lkml.org 
[lkml]   [2007]   [Jul]   [7]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
SubjectRe: [RFC][PATCH -mm] Freezer: Handle uninterruptible tasks
Date
Hi.

On Saturday 07 July 2007 17:50:18 Pavel Machek wrote:
> Hi!
>
> > The main limitation of the freezer is that it cannot handle
uninterruptible
> > tasks. Namely, if there are uninterruptible tasks in the system, the
freezer
> > returns an error, which makes it impossible to suspend the system.
> ...
> > Unfortunately, this mechanism also leads to severe limitations, such as
that it
> > makes the freezer unable to handle systems using FUSE in a reliable way.
> >
> > This patch makes the freezer skip uninterruptible user space tasks (ie.
such
> > that have an mm of their own) when counting the tasks to be frozen. As a
> > result, these tasks have the TIF_FREEZE and TIF_SIGPENDING flags set, but
the
> > freezer doesn't wait for them to enter the refrigerator. Nevertheless,
they
> > will enter the refrigerator as soon as they change their state.
>
> I don't think we can do that. I suspect rename looks like:
>
> write directory entry in source
> A) (uninterruptible wait for write)
> write directory entry in destination
> (uninterruptible wait for write)
> write something else
>
> If we freeze some task in place "A)", we'll write to the disk when the
> directory write is finished :-(.

Renaming is a single syscall, so won't the process get frozen when the syscall
finishes? The sys_sync will also help here - it will ensure the rename gets
flushed before we start on freezing kernel threads.

Perhaps you've just found more logic for keeping the sys_sync there?

Regards,

Nigel
--
See http://www.tuxonice.net for Howtos, FAQs, mailing
lists, wiki and bugzilla info.
[unhandled content-type:application/pgp-signature]
\
 
 \ /
  Last update: 2007-07-07 11:17    [W:3.080 / U:1.292 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site