Messages in this thread Patch in this message | | | Date | Wed, 24 Jun 2009 18:30:24 +0200 | From | Oleg Nesterov <> | Subject | Re: [RFC] tcp: race in receive part |
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On 06/24, Jiri Olsa wrote: > > +/* The read_lock() on x86 is a full memory barrier. */ > +#define smp_mb__after_read_lock() barrier()
Just curious, why do we need barrier() ?
I must admit, personally I dislike _read_lock part. Because I think we need a "more generic" smp_mb__{before,after}_lock() or whatever which work for spin_lock/read_lock/write_lock.
In that case it can have more users. Btw, in fs/select.c too, see __pollwake().
And surprise,
> --- a/fs/select.c > +++ b/fs/select.c > @@ -219,6 +219,10 @@ static void __pollwait(struct file *filp, wait_queue_head_t *wait_address, > init_waitqueue_func_entry(&entry->wait, pollwake); > entry->wait.private = pwq; > add_wait_queue(wait_address, &entry->wait); > + > + /* This memory barrier is paired with the smp_mb__after_read_lock > + * in the sk_has_sleeper. */ > + smp_mb();
This could be smp_mb__after_lock() too.
Oleg.
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