Re: [PATCH]2.6 test1 mm2 user.c race (?)

From: Bill Davidsen (davidsen@tmr.com)
Date: Tue Jul 29 2003 - 21:53:30 EST

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On Mon, 28 Jul 2003, Andrew Morton wrote:

> <ffrederick@prov-liege.be> wrote:
> >
> > + spin_lock(&uidhash_lock);
> > uid_hash_insert(&root_user, uidhashentry(0));
> > + spin_unlock(&uidhash_lock);
>
> This code runs within an initcall, so it is very unlikely that anything
> will race with us here.
>
> But SMP is up, and this code gets dropped out of memory later (the
> out-of-line spinlock code doesn't get dropped though).
>
> So yes, I'd prefer that the locking be there, if only for documentary
> purposes. A /* comment */ which explains why the locking was omitted would
> also be suitabe.

I like the locking better than the comment, I trust the analysis today,
but with SMP and preempt, the lock protects the future (and you may be
missing something even today).

-- bill davidsen <davidsen@tmr.com> CTO, TMR Associates, Inc Doing interesting things with little computers since 1979.

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