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    SubjectRe: [PATCH] firmware loader: don't cancel _nowait requests when helper is not yet available
    On Wednesday, March 14, 2012, Stephen Boyd wrote:
    > On 03/13/12 13:14, Rafael J. Wysocki wrote:
    > > All of those use cases are in fact of the "wait for user space to be thawed
    > > and then load the firmware" type, which I believe may be handled without
    > > changing that code.
    > >
    > > Why don't you make your kthread freezable, for one example?
    > >
    > > Why don't you use a freezable workqueue instead?
    > >
    > If we put it on the freezable workqueue or make it a freezable thread
    > will it work?

    That depends on what exactly you want to achieve, which isn't entirely clear
    to me at this point.

    > In my scenario a wakeup interrupt comes in that wakes us up from
    > suspend. Within that wakeup handler a work item is scheduled to the
    > freezable workqueue. That work item then calls request_firmware().

    That should work.

    > It looks like we call schedule() after thawing the workqueues and tasks
    > so the work item could run before usermodehelpers are enabled and then
    > request_firmware() would fail. Do we need something like this (ignore
    > the fact that we call usermodhelper_enable() twice)?
    > diff --git a/kernel/power/process.c b/kernel/power/process.c
    > index 7e42645..61bfa95 100644
    > --- a/kernel/power/process.c
    > +++ b/kernel/power/process.c
    > @@ -187,6 +187,7 @@ void thaw_processes(void)
    > } while_each_thread(g, p);
    > read_unlock(&tasklist_lock);
    > + usermodehelper_enable();

    That would be a reasonable change.

    > schedule();
    > printk("done.\n");
    > }
    > Is there a reason we disable usermodehelpers if

    Not really, but CONFIG_SUSPEND_FREEZER=n can only work reliably in a
    very limited set of cases, so I don't think it's even worth making the
    general code depend on it.

    I'd actually prefer to remove CONFIG_SUSPEND_FREEZER altogether,
    because it's not very useful nowadays (probably isn't useful at all).

    > Should we do this instead so that
    > usermodehelpers are only disabled if we freeze userspace? Also what is
    > that schedule() call in thaw_kernel_threads() for? It looks like we'll
    > call schedule between kernel thread thawing and userspace thawing.

    Which is OK, I think.

    > I pushed out the schedule() call to the callers so that we don't call
    > schedule() until userspace is thawed.

    Why did you do that?


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