From: Milton Miller <miltonm@bga.com>
To: Christian Borntraeger <borntraeger@de.ibm.com>,
Benjiman Herrenschmidt <benh@kernel.crashing.org>
Cc: linuxppc-dev list <linuxppc-dev@ozlabs.org>,
lkml <linux-kernel@vger.kernel.org>,
Alan Cox <alan@lxorguk.ukuu.org.uk>,
Joe Peterson <joe@skyrush.com>
Subject: [PATCH 0/5] hvc_console updates was Re: [BUG] hvc_console WARN() on current upstream
Date: Thu, 08 Jan 2009 06:12:58 -0600 [thread overview]
Message-ID: <hvc-console-29-3@bga.com> (raw)
In-Reply-To: <20090108111116.3f806d67@lxorguk.ukuu.org.uk>
Alan Cox wrote:
> Benjamin Herrenschmidt wrote:
>> Seems that we are in interrupt, doing hvc_poll, which does
>> tty_flip_buffer_push
>
>Which means that someone has tty->low_latency set and is calling
>tty_flip_buffer_push in an IRQ. That has never been allowed or safe, and
>now it hurts ;)
>
>/**
> * tty_flip_buffer_push - terminal
> * @tty: tty to push
> *
> * Queue a push of the terminal flip buffers to the line discipline.
>This
> * function must not be called from IRQ context if tty->low_latency
>is set *
> * In the event of the queue being busy for flipping the work will be
> * held off and retried later.
> *
> * Locking: tty buffer lock. Driver locks in low latency mode.
> */
>
>
>That comment has been there for some years in varying formats
>
I actually was preparing a patch for this problem after I had encountered
the a deadlock due to this. That is in the first patch. I then found
and made a few more cleanups, although I might have reordered the rest.
The history for setting low_latency is in the changelog of the first patch..
milton
WARNING: multiple messages have this Message-ID (diff)
From: Milton Miller <miltonm@bga.com>
To: Christian Borntraeger <borntraeger@de.ibm.com>,
Benjiman Herrenschmidt <benh@kernel.crashing.org>
Cc: linuxppc-dev list <linuxppc-dev@ozlabs.org>,
lkml <linux-kernel@vger.kernel.org>,
Joe Peterson <joe@skyrush.com>,
Alan Cox <alan@lxorguk.ukuu.org.uk>
Subject: [PATCH 0/5] hvc_console updates was Re: [BUG] hvc_console WARN() on current upstream
Date: Thu, 08 Jan 2009 06:12:58 -0600 [thread overview]
Message-ID: <hvc-console-29-3@bga.com> (raw)
In-Reply-To: <20090108111116.3f806d67@lxorguk.ukuu.org.uk>
Alan Cox wrote:
> Benjamin Herrenschmidt wrote:
>> Seems that we are in interrupt, doing hvc_poll, which does
>> tty_flip_buffer_push
>
>Which means that someone has tty->low_latency set and is calling
>tty_flip_buffer_push in an IRQ. That has never been allowed or safe, and
>now it hurts ;)
>
>/**
> * tty_flip_buffer_push - terminal
> * @tty: tty to push
> *
> * Queue a push of the terminal flip buffers to the line discipline.
>This
> * function must not be called from IRQ context if tty->low_latency
>is set *
> * In the event of the queue being busy for flipping the work will be
> * held off and retried later.
> *
> * Locking: tty buffer lock. Driver locks in low latency mode.
> */
>
>
>That comment has been there for some years in varying formats
>
I actually was preparing a patch for this problem after I had encountered
the a deadlock due to this. That is in the first patch. I then found
and made a few more cleanups, although I might have reordered the rest.
The history for setting low_latency is in the changelog of the first patch..
milton
next prev parent reply other threads:[~2009-01-08 12:13 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-01-08 5:18 [BUG] hvc_console WARN() on current upstream Benjamin Herrenschmidt
2009-01-08 7:57 ` Christian Borntraeger
2009-01-08 8:42 ` Benjamin Herrenschmidt
2009-01-08 11:11 ` Alan Cox
2009-01-08 12:12 ` Milton Miller [this message]
2009-01-08 12:12 ` [PATCH 0/5] hvc_console updates was " Milton Miller
2009-01-08 12:14 ` [PATCH 4/4] hvc_console: comment mb and make it an smp_ one Milton Miller
2009-01-08 12:14 ` [PATCH 3/4] hvc_console: free_irq only if request_irq was successful Milton Miller
2009-01-08 12:14 ` Milton Miller
2009-01-08 16:50 ` Christian Borntraeger
2009-01-08 16:50 ` Christian Borntraeger
2009-01-08 12:14 ` [PATCH 1/4] hvc_console: do not set low_latency Milton Miller
2009-01-08 12:14 ` Milton Miller
2009-01-08 12:36 ` Alan Cox
2009-01-08 12:36 ` Alan Cox
2009-01-08 13:25 ` Milton Miller
2009-01-08 13:25 ` Milton Miller
2009-01-13 9:04 ` Christian Borntraeger
2009-01-13 9:04 ` Christian Borntraeger
2009-01-13 11:28 ` Christian Borntraeger
2009-01-13 11:28 ` Christian Borntraeger
2009-01-13 11:35 ` Hendrik Brueckner
2009-01-13 11:35 ` Hendrik Brueckner
2009-01-13 16:03 ` Milton Miller
2009-01-13 16:03 ` Milton Miller
2009-01-13 21:04 ` Benjamin Herrenschmidt
2009-01-13 21:04 ` Benjamin Herrenschmidt
2009-01-15 9:15 ` [PATCH 1/4 v2] hvc_console: remove tty->low_latency Hendrik Brueckner
2009-01-15 9:15 ` Hendrik Brueckner
2009-01-15 9:17 ` Christian Borntraeger
2009-01-15 9:17 ` Christian Borntraeger
2009-01-08 12:14 ` [PATCH 2/4] hvc_console: use kzalloc Milton Miller
2009-01-08 12:14 ` Milton Miller
2009-01-08 20:36 ` [BUG] hvc_console WARN() on current upstream Benjamin Herrenschmidt
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