From: Nigel Cunningham <nigel@suspend2.net>
Organization: Suspend2.net
To: "Rafael J. Wysocki" <rjw@sisk.pl>
Subject: Re: [ 06/23] [Suspend2] Disable usermode helper invocations when the freezer is on.
Date: Tue, 31 Jan 2006 13:24:34 +1000
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Cc: Pavel Machek <pavel@suse.cz>, linux-kernel@vger.kernel.org
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Hi.

On Tuesday 31 January 2006 08:05, Rafael J. Wysocki wrote:
> Hi,
>
> On Thursday 26 January 2006 04:45, Nigel Cunningham wrote:
> > Disable usermode helper invocations when the freezer is on. This avoids
> > deadlocks due to hotplug events occuring while processes are frozen.
> >
> > Signed-off-by: Nigel Cunningham <nigel@suspend2.net>
> >
> >  kernel/kmod.c |    4 ++++
> >  1 files changed, 4 insertions(+), 0 deletions(-)
> >
> > diff --git a/kernel/kmod.c b/kernel/kmod.c
> > index 51a8920..12afa2c 100644
> > --- a/kernel/kmod.c
> > +++ b/kernel/kmod.c
> > @@ -36,6 +36,7 @@
> >  #include <linux/mount.h>
> >  #include <linux/kernel.h>
> >  #include <linux/init.h>
> > +#include <linux/freezer.h>
> >  #include <asm/uaccess.h>
> >
> >  extern int max_threads;
> > @@ -249,6 +250,9 @@ int call_usermodehelper_keys(char *path,
> >  	if (!khelper_wq)
> >  		return -EBUSY;
> >
> > +	if (freezer_is_on())
> > +		return 0;
> > +
> >  	if (path[0] =3D=3D '\0')
> >  		return 0;
>
> Disabling the usermode helper while freeze_processes() is executed seems =
to
> be a good idea to me, but I think it should be done with a mutex or
> something like that.

With the refrigerator code you guys are using at the moment, ouldn't that=20
result in deadlocks when we later try to freeze the process in preparation=
=20
for the atomic restore? (Or perhaps you don't freeze processes at that=20
point?)

Regards,

Nigel

> Greetings,
> Rafael
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=2D-=20
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