Date: Thu, 2 Apr 2026 16:01:42 +0300 From: Konstantin Belousov <kostikbel@gmail.com> To: current@freebsd.org Subject: Re: Panic: "knote ... was already on knlist..." after main-n284826-d9d7b5948649 Message-ID: <ac5otmIUJkRwNY8q@kib.kiev.ua> In-Reply-To: <ac5mIAT2mREod9OK@albert.catwhisker.org>
index | next in thread | previous in thread | raw e-mail
On Thu, Apr 02, 2026 at 05:50:40AM -0700, David Wolfskill wrote: > Build machine (kernel GENERIC) did not experience this. So far, 3 out > of 3 laptops have (the 4th one has yet to finish the build). > > I snapped a photo, which is up at > https://www.catwhisker.org/~david/FreeBSD/head/n284826/screen.jpg > > The panic occurs during the late(r) part of the transition to multi-user > mode. I am happy to poke at one of the machines, given suitable clues: > I tend to break stuff. > > The machines had previously built and run main-n284804-f3b59bf28504. > All machines are amd64, and I use PORTS_MODULES in /etc/src.conf to > ensure that ports-resident kernel modules get rebuilt whenever the > kernel does./~david/FreeBSD/head/n284826/screen.jpg > > The panic occurs during the late(r) part of the transition to multi-user > mode. I am happy to poke at one of the machines, given suitable clues: > I tend to break stuff. > > A quick scan down the backtrace shows: > db_trace_self_wrapper() > vpanic() > panic() > knlist_remove() > kqueue_fork_copy_list() > kqueue_fork() > fdcopy() > do_fork() > fork() > sys_fork() > amd64_syscall() > fast_syscall_common() > --- syscall > KDB: enter: panic > [ thread pid 1891 tld 100578 ] > Stopped at xffffffffff88c177c3 = kdb_enter+0x33: movq $0,0x15f7842(%rip) > db> Peter Holm already reported this or similar issue. Try this please. commit 5da1dcf8b88ffa3591a84405a8ab29ebd846f2e0 Author: Konstantin Belousov <kib@FreeBSD.org> Date: Thu Apr 2 14:02:14 2026 +0300 kqueue_fork_copy_knote(): zero kn_knlist for the copy before calling knlist_add() Reported by: pho Sponsored by: The FreeBSD Foundation MFC after: 1 week diff --git a/sys/kern/kern_event.c b/sys/kern/kern_event.c index dc9e8b71ea13..5b0a3e59b715 100644 --- a/sys/kern/kern_event.c +++ b/sys/kern/kern_event.c @@ -3103,6 +3103,7 @@ kqueue_fork_copy_knote(struct kqueue *kq1, struct knote *kn, struct proc *p1, kn1->kn_status |= KN_DETACHED; kn1->kn_status &= ~KN_QUEUED; kn1->kn_kq = kq1; + kn1->kn_knlist = NULL; error = fop->f_copy(kn1, p1); if (error != 0) { knote_free(kn1);home | help
Want to link to this message? Use this
URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?ac5otmIUJkRwNY8q>