Re: [Query] Preemption (hogging) of the work handler

From: Petr Mladek
Date: Tue Jul 12 2016 - 08:52:52 EST

On Tue 2016-07-12 18:38:05, Sergey Senozhatsky wrote:
> Hello,
> On (07/11/16 15:35), Viresh Kumar wrote:
> [..]
> > Sometimes, the platform doesn't come back after suspend. I have tried
> > enabling no-console-suspend and the last line it prints is:
> >
> > Disabling non-boot CPUs

I guess that the printk() kthread is not longer scheduled when there
is only one CPU left.

> > And nothing after that at all. We have to forcefully reboot the phone
> > after that. Moving the prints to they synchronous way (using
> > echo 1 > /sys/module/printk/parameters/synchronous), fixes that issue.
> hm... I'll take a look.

We might try to explicitly flush the consoles in suspend_console().
But I am not sure if we always want to do so because it might take
a while. Also it need not help if someone already owns the
console_sem. Note the console_unlock() calls the cond_resched()
when in safe context.

Well, we might do the best effort when no_console_suspend is enabled.

Best Regards,