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

Miklos Szeredi
2007-07-05T08:17:17Z

> > > I have discussed the benefits elsewhere.  As 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.  Those 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