Date: Wed, 8 Jun 2022 00:44:59 GMT From: Mark Johnston <markj@FreeBSD.org> To: src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-branches@FreeBSD.org Subject: git: 129112f80d2b - stable/13 - kevent: Fix an off-by-one in filt_timerexpire_l() Message-ID: <202206080044.2580ixka060660@gitrepo.freebsd.org>
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The branch stable/13 has been updated by markj: URL: https://cgit.FreeBSD.org/src/commit/?id=129112f80d2bfe6091ebb8656912fb55d6192e1f commit 129112f80d2bfe6091ebb8656912fb55d6192e1f Author: Mark Johnston <markj@FreeBSD.org> AuthorDate: 2022-05-25 00:14:33 +0000 Commit: Mark Johnston <markj@FreeBSD.org> CommitDate: 2022-06-08 00:42:21 +0000 kevent: Fix an off-by-one in filt_timerexpire_l() Suppose a periodic kevent timer fires close to its deadline, so that now - kc->next is small. Then delta ends up being 1, and the next timer deadline is set to (delta + 1) * kc->to, where kc->to is the timer period. This means that the timer fires at half of the requested rate, and the value returned in kn_data is similarly inaccurate. PR: 264131 Fixes: 7cb40543e964 ("filt_timerexpire: do not iterate over the interval") Reviewed by: kib Sponsored by: The FreeBSD Foundation (cherry picked from commit 524dadf7a8725dea144571843e611dbdbd59d668) --- sys/kern/kern_event.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/sys/kern/kern_event.c b/sys/kern/kern_event.c index 1e6968326b6c..832962d42a4d 100644 --- a/sys/kern/kern_event.c +++ b/sys/kern/kern_event.c @@ -739,7 +739,7 @@ filt_timerexpire_l(struct knote *kn, bool proc_locked) if (delta == 0) delta = 1; kn->kn_data += delta; - kc->next += (delta + 1) * kc->to; + kc->next += delta * kc->to; if (now >= kc->next) /* overflow */ kc->next = now + kc->to; KNOTE_ACTIVATE(kn, 0); /* XXX - handle locking */
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