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

[Miklos Szeredi]

> > > I have discussed the benefits elsewhere. ÂAs for the deadlocks -- do 
> > > you still observe them if you use the version of the freezer which 
> > > doesn't freeze kernel threads?
> > 
> > In general the only way to guarantee there are no deadlocks is to
> > construct the graph of dependencies between tasks. ÂThose dependencies
> > are not in practice observable from outside the tasks, so it is
> > virtually impossible to construct the graph.
> 
> 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.

Miklos
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