Date: Tue, 20 Dec 2011 09:52:44 -0500 From: John Baldwin <jhb@freebsd.org> To: Pawel Jakub Dawidek <pjd@freebsd.org> Cc: Kostik Belousov <kostikbel@gmail.com>, Lawrence Stewart <lstewart@freebsd.org>, freebsd-current@freebsd.org, Andre Oppermann <andre@freebsd.org>, freebsd-net@freebsd.org Subject: Re: 9.0-RC1 panic in tcp_input: negative winow. Message-ID: <201112200952.44690.jhb@freebsd.org> In-Reply-To: <20111217232125.GA1685@garage.freebsd.pl> References: <20111022084931.GD1697@garage.freebsd.pl> <201112121100.23567.jhb@freebsd.org> <20111217232125.GA1685@garage.freebsd.pl>
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On Saturday, December 17, 2011 6:21:27 pm Pawel Jakub Dawidek wrote: > On Mon, Dec 12, 2011 at 11:00:23AM -0500, John Baldwin wrote: > > An update. I've sent Pawel a testing patch to see if my hypothesis is correct > > (www.freebsd.org/~jhb/patches/tcp_negwin_test.patch). If it is then I intend > > to commit www.freebsd.org/~jhb/patches/tcp_negwin2.patch as the fix. > > Unfortunately it paniced today. Take a look at: > > http://people.freebsd.org/~pjd/misc/tcp_panic.jpg Ok, the one use case I was worried about is happening regularly before your panic, so that is good. Can you use gdb to figure out which call to tcp_output() is actually panic'ing? I wonder if it is this case: /* * Return any desired output. */ if (needoutput || (tp->t_flags & TF_ACKNOW)) { (void) tcp_output(tp); /* XXX: Debug */ KASSERT(SEQ_GEQ(tp->rcv_adv, tp->rcv_nxt), ("tcp_input: negative window after ACK")); And if 'needoutput' is true, but TF_ACKNOW is not set, and tcp_output() decides to not do anything. I've updated tcp_negwin_test.patch to not panic if that call to tcp_output() doesn't actually send a packet. Please re-test. -- John Baldwin
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