On 07/21, Andrew Morton wrote:
>
> On Sat, 21 Jul 2007 23:11:04 +0400 Oleg Nesterov <[email protected]> wrote:
>
> > On 07/21, Andrew Morton wrote:
> > >
> > > On Sat, 21 Jul 2007 19:02:06 +0400 Oleg Nesterov <[email protected]> wrote:
> > >
> > > > Make sure that spin_unlock_wait() is properly ordered wrt atomic_inc().
> > > >
> > > > Signed-off-by: Oleg Nesterov <[email protected]>
> > > >
> > > > --- t/net/dccp/ccid.c~ccid 2006-12-18 18:17:31.000000000 +0300
> > > > +++ t/net/dccp/ccid.c 2007-07-21 18:29:21.000000000 +0400
> > > > @@ -40,6 +40,7 @@ static inline void ccids_write_unlock(vo
> > > > static inline void ccids_read_lock(void)
> > > > {
> > > > atomic_inc(&ccids_lockct);
> > > > + smp_mb__after_atomic_inc();
> > > > spin_unlock_wait(&ccids_lock);
> > > > }
> > > >
> > >
> > > Why not just use standard rwlocks in there?
> > >
> > > (This is probably an FAQ, but it should be).
> >
> > Perhaps because read_lock() doesn't allow to sleep?
> >
>
> down_read() does.
>
> afaict the code doesn't sleep while holding that lock anwyay.
Ah yes, it doesn't call kmem_cache_alloc() under ccids_read_lock().
So, really, why not read_lock/write_lock ?
Oleg.
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