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    SubjectRe: [linux-pm] Re: [PATCH] Remove process freezer from suspend to RAM pathway

    > > > > In which way can user space tasks depend on each other in a way that
    > > > > allows a them members of that cycle to be in uninterruptible sleep?
    > > >
    > > > - process A calls rename() on a fuse fs
    > > > - process B, the fuse server, starts to process the rename request
    > > > - process B is frozen before it can reply
    > > >
    > > > Now process A is unfreezable. We cannot make rename() restartable,
    > > > hence it cannot be interruptible.
    > >
    > > Yes, we are claiming fuse is very special in this regard, and perhaps
    > > even broken.
    > >
    > > Let's see. If I SIGSTOP the fuse server, I can get unrelated tasks
    > > unkillable (even for SIGKILL!) forever.
    > Actually fuse allows SIGKILL, because it's always fatal, and the
    > syscall may not be restarted.

    I think you want to stick try_to_freeze() at the same places where you
    do SIGKILL handling. That should solve the 'syslogd is unfreezeable'

    Plus, it would be nice to find out where suspend/hibernation is
    triggering fuse activity. We can then decide where to fix it -- in
    fuse or in suspend parts. You said sys_sync is not implemented... so
    where is the problem?

    > > That's very special, and maybe even a FUSE bug. And that is also
    > > what makes FUSE special w.r.t. s2ram.
    > What makes fuse special is that some file operations are synchronous
    > and non-restartable. That's just how the UNIX filesystem API works
    > and is hardly a bug in fuse.

    Well, unix is not plan9, and maybe userland filesystems are impossible
    in unix. But that is hardly a bug in unix :-).


    (cesky, pictures)
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