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

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Date:	Tue, 12 Jul 2016 14:52:43 +0200
From:	Petr Mladek <pmladek@...e.com>
To:	Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
Cc:	Viresh Kumar <viresh.kumar@...aro.org>, Jan Kara <jack@...e.cz>,
	Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
	Tejun Heo <tj@...nel.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	vlevenetz@...sol.com, vaibhav.hiremath@...aro.org,
	alex.elder@...aro.org, johan@...nel.org, akpm@...ux-foundation.org,
	rostedt@...dmis.org
Subject: Re: [Query] Preemption (hogging) of the work handler

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,
Petr