Date: Wed, 14 Sep 2011 07:40:17 -0400 From: John Baldwin <jhb@freebsd.org> To: freebsd-net@freebsd.org Cc: Ryan Stone <rysto32@gmail.com>, Jack Vogel <jfvogel@gmail.com>, Arnaud Lacombe <lacombar@gmail.com> Subject: Re: FreeBSD 7-STABLE mbuf corruption Message-ID: <201109140740.17319.jhb@freebsd.org> In-Reply-To: <CAFMmRNwrD-v52iW5%2Bw_hbgL9battHjXSKcOWBTiMnBHM-cURXg@mail.gmail.com> References: <CACqU3MUs9Z9GeuGe=8iVp=MWV6eG-tO%2BkHb1znatsTq2uEqwvA@mail.gmail.com> <CACqU3MV7JRxQ_mNeHCk7RVyzETZLAcc3XL=xyZ-qqtPfRxkZeQ@mail.gmail.com> <CAFMmRNwrD-v52iW5%2Bw_hbgL9battHjXSKcOWBTiMnBHM-cURXg@mail.gmail.com>
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On Tuesday, September 13, 2011 6:29:05 pm Ryan Stone wrote:
> On Tue, Sep 13, 2011 at 2:36 PM, Arnaud Lacombe <lacombar@gmail.com> wrote:
> > It did not crash, yet. The only downside is that after 3h30 and ~4h,
> > igb(4) queues' handler started spinning infinitely, breaking network
> > connectivity.
>
> I saw a similar issue on HEAD last week. The attached patch fix the
> problem for me. The problem was that if a struct task's ta_pending
> field overflows, the task will be inserted into a list when it is
> already in that list, causing a cycle in the list of tasks to be run.
> This causes the taskqueue thread to spin indefinitely as it looks over
> the cycle again and again.
>
> In case the list eats the patch, it was:
>
> Index: sys/kern/subr_taskqueue.c
> ===================================================================
> --- sys/kern/subr_taskqueue.c (revision 225537)
> +++ sys/kern/subr_taskqueue.c (working copy)
> @@ -173,7 +173,8 @@
> * Count multiple enqueues.
> */
> if (task->ta_pending) {
> - task->ta_pending++;
> + if (task->ta_pending < UINT16_MAX)
> + task->ta_pending++;
> return (0);
> }
You should probably commit that. I wonder if it should be a KASSERT() also so
that it outright panics on a kernel with INVARIANTS enabled so developers will
go fix their code as it seems to me to likely be a bug to enqueue a task that
many times.
--
John Baldwin
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