn->kn_kq; - KQ_LOCK(kq); - if (kn_in_flux(kn)) { - KQ_UNLOCK(kq); - continue; - } - knlist_remove_kq(knl, kn, 1, 1); - if (killkn) { - kn_enter_flux(kn); - KQ_UNLOCK(kq); - knote_drop_detached(kn, td); - } else { - /* Make sure cleared knotes disappear soon */ - kn->kn_flags |= EV_EOF | EV_ONESHOT; - KQ_UNLOCK(kq); + for (;;) { + /* + * Each pass removes as many knotes as we can before dropping + * into FLUXWAIT. Active knotes are simply detached and either + * freed or converted to one-shot, as the attached subject is + * essentially disappearing. + */ + SLIST_FOREACH_SAFE(kn, &knl->kl_list, kn_selnext, kn2) { + kq = kn->kn_kq; + KQ_LOCK(kq); + if (kn_in_flux(kn)) { + KQ_UNLOCK(kq); + continue; + } + knlist_remove_kq(knl, kn, 1, 1); + if (killkn) { + kn_enter_flux(kn); + KQ_UNLOCK(kq); + knote_drop_detached(kn, td); + } else { + /* Make sure cleared knotes disappear soon */ + kn->kn_flags |= EV_EOF | EV_ONESHOT; + KQ_UNLOCK(kq); + } + kq = NULL; } - kq = NULL; - } - if (!SLIST_EMPTY(&knl->kl_list)) { + if (SLIST_EMPTY(&knl->kl_list)) + break; + /* there are still in flux knotes remaining */ kn = SLIST_FIRST(&knl->kl_list); kq = kn->kn_kq; @@ -2826,7 +2834,7 @@ again: /* need to reacquire lock since we have dropped it */ kq->kq_state |= KQ_FLUXWAIT; msleep(kq, &kq->kq_lock, PSOCK | PDROP, "kqkclr", 0); kq = NULL; - goto again; + knl->kl_lock(knl->kl_lockarg); } if (islocked)
