2008-01-18 21:51:31

by [email protected]

[permalink] [raw]
Subject: Re: [PATCH 1/4] SUNRPC: spin svc_rqst initialization to its own function

On Fri, Jan 18, 2008 at 04:48:44PM -0500, Jeff Layton wrote:
> On Fri, 18 Jan 2008 15:59:43 -0500
> "J. Bruce Fields" <[email protected]> wrote:
>
> > On Mon, Jan 14, 2008 at 09:05:15AM -0500, Jeff Layton wrote:
> > > Move the initialzation in __svc_create_thread that happens prior to
> > > thread creation to a new function. Export the function to allow
> > > services to have better control over the svc_rqst structs.
> > >
> > > Also rearrange the rqstp initialization to prevent NULL pointer
> > > dereferences in svc_exit_thread in case allocations fail.
> >
> > Those NULL dereferences are from the
> >
> > list_del(&rqstp->rq_all);
> >
> > ? OK, make sense. Thanks!
> >
> > --b.
> >
>
> Sorry, I didn't explain that well...
>
> This was the problem that Neil pointed out with the existing code. If
> the rqstp kzalloc succeeds, but the later kmallocs in
> __svc_create_thread fail, we goto here:
>
> out_thread:
> svc_exit_thread(rqstp);
>
> svc_exit_thread does this:
>
> struct svc_pool *pool = rqstp->rq_pool;
>
> ...and then later:
>
> spin_lock_bh(&pool->sp_lock);
>
> ...but rq_pool is set after the kmallocs, so if they fail rq_pool will
> be NULL, and we'll oops in that spin_lock_bh().
>
> The fix is to move the kmallocs closer to the bottom in the new
> svc_prepare_thread function.

OK, got it, thanks.

--b.