[lxc-devel] [PATCH] fix console deadlocks

Serge Hallyn serge.hallyn at ubuntu.com
Fri Sep 20 20:26:47 UTC 2013


Quoting Dwight Engen (dwight.engen at oracle.com):
> On Fri, 20 Sep 2013 14:48:40 -0500
> Serge Hallyn <serge.hallyn at ubuntu.com> wrote:
> 
> > These might be a bit controversial.  The process lock was held
> > for some long periods of time for tweaking consoles.   These
> > can deadlock with some of lock holds I introduced recently.  I
> > would argue that if two threads are fighting over the console,
> > you're gonna have trouble anyway, and the process locks here
> > weren't saving us from anything.  If we want to do a console
> 
> Are we sure we can walk/modify the lxc_ttys list lockless? I agree

Yeah we do need to lock those.  But I don't think there's a rush for
it.

> threaded console use is "interesting", but I don't think we want list
> corruption. Of course we don't want deadlocks either :)

So which do you think would be better - introduce a lxc_ttys lock
specifically, or introduce a general 'console' mutex which is taken
any time we open a console or edit the lxc_ttys?

-serge




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