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    SubjectRe: [linux-pm] [PATCH] Remove process freezer from suspend to RAM pathway
    FromMiklos Szeredi <>
    DateThu, 05 Jul 2007 10:37:22 +0200
    > > Pro-freezers say:
    > > 
    > >   - don't remove the freezer, otherwise we'll have to deal with
    > >     numerous problems in drivers
    > 
    > And these problems will generally be difficult to reproduce reliably
    > and debug.
    
    I see exactly the opposite.
    
    With the freezer I can have very rarely occuring failures, due to
    freeze ordering effects.
    
    And without the freezer I have a 100% reproducable problem, that is
    not hard to fix according to Alan Stern.  OK, I don't know what the
    next problem would be, but the powermac experience shows, that it's
    not nearly as bad as you and Oliver try to make it out.
    
    > > Can this be fixed?
    > > 
    > > It seems to be a fundamental problem with the freezer: while it does
    > > make sure that user processes are not calling into drivers during
    > > suspend, it also disallows perfectly harmless non-driver calls as
    > > well.
    > 
    > The problem is that when the freezer was designed (I didn't do that, BTW),
    > there was no FUSE and similar things, so it's not prepared to cope with
    > such interdependencies between user space tasks.
    > 
    > We had an analogous problem with vfork() and it was solved by using the
    > PF_FREEZER_SKIP flag.  Perhaps we can do similar thing with FUSE.
    
    It cannot be just worked around in fuse, as a task might be sleeping
    on a number of VFS mutexes as well (i_mutex, s_vfs_rename_mutex, etc).
    It would be a gigantic hack, possible at all.
    
    Miklos
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