linux-kernel - Re: [PATCH] Fix initialization of runqueues

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Date:	Thu, 3 Aug 2006 20:26:34 +0200
From:	Samuel Thibault <samuel.thibault@...-lyon.org>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	Ingo Molnar <mingo@...e.hu>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Fix initialization of runqueues

Steven Rostedt, le Thu 03 Aug 2006 11:07:37 -0400, a écrit :
> On Wed, 2006-08-02 at 18:57 +0200, Samuel Thibault wrote:
> > Ingo Molnar, le Wed 02 Aug 2006 17:24:19 +0200, a écrit :
> > > 
> > > * Samuel Thibault <samuel.thibault@...-lyon.org> wrote:
> > > 
> > > > Hi,
> > > > 
> > > > There's an odd thing about the nr_active field in arrays of 
> > > > runqueue_t: it is actually never initialized to 0!...  This doesn't 
> > > > yet trigger a bug probably because the way runqueues are allocated 
> > > > make it so that it is already initialized to 0, but that's not a safe 
> > > > way.  Here is a patch:
> > > 
> > > we do rely on zero initialization of bss (and percpu) data in a number 
> > > of places.
> > 
> > The rest of runqueue initialization doesn't rely on that, and as
> > a result people might think that it is safe to allocate runqueues
> > dynamically.
> 
> I don't buy the "safe to allocate runqueues dynamically" bit since they
> are local to sched.c and if you do do that (I did for a customer once)
> you better know what you're doing.

Yes, but as you agreed, initializing some members to 0 and not others
doesn't help to know what you're doing :)

Samuel
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