git: 524dadf7a872 - main - kevent: Fix an off-by-one in filt_timerexpire_l()
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Date: Wed, 25 May 2022 00:18:18 UTC
The branch main has been updated by markj: URL: https://cgit.FreeBSD.org/src/commit/?id=524dadf7a8725dea144571843e611dbdbd59d668 commit 524dadf7a8725dea144571843e611dbdbd59d668 Author: Mark Johnston <markj@FreeBSD.org> AuthorDate: 2022-05-25 00:14:33 +0000 Commit: Mark Johnston <markj@FreeBSD.org> CommitDate: 2022-05-25 00:14:33 +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 MFC after: 2 weeks Sponsored by: The FreeBSD Foundation Differential Revision: https://reviews.freebsd.org/D35313 --- 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 33607fe8c5f4..f1ee8de4e7ee 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 */