lkml.org 
[lkml]   [2007]   [Jun]   [21]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [RFC][PATCH -mm] PM: Prevent frozen user mode helpers from failing the freezing of tasks
Hi!

> From: Rafael J. Wysocki <rjw@sisk.pl>
>
> At present, if a user mode helper is running while usermodehelper_pm_callback()
> is executed, the helper may be frozen and the completion in
> call_usermodehelper_exec() won't be completed until user space processes are
> thawed. As a result, the freezing of kernel threads may fail, which is not
> desirable.
>
> Prevent this from happening by introducing a counter of running user mode
> helpers and allowing usermodehelper_pm_callback() to succeed for
> action = PM_HIBERNATION_PREPARE or action = PM_SUSPEND_PREPARE only if there
> are no helpers running. [Namely, usermodehelper_pm_callback() waits for at most
> RUNNING_HELPERS_TIMEOUT for the number of running helpers to become zero and
> fails if that doesn't happen.]
>
> Special thanks to Uli Luckas <u.luckas@road.de> for reviewing the previous
> versions of this patch and for very useful comments.
>

> - return NOTIFY_OK;
> + wait_event_timeout(running_helpers_waitq,
> + atomic_read(&running_helpers) == 0,
> + RUNNING_HELPERS_TIMEOUT);
> + if (atomic_read(&running_helpers) == 0) {

Uff, this is suspect. What happens if running_helpers goes to 1 here.?

> + return NOTIFY_OK;


Pavel
--
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2007-06-21 15:33    [W:0.109 / U:0.128 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site