Date: Mon, 06 Sep 2021 11:20:31 +0000 From: bugzilla-noreply@freebsd.org To: bugs@FreeBSD.org Subject: [Bug 258310] kevent() does not see signal with zero timeout Message-ID: <bug-258310-227-dJ6byTqe7r@https.bugs.freebsd.org/bugzilla/> In-Reply-To: <bug-258310-227@https.bugs.freebsd.org/bugzilla/> References: <bug-258310-227@https.bugs.freebsd.org/bugzilla/>
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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D258310 Konstantin Belousov <kib@FreeBSD.org> changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |kib@FreeBSD.org --- Comment #1 from Konstantin Belousov <kib@FreeBSD.org> --- So the problem is actually not that kevent does not get signal notification= .=20 It is that kqueue attached to kqueue with the signal event suddenly reports no events when you specify zero timeout, i.e. non-blocking peek. Am I right? This is because kqueue subsystem has to fight with the recursion and deadlo= ck. If kqueue has another kqueue attached to it, then notification of the attac= hed kqueue is delegated to a task. See knote_enqueue()->kqueue_wakeup()-> kqueue_schedtask(). Until task run, kq->kq_count =3D=3D 0 and this together with timespec being 0 (AKA unset) causes kqueue_scan() to immediately retur= n 0. I am not sure if this is worth complications to make the wakeup synchronous. --=20 You are receiving this mail because: You are the assignee for the bug.=
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