Solution to various issues on resume resulting from WARN_ON in suspend_test_finish() ?

[Stefan Bader]

TJ wrote:
> On Fri, 2009-02-27 at 15:19 +0100, Stefan Bader wrote:
>> This is something that we should consider. It a bit of a nutshell. 5s can feel 
>> long already when returning from suspend. On the other hand is this showing up 
>> as a crash a bit overreacting. Do you have an overview what the most common or 
>> maximum time would be? Another possible solution would be to replace that WARN 
>> by a simple printk(WARN, ...).
> 
> The reason I didn't suggest a printk is the commentary in
> kernel/power/main.c::suspend_test_finish():
> 
> 	 * Warning on either suspend or resume also means the system
> 	 * has some performance issues.  The stack dump of a WARN_ON
> 	 * is more likely to get the right attention than a printk...
> 	 */
> 

Right, I saw that as well. There clearly was an intention behind and at the 
same time I think, if the resume time is much longer than 5-10s people don't 
need a stacktrace to file bugs. ;-) But right, if it turns out that we prevent 
most cases by just increasing the timeout this would eb worth doing.

> I've posted a bit of shell script to a couple of bug reports so far that
> will help gather information on the typical resume times.
> 
> Maybe other dev's could use this in bug reports you are looking at to
> request information so we can make a determination?
> 

To be honest I haven't been looking at those specific set of bugs too much. 
There are lots of others. :-/ That said, all info that you can help us to 
gather is very much appreciated.

> for log in /var/log/kern.log*; do CMD="cat "; echo $log; \
>  [ ! ${log##*.gz} ] && CMD="zcat "; \
>  $CMD $log | grep -n 'PM: \(suspend\|resume\) devices took'; done
> 
> Example output:
> 
> var/log/kern.log
> /var/log/kern.log.0
> 3678:Feb 19 06:06:56 hephaestion kernel: [60285.296215] PM: suspend devices took 3.752 seconds
> 3830:Feb 19 06:06:57 hephaestion kernel: [60354.780958] PM: resume devices took 69.072 seconds
> 3948:Feb 19 10:19:23 hephaestion kernel: [75478.752211] PM: suspend devices took 3.752 seconds
> 4102:Feb 19 10:19:23 hephaestion kernel: [75488.172580] PM: resume devices took 9.024 seconds
> /var/log/kern.log.1.gz
> /var/log/kern.log.2.gz
> /var/log/kern.log.3.gz
> 
> The resume of 69 seconds shows this system is affected by bug #331415
> 
> 
> 


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