linux-kernel - RE: [PATCH 1/1] PM: Thaws refrigerated and to be exited kernel threads

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Date:	Sun, 8 Nov 2009 09:52:52 +0530
From:	"Dasgupta, Romit" <romit@...com>
To:	Pavel Machek <pavel@....cz>
CC:	"Rafael J. Wysocki" <rjw@...k.pl>,
	"linux-omap@...r.kernel.org" <linux-omap@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-pm@...ts.linux-foundation.org" 
	<linux-pm@...ts.linux-foundation.org>
Subject: RE: [PATCH 1/1] PM: Thaws refrigerated and to be exited kernel
	threads

> Subject: Re: [PATCH 1/1] PM: Thaws refrigerated and to be exited kernel
> threads
> 
> Hi!
> 
> > Kicks out a frozen thread from the refrigerator when an active thread has
> > invoked kthread_stop on the frozen thread.
> >
> > Signed-off-by: Romit Dasgupta <romit@...com>
> > ---
> >
> > diff --git a/kernel/freezer.c b/kernel/freezer.c
> > index bd1d42b..c28dbe8 100644
> > --- a/kernel/freezer.c
> > +++ b/kernel/freezer.c
> > @@ -9,6 +9,7 @@
> >  #include <linux/module.h>
> >  #include <linux/syscalls.h>
> >  #include <linux/freezer.h>
> > +#include <linux/kthread.h>
> >
> >  /*
> >   * freezing is complete, mark current process as frozen
> > @@ -49,7 +50,7 @@ void refrigerator(void)
> >
> >  	for (;;) {
> >  		set_current_state(TASK_UNINTERRUPTIBLE);
> > -		if (!frozen(current))
> > +		if (!frozen(current) || (!current->mm && kthread_should_stop()))
> >  			break;
> >  		schedule();
> 
> Well, what if the thread does some processing before stopping? That
> would break refrigerator assumptions...

The suspend thread will block until the 'to be stopped' thread clears up. That is what any call to kthread_stop would boil down to. The target thread would anyway be out of the refrigerator so I am not sure what assumption you mean here. Eventually, the target thread would clear up and wake up the suspend thread and then things would go on as usual.
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