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    Subjectremoving refrigerator does not help with s2ram vs. fuse deadlocks (was Re: [linux-pm] Re: [PATCH] Remove process freezer from suspend to RAM pathway)
    Hi!

    > > The fact remains that lots of drivers would still need to be changed.
    > > In the read and write methods someone would have to add code amounting
    > > to this:
    > >
    > > if (suspend_is_under_way()) {
    > > mutex_unlock(...);
    > > block_until_resume();
    > > goto restart;
    > > }
    > >
    > > Freezing userspace is a small amount of code by comparison.
    >
    > Normally devices have some sort of queue of pending operations. So
    > all that is required on suspend is to stop processing the queue and
    > wait for any currently-underway operations to complete. The blocking
    > then happens naturally using the normal I/O wait mechanisms.

    So... instead of one big freezer (we know it is problematic), you have
    100 small freezers, problematic in same way :-(.

    Let's take current FUSE problems, and see if they have problem on PPC,
    ok?

    Let's say FUSE thread touches one of those "blocking" devices. It is
    now in D state, somewhere in kernel.... exactly same way refrigerator
    works.

    Now, if kernel needs FUSE services for some reason (that's the problem
    we hit in s2ram case, right?), we have a deadlock.

    So main problem still seems to be "kernel should not depend on
    userland services during suspend", refrigerator or not.
    Pavel
    --
    (english) http://www.livejournal.com/~pavelmachek
    (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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