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

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Date:	Sat, 07 Jul 2007 22:14:34 +0200
From:	Miklos Szeredi <miklos@...redi.hu>
To:	pavel@....cz
CC:	miklos@...redi.hu, rjw@...k.pl, mjg59@...f.ucam.org,
	paulus@...ba.org, stern@...land.harvard.edu,
	johannes@...solutions.net, linux-pm@...ts.linux-foundation.org,
	linux-kernel@...r.kernel.org
Subject: Re: removing refrigerator does not help with s2ram vs. fuse deadlocks (was Re: [linux-pm] Re: [PATCH] Remove process freezer from suspend to RAM pathway)

> > One task doing ptrace() can basically do whatever it wants with the
> > task being traced.  This is not an exact analogy to what fuse does,
> > but close.
> 
> Well, IMO userland tasks should not have power to grab VFS mutexes for
> indefinite ammount of time. ("fused is allowed to deadlock kernel, in
> a way only write to special file helps" is ugly). Unfortunately, I
> don't think there's a way to work around that deadlock within fuse
> design limits... (coda was able to get around it by working on whole
> files granularity, AFAICT), so we'll have to live with that.

That's just file I/O.  You can easily deadlock coda with any other
file operation.  In fact coda is _less_ robust wrt a misbehaving
userspace server than fuse by a big margin.

Miklos
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