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From: Tom Li <tomli@tomli.me>
To: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Jani Nikula <jani.nikula@linux.intel.com>,
	Linux Fbdev development list <linux-fbdev@vger.kernel.org>,
	DRI Development <dri-devel@lists.freedesktop.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>,
	Sudip Mukherjee <sudipm.mukherjee@gmail.com>,
	Teddy Wang <teddy.wang@siliconmotion.com>
Subject: Re: Is it possible to reset graphics controller on reboot in a framebuffer driver?
Date: Tue, 12 Mar 2019 17:19:32 +0800	[thread overview]
Message-ID: <20190312091932.GA17859@localhost.localdomain> (raw)
In-Reply-To: <20190308103536.GA17258@localhost.localdomain>

On Fri, Mar 08, 2019 at 06:35:36PM +0800, Tom Li wrote:
> On Fri, Mar 08, 2019 at 10:13:58AM +0100, Geert Uytterhoeven wrote:
> > On Thu, Mar 7, 2019 at 10:38 PM Tom Li <tomli@tomli.me> wrote:
> > > Nevertheless, does it mean there's no way to prevent it from happening if the
> > > user issues a emergency reboot? Like an automatic reboot after a kernel panic,
> > > or a SysRq-B reboot.
> > 
> > If Linux performs a reboot, it calls the shutdown handlers.
> > I think that includes reboot on panic, or SysRq-B, but I'd have to check to
> > be 100% sure.
> 
> Okay, glad to hear that. If it works for SysRq-B or panic reboot, I think
> it would be enough. After all, hard kernel crashes are rare nowadays, and
> most crashes are hard lockups. In case it happens, the user just presses
> the power button to halt.

As I suspected, emergency reboot via SysRq-B is a hard reboot and none of the
reboot handler will be called. I've put a for (;;) {} loop in .shutdown(), the
kernel would hang during a normal reboot, but a SysRq-B reboot will reset the
machine immediately.

Fortunately, I've found a way to stop trigger the bug in the driver, so no
shutdown handler is needed anymore.

Cheers,
Tom Li

WARNING: multiple messages have this Message-ID

From: Tom Li <tomli@tomli.me>
To: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Jani Nikula <jani.nikula@linux.intel.com>,
	Linux Fbdev development list <linux-fbdev@vger.kernel.org>,
	DRI Development <dri-devel@lists.freedesktop.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>,
	Sudip Mukherjee <sudipm.mukherjee@gmail.com>,
	Teddy Wang <teddy.wang@siliconmotion.com>
Subject: Re: Is it possible to reset graphics controller on reboot in a framebuffer driver?
Date: Tue, 12 Mar 2019 09:19:32 +0000	[thread overview]
Message-ID: <20190312091932.GA17859@localhost.localdomain> (raw)
In-Reply-To: <20190308103536.GA17258@localhost.localdomain>

On Fri, Mar 08, 2019 at 06:35:36PM +0800, Tom Li wrote:
> On Fri, Mar 08, 2019 at 10:13:58AM +0100, Geert Uytterhoeven wrote:
> > On Thu, Mar 7, 2019 at 10:38 PM Tom Li <tomli@tomli.me> wrote:
> > > Nevertheless, does it mean there's no way to prevent it from happening if the
> > > user issues a emergency reboot? Like an automatic reboot after a kernel panic,
> > > or a SysRq-B reboot.
> > 
> > If Linux performs a reboot, it calls the shutdown handlers.
> > I think that includes reboot on panic, or SysRq-B, but I'd have to check to
> > be 100% sure.
> 
> Okay, glad to hear that. If it works for SysRq-B or panic reboot, I think
> it would be enough. After all, hard kernel crashes are rare nowadays, and
> most crashes are hard lockups. In case it happens, the user just presses
> the power button to halt.

As I suspected, emergency reboot via SysRq-B is a hard reboot and none of the
reboot handler will be called. I've put a for (;;) {} loop in .shutdown(), the
kernel would hang during a normal reboot, but a SysRq-B reboot will reset the
machine immediately.

Fortunately, I've found a way to stop trigger the bug in the driver, so no
shutdown handler is needed anymore.

Cheers,
Tom Li

  reply	other threads:[~2019-03-12  9:19 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-03-07  5:16 Is it possible to reset graphics controller on reboot in a framebuffer driver? Tom Li
2019-03-07  5:16 ` Tom Li
2019-03-07  8:58 ` Jani Nikula
2019-03-07  9:00   ` Jani Nikula
2019-03-07  9:00   ` Jani Nikula
2019-03-07  9:39   ` Geert Uytterhoeven
2019-03-07  9:39     ` Geert Uytterhoeven
2019-03-07  9:39     ` Geert Uytterhoeven
2019-03-07 21:38     ` Tom Li
2019-03-07 21:38       ` Tom Li
2019-03-08  9:13       ` Geert Uytterhoeven
2019-03-08  9:13         ` Geert Uytterhoeven
2019-03-08 10:35         ` Tom Li
2019-03-08 10:35           ` Tom Li
2019-03-12  9:19           ` Tom Li [this message]
2019-03-12  9:19             ` Tom Li

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