linux-kernel - Re: [RFC PATCH] drivers: power: Add watchdog timer to catch drivers which lockup during suspend.

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Date:	Wed, 1 May 2013 09:24:48 -0700
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	Colin Cross <ccross@...roid.com>
Cc:	Pavel Machek <pavel@....cz>,
	Zoran Markovic <zoran.markovic@...aro.org>,
	lkml <linux-kernel@...r.kernel.org>,
	Linux PM list <linux-pm@...r.kernel.org>,
	Benoit Goby <benoit@...roid.com>,
	Android Kernel Team <kernel-team@...roid.com>,
	Todd Poynor <toddpoynor@...gle.com>,
	San Mehat <san@...gle.com>,
	John Stultz <john.stultz@...aro.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>, Len Brown <len.brown@...el.com>
Subject: Re: [RFC PATCH] drivers: power: Add watchdog timer to catch drivers
 which lockup during suspend.

On Wed, May 01, 2013 at 09:10:49AM -0700, Colin Cross wrote:
> I'm not saying this patch as is is right for everyone (it probably at
> least needs to be configurable to be turned off, change the delay, and
> change the panic to just a stack trace),

Those changes would be nice.

> but from a mobile perspective
> this patch is far more debuggable than without this patch.  We work
> very hard to make sure that panic's are highly debuggable, in fact we
> often prefer panics over any other behavior when the device is in a
> bad state, because it immediately gets the user's device working again
> while still giving us useful information in our automatic log
> collection.
> 
> With an mdelay(100000) in the suspend path, users in our debug device
> pool are likely to just pull the battery because their screen won't
> turn on, in which case I get no debugging information.  With this
> patch, the device will automatically reboot due to the panic, and I
> will get captured logs after reboot that show a stack trace ending
> with mdelay, which tells me exactly where to look for this
> mdelay(100000).

All of that information would be _great_ to have in the changelog for
the patch, as it explains exactly why you need this.  {hint}

thanks,

greg k-h
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