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    SubjectRe: [RC][PATCH -mm] PM: Prevent frozen user mode helpers from failing the freezing of tasks
    Hi!

    > > > Special thanks to Uli Luckas <u.luckas@road.de> for reviewing the previous
    > > > versions of this patch and for very useful comments.
    > > ...
    > > > Reviewed-by: Pavel Machek <pavel@ucw.cz>
    > >
    > > Eh, not sure this header is worth anything. Sometimes I'm lazy and
    > > stop when I see first problem.
    > >
    > > > switch (action) {
    > > > case PM_HIBERNATION_PREPARE:
    > > > case PM_SUSPEND_PREPARE:
    > > > usermodehelper_disabled = 1;
    > > > - return NOTIFY_OK;
    > > > + retval = wait_event_timeout(running_helpers_waitq,
    > > > + atomic_read(&running_helpers) == 0,
    > >
    > > Are you sure here? What happens when atomic variable changes between
    > > the atomic_read and the function call?
    >
    > Er, this is a macro. :-)
    >
    > In fact we rely only on atomic_read(&running_helpers) being still zero after
    > helper_finished() has woken us up, but I think that's acceptable.
    >
    > IOW, if the wait_event_timeout() returns with retval different from zero, this
    > means that atomic_read(&running_helpers) returned zero at one point after
    > we'd set usermodehelper_disabled, which is enough. OTOH, if it doesn't

    Ok, can you write short comment explaining that? /* We have set
    usermodehelper_disabled, so any new usermode helpers are not a problem
    */.

    Pavel
    --
    (english) http://www.livejournal.com/~pavelmachek
    (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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