From: Tomi Valkeinen <tomi.valkeinen@ti.com>
To: "Pali Rohár" <pali.rohar@gmail.com>,
"Jean-Christophe Plagniol-Villard" <plagnioj@jcrosoft.com>,
"Jyri Sarha" <jsarha@ti.com>
Cc: linux-omap@vger.kernel.org, linux-fbdev@vger.kernel.org,
linux-kernel@vger.kernel.org, Pavel Machek <pavel@ucw.cz>,
Sebastian Reichel <sre@kernel.org>,
Aaro Koskinen <aaro.koskinen@iki.fi>,
Tony Lindgren <tony@atomide.com>, Nishanth Menon <nm@ti.com>
Subject: Re: omapdss: Division by zero in kernel
Date: Fri, 21 Aug 2015 08:42:14 +0000 [thread overview]
Message-ID: <55D6E466.5060706@ti.com> (raw)
In-Reply-To: <201507241803.42891@pali>
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On 24/07/15 19:03, Pali Rohár wrote:
> Hello,
>
> when on N900 (real HW or qemu) I run this command
>
> / # echo 0 > /sys/devices/platform/omapdss/overlay0/enabled && echo 0 > /sys/class/graphics/fb0/size
>
> then kernel crash with this error message
>
> / # [ 29.904113] Division by zero in kernel.
The problem is that fb console uses the kernel mmapped framebuffer, but
omapfb is not aware of the fb console. So the above commands free the
framebuffer, as omapfb thinks no one is using it, and then fb console
tries to touch the fb.
omapfb tracks mmaps from userspace, and refuses to free a fb it it's
mmapped.
I don't know how to fix it straight away. Maybe there's a way for omapfb
to check if the fbcon uses the fb in question, and if so, refuses to
release/resize the memory.
Tomi
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WARNING: multiple messages have this Message-ID (diff)
From: Tomi Valkeinen <tomi.valkeinen@ti.com>
To: "Pali Rohár" <pali.rohar@gmail.com>,
"Jean-Christophe Plagniol-Villard" <plagnioj@jcrosoft.com>,
"Jyri Sarha" <jsarha@ti.com>
Cc: linux-omap@vger.kernel.org, linux-fbdev@vger.kernel.org,
linux-kernel@vger.kernel.org, Pavel Machek <pavel@ucw.cz>,
Sebastian Reichel <sre@kernel.org>,
Aaro Koskinen <aaro.koskinen@iki.fi>,
Tony Lindgren <tony@atomide.com>, Nishanth Menon <nm@ti.com>
Subject: Re: omapdss: Division by zero in kernel
Date: Fri, 21 Aug 2015 11:42:14 +0300 [thread overview]
Message-ID: <55D6E466.5060706@ti.com> (raw)
In-Reply-To: <201507241803.42891@pali>
[-- Attachment #1: Type: text/plain, Size: 829 bytes --]
On 24/07/15 19:03, Pali Rohár wrote:
> Hello,
>
> when on N900 (real HW or qemu) I run this command
>
> / # echo 0 > /sys/devices/platform/omapdss/overlay0/enabled && echo 0 > /sys/class/graphics/fb0/size
>
> then kernel crash with this error message
>
> / # [ 29.904113] Division by zero in kernel.
The problem is that fb console uses the kernel mmapped framebuffer, but
omapfb is not aware of the fb console. So the above commands free the
framebuffer, as omapfb thinks no one is using it, and then fb console
tries to touch the fb.
omapfb tracks mmaps from userspace, and refuses to free a fb it it's
mmapped.
I don't know how to fix it straight away. Maybe there's a way for omapfb
to check if the fbcon uses the fb in question, and if so, refuses to
release/resize the memory.
Tomi
[-- Attachment #2: OpenPGP digital signature --]
[-- Type: application/pgp-signature, Size: 819 bytes --]
WARNING: multiple messages have this Message-ID (diff)
From: Tomi Valkeinen <tomi.valkeinen@ti.com>
To: "Pali Rohár" <pali.rohar@gmail.com>,
"Jean-Christophe Plagniol-Villard" <plagnioj@jcrosoft.com>,
"Jyri Sarha" <jsarha@ti.com>
Cc: <linux-omap@vger.kernel.org>, <linux-fbdev@vger.kernel.org>,
<linux-kernel@vger.kernel.org>, Pavel Machek <pavel@ucw.cz>,
Sebastian Reichel <sre@kernel.org>,
Aaro Koskinen <aaro.koskinen@iki.fi>,
Tony Lindgren <tony@atomide.com>, Nishanth Menon <nm@ti.com>
Subject: Re: omapdss: Division by zero in kernel
Date: Fri, 21 Aug 2015 11:42:14 +0300 [thread overview]
Message-ID: <55D6E466.5060706@ti.com> (raw)
In-Reply-To: <201507241803.42891@pali>
[-- Attachment #1: Type: text/plain, Size: 829 bytes --]
On 24/07/15 19:03, Pali Rohár wrote:
> Hello,
>
> when on N900 (real HW or qemu) I run this command
>
> / # echo 0 > /sys/devices/platform/omapdss/overlay0/enabled && echo 0 > /sys/class/graphics/fb0/size
>
> then kernel crash with this error message
>
> / # [ 29.904113] Division by zero in kernel.
The problem is that fb console uses the kernel mmapped framebuffer, but
omapfb is not aware of the fb console. So the above commands free the
framebuffer, as omapfb thinks no one is using it, and then fb console
tries to touch the fb.
omapfb tracks mmaps from userspace, and refuses to free a fb it it's
mmapped.
I don't know how to fix it straight away. Maybe there's a way for omapfb
to check if the fbcon uses the fb in question, and if so, refuses to
release/resize the memory.
Tomi
[-- Attachment #2: OpenPGP digital signature --]
[-- Type: application/pgp-signature, Size: 819 bytes --]
next prev parent reply other threads:[~2015-08-21 8:42 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-07-24 16:03 omapdss: Division by zero in kernel Pali Rohár
2015-07-24 16:03 ` Pali Rohár
2015-07-28 11:56 ` Pali Rohár
2015-07-28 11:56 ` Pali Rohár
2015-08-18 14:00 ` Pali Rohár
2015-08-18 14:00 ` Pali Rohár
2015-08-18 14:11 ` Peter Teoh
2015-08-18 14:11 ` Peter Teoh
2015-08-19 8:11 ` Pali Rohár
2015-08-19 8:11 ` Pali Rohár
2015-09-17 5:16 ` Pavel Machek
2015-09-17 5:16 ` Pavel Machek
2015-09-25 11:34 ` Pali Rohár
2015-09-25 11:34 ` Pali Rohár
2015-08-21 8:42 ` Tomi Valkeinen [this message]
2015-08-21 8:42 ` Tomi Valkeinen
2015-08-21 8:42 ` Tomi Valkeinen
2015-08-21 8:48 ` Pali Rohár
2015-08-21 8:48 ` Pali Rohár
2015-08-21 9:17 ` Tomi Valkeinen
2015-08-21 9:17 ` Tomi Valkeinen
2015-08-21 9:17 ` Tomi Valkeinen
2015-08-26 10:16 ` Pali Rohár
2015-08-26 10:16 ` Pali Rohár
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