linux-kernel - Re: [RFC PATCHv2 2/2] PM: compile-time configuration of device suspend/resume watchdogs.

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Message-ID: <51910EC2.8090501@linaro.org>
Date:	Mon, 13 May 2013 09:03:14 -0700
From:	John Stultz <john.stultz@...aro.org>
To:	Colin Cross <ccross@...roid.com>
CC:	Zoran Markovic <zoran.markovic@...aro.org>,
	lkml <linux-kernel@...r.kernel.org>,
	Linux PM list <linux-pm@...r.kernel.org>,
	Android Kernel Team <kernel-team@...roid.com>,
	Todd Poynor <toddpoynor@...gle.com>,
	San Mehat <san@...gle.com>, Benoit Goby <benoit@...roid.com>,
	Pavel Machek <pavel@....cz>, "Rafael J. Wysocki" <rjw@...k.pl>,
	Len Brown <len.brown@...el.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [RFC PATCHv2 2/2] PM: compile-time configuration of device suspend/resume
 watchdogs.

On 05/10/2013 11:23 PM, Colin Cross wrote:
> On Fri, May 10, 2013 at 2:28 PM, Zoran Markovic
> <zoran.markovic@...aro.org> wrote:
>> +#ifdef CONFIG_DPM_WD
>> +/**
>> + * dpm_wd_action - recovery from suspend/resume watchdog timeout
>> + * @wd: Watchdog. Must be allocated on the stack.
>> + */
>> +#if defined(CONFIG_DPM_WD_ACTION_STACKTRACE)
>> +static inline void dpm_wd_action(struct dpm_watchdog *wd)
>> +{
>> +       show_stack(wd->tsk, NULL);
>> +}
>> +#elif defined(CONFIG_DPM_WD_ACTION_PANIC)
>> +static inline void dpm_wd_action(struct dpm_watchdog *wd)
>> +{
>> +       panic("%s: unrecoverable failure\n", dev_name(wd->dev));
> The panic here is not very useful, it's going to print the stack of
> the task that was running when the timer fired which is likely to be
> the idle task if the suspend task is deadlocked.  This should call
> show_stack and panic.  If you take out the log action, then all this
> can stay inline with the handler and be:
>
> dev_emerg(wd->dev, "**** DPM device timeout ****\n");
> show_stack(wd->tsk, NULL);
> #ifdef CONFIG_DPM_WD_ACTION_PANIC
> panic("%s: unrecoverable failure\n", dev_name(wd->dev));
> #endif

#ifdefs in functions are usually to be avoided. Thus why I suggested he 
use the config dependent dpm_wd_action() function to handle this.

thanks
-john

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