Messages in this thread | | | Subject | Re: [PATCH net-next 08/12] ptr_ring: prevent queue load/store tearing | From | Jason Wang <> | Date | Fri, 26 Jan 2018 10:38:12 +0800 |
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On 2018年01月26日 07:36, Michael S. Tsirkin wrote: > In theory compiler could tear queue loads or stores in two. It does not > seem to be happening in practice but it seems easier to convert the > cases where this would be a problem to READ/WRITE_ONCE than worry about > it. > > Signed-off-by: Michael S. Tsirkin <mst@redhat.com> > --- > include/linux/ptr_ring.h | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/include/linux/ptr_ring.h b/include/linux/ptr_ring.h > index 3a19ebd..1883d61 100644 > --- a/include/linux/ptr_ring.h > +++ b/include/linux/ptr_ring.h > @@ -114,7 +114,7 @@ static inline int __ptr_ring_produce(struct ptr_ring *r, void *ptr) > /* Pairs with smp_read_barrier_depends in __ptr_ring_consume. */ > smp_wmb(); > > - r->queue[r->producer++] = ptr; > + WRITE_ONCE(r->queue[r->producer++], ptr); > if (unlikely(r->producer >= r->size)) > r->producer = 0;
You may want WRITE_ONCE() here? And if we just fix the out of bound r->producer, we may just need one WRITE_ONCE().
Thanks
> return 0; > @@ -173,7 +173,7 @@ static inline int ptr_ring_produce_bh(struct ptr_ring *r, void *ptr) > static inline void *__ptr_ring_peek(struct ptr_ring *r) > { > if (likely(r->size)) > - return r->queue[r->consumer_head]; > + return READ_ONCE(r->queue[r->consumer_head]); > return NULL; > } >
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