linux-kernel - Re: [BUG] 3.7-rc regression bisected: s2disk fails to resume image: Processes could not be frozen, cannot continue resuming

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Message-Id: <20130918224032.84e09e0c1372dbc51c86ab1e@gmail.com>
Date:	Wed, 18 Sep 2013 22:40:32 +0400
From:	Andrew Savchenko <bircoph@...il.com>
To:	Al Viro <viro@...IV.linux.org.uk>
Cc:	linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
	suspend-devel@...ts.sourceforge.net
Subject: Re: [BUG] 3.7-rc regression bisected: s2disk fails to resume image:
 Processes could not be frozen, cannot continue resuming

Hello,

On Wed, 18 Sep 2013 14:52:39 +0100 Al Viro wrote:
> On Tue, Aug 27, 2013 at 07:48:43AM +0400, Andrew Savchenko wrote:
> > > Additional (but probably useless) information on this bug may be found
> > > here: https://forums.gentoo.org/viewtopic-p-7371120.html
> 
> Something's very fishy there:
> 
> [quote]
> Digging into suspend-utils code shows that the following ioctl fails on      
> "/dev/snapshot":                                                             
>                                                                                 
>                                     Code:                                       
>                           ioctl(dev, _IO(3, 1), 0);                          
> [end quote]
> 
> but that's _not_ anything freeze-related - that's HDIO_GETGEO, and with zero
> as last argument it will fail, no matter what.  With EFAULT, if nothing
> else...
> 
> Which ioctl() it really is?  A bit further down you write "I modified suspend
> code to see errno, so freeze on /dev/snapshot fails [with EAGAIN]", so you
> have isolated the call in question.  Could you quote the actual code?

Actual code is from suspend-utils tree, swsusp.h:

static inline int freeze(int dev)
{
        return ioctl(dev, SNAPSHOT_FREEZE, 0);
}

And from suspend_ioctls.h:
#define SNAPSHOT_IOC_MAGIC      '3'
#define SNAPSHOT_FREEZE                 _IO(SNAPSHOT_IOC_MAGIC, 1)

My mistake, should be '3' instead of 3.

Best regards,
Andrew Savchenko

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