Messages in this thread | | | Date | Thu, 21 Jun 2007 15:30:15 +0200 | From | Pavel Machek <> | Subject | Re: [RFC][PATCH -mm] PM: Prevent frozen user mode helpers from failing the freezing of tasks |
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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/
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