Re: [PATCH 1/1] x86: tsc: avoid system instability in hibernation

["Rafael J. Wysocki" <rjw@rjwysocki.net>]

Hi Eduardo,

On Wednesday, July 25, 2018 8:18:46 PM CEST Eduardo Valentin wrote:
> System instability are seen during resume from hibernation when system
> is under heavy CPU load. This is due to the lack of update of sched
> clock data, and the scheduler would then think that heavy CPU hog
> tasks need more time in CPU, causing the system to freeze
> during the unfreezing of tasks. For example, threaded irqs,
> and kernel processes servicing network interface may be delayed
> for several tens of seconds, causing the system to be unreachable.
> 
> Situation like this can be reported by using lockup detectors
> such as workqueue lockup detectors:
> 
> Message from syslogd@ip-172-31-67-114 at May  7 18:23:21 ...
>  kernel:BUG: workqueue lockup - pool cpus=0 node=0 flags=0x0 nice=0 stuck for 57s!
> 
> Message from syslogd@ip-172-31-67-114 at May  7 18:23:21 ...
>  kernel:BUG: workqueue lockup - pool cpus=1 node=0 flags=0x0 nice=0 stuck for 57s!
> 
> Message from syslogd@ip-172-31-67-114 at May  7 18:23:21 ...
>  kernel:BUG: workqueue lockup - pool cpus=3 node=0 flags=0x1 nice=0 stuck for 57s!
> 
> Message from syslogd@ip-172-31-67-114 at May  7 18:29:06 ...
>  kernel:BUG: workqueue lockup - pool cpus=3 node=0 flags=0x1 nice=0 stuck for 403s!
> 
> The fix for this situation is to mark the sched clock as unstable
> as early as possible in the resume path, leaving it unstable
> for the duration of the resume process. This will force the
> scheduler to attempt to align the sched clock across CPUs using
> the delta with time of day, updating sched clock data. In a post
> hibernation event, we can then mark the sched clock as stable
> again, avoiding unnecessary syncs with time of day on systems
> in which TSC is reliable.
> 
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Ingo Molnar <mingo@redhat.com>
> Cc: "H. Peter Anvin" <hpa@zytor.com>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: Dou Liyang <douly.fnst@cn.fujitsu.com>
> Cc: Len Brown <len.brown@intel.com>
> Cc: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
> Cc: Eduardo Valentin <eduval@amazon.com>
> Cc: "mike.travis@hpe.com" <mike.travis@hpe.com>
> Cc: Rajvi Jingar <rajvi.jingar@intel.com>
> Cc: Pavel Tatashin <pasha.tatashin@oracle.com>
> Cc: Philippe Ombredanne <pombredanne@nexb.com>
> Cc: Kate Stewart <kstewart@linuxfoundation.org>
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Cc: x86@kernel.org
> Cc: linux-kernel@vger.kernel.org
> Signed-off-by: Eduardo Valentin <eduval@amazon.com>

Can you please resend this with a CC to linux-pm?

Cheers,
Rafael