Re: [RFC][PATCH -mm] PM: Prevent frozen user mode helpers from failing the freezing of tasks

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



Hi!

> From: Rafael J. Wysocki <rjw@xxxxxxx>
> 
> 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@xxxxxxx> 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
_______________________________________________
linux-pm mailing list
linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx
https://lists.linux-foundation.org/mailman/listinfo/linux-pm


[Index of Archives]     [Linux ACPI]     [Netdev]     [Ethernet Bridging]     [Linux Wireless]     [CPU Freq]     [Kernel Newbies]     [Fedora Kernel]     [Security]     [Linux for Hams]     [Netfilter]     [Bugtraq]     [Yosemite News]     [MIPS Linux]     [ARM Linux]     [Linux RAID]     [Linux Admin]     [Samba]

  Powered by Linux