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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <E1I6YDJ-0001sj-00@dorka.pomaz.szeredi.hu>
Date:	Thu, 05 Jul 2007 22:46:09 +0200
From:	Miklos Szeredi <miklos@...redi.hu>
To:	oliver@...kum.org
CC:	miklos@...redi.hu, pavel@....cz, paulus@...ba.org,
	stern@...land.harvard.edu, johannes@...solutions.net, rjw@...k.pl,
	linux-pm@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
	mjg59@...f.ucam.org, benh@...nel.crashing.org
Subject: Re: [linux-pm] Re: [PATCH] Remove process freezer from suspend to RAM pathway

> > Yes, fuse could handle being frozen there.  However that would only
> > solve part of the problem: an operation waiting for a reply could be
> > holding a VFS mutex and some other task may be blocked on that mutex.
> > 
> > How would you solve freezing those tasks?
> 
> OK, you made me reach for literatur on theoretical computer science.
> 
> IMHO the range of actions a fuse server is inherently limited.
> You must never ever block on a lock one of your clients is holding. In
> this case the limitation is not influenced by the freezer.

Obviously.  But I wasn't about the server trying to acquire a lock
held by a client.  I was talking about a client trying to acquire a
lock held by _another_ client.

If this coincides with the server (or some other task which the server
is depending on) being frozen before the clients, the freezer has a
problem.

> The freezer introduces a further limitation in that the server can freeze
> before the client, which must not be. You can prevent that by freezing
> the servers last.
> 
> In principle you might have dependencies between servers and you won't
> catch that, true. You won't catch servers blocking on IPC, but you are
> balancing on the edge of deadlock with fuse anyway.

Huh?

Miklos
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/