linux-kernel - Re: [PATCH] drm: avoid switching to text console if there is no panic timeout

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Date:	Tue, 18 Oct 2011 10:22:55 +0800
From:	Dave Young <hidave.darkstar@...il.com>
To:	Mandeep Singh Baines <msb@...omium.org>
Cc:	linux-kernel@...r.kernel.org, David Airlie <airlied@...ux.ie>,
	Hugh Dickins <hughd@...omium.org>,
	Hugh Dickins <hughd@...gle.com>,
	Dave Airlie <airlied@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	dri-devel@...ts.freedesktop.org
Subject: Re: [PATCH] drm: avoid switching to text console if there is no panic timeout

On Tue, Oct 18, 2011 at 10:19 AM, Dave Young <hidave.darkstar@...il.com> wrote:
> On Tue, Oct 18, 2011 at 8:06 AM, Mandeep Singh Baines <msb@...omium.org> wrote:
>> From: Hugh Dickins <hughd@...omium.org>
>>
>> Add a check for panic_timeout in the drm_fb_helper_panic() notifier: if
>> we're going to reboot immediately, the user will not be able to see the
>> messages anyway, and messing with the video mode may display artifacts,
>> and certainly get into several layers of complexity (including mutexes and
>> memory allocations) which we shall be much safer to avoid.
>
> There's one exception is use printk_delay

OTOH the complexity do exist also when timeout is set, IMHO it is worth

>
>>
>> Signed-off-by: Hugh Dickins <hughd@...gle.com>
>> [ Edited commit message and modified to short-circuit panic_timeout < 0
>>  instead of testing panic_timeout >= 0.  -Mandeep ]
>> Signed-off-by: Mandeep Singh Baines <msb@...omium.org>
>> Cc: Dave Airlie <airlied@...hat.com>
>> Cc: Andrew Morton <akpm@...ux-foundation.org>
>> Cc: dri-devel@...ts.freedesktop.org
>> ---
>>  drivers/gpu/drm/drm_fb_helper.c |    7 +++++++
>>  1 files changed, 7 insertions(+), 0 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
>> index f7c6854..0e62c93 100644
>> --- a/drivers/gpu/drm/drm_fb_helper.c
>> +++ b/drivers/gpu/drm/drm_fb_helper.c
>> @@ -254,6 +254,13 @@ bool drm_fb_helper_force_kernel_mode(void)
>>  int drm_fb_helper_panic(struct notifier_block *n, unsigned long ununsed,
>>                        void *panic_str)
>>  {
>> +       /*
>> +        * It's a waste of time and effort to switch back to text console
>> +        * if the kernel should reboot before panic messages can be seen.
>> +        */
>> +       if (panic_timeout < 0)
>> +               return 0;
>> +
>>        printk(KERN_ERR "panic occurred, switching back to text console\n");
>>        return drm_fb_helper_force_kernel_mode();
>>  }
>> --
>> 1.7.3.1
>>
>> --
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>>
>
>
>
> --
> Regards
> Dave
>



-- 
Regards
Dave
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