On Wed, Mar 11, 2020 at 5:52 PM Ananyev, Konstantin
<[email protected]> wrote:
>
>
>
> > -----Original Message-----
> > From: ZY Qiu <[email protected]>
> > Sent: Thursday, March 5, 2020 4:47 PM
> > To: Thomas Monjalon <[email protected]>; Yigit, Ferruh
> > <[email protected]>; Andrew Rybchenko <[email protected]>
> > Cc: [email protected]; [email protected]; Ananyev, Konstantin
> > <[email protected]>; ZY Qiu
> > <[email protected]>
> > Subject: [PATCH v3] rte_ethdev: safer memory access by calling Rx/Tx
> > callback
> >
> > When compiling with -O0,
> > the compiler does not optimize two memory accesses into one.
> > Leads to accessing a null pointer when queue post Rx burst callback
> > removal while traffic is running.
> >
> > Signed-off-by: ZY Qiu <[email protected]>
> > ---
> > lib/librte_ethdev/rte_ethdev.h | 9 +++++----
> > 1 file changed, 5 insertions(+), 4 deletions(-)
> >
> > diff --git a/lib/librte_ethdev/rte_ethdev.h b/lib/librte_ethdev/rte_ethdev.h
> > index d1a593ad1..c46612e3e 100644
> > --- a/lib/librte_ethdev/rte_ethdev.h
> > +++ b/lib/librte_ethdev/rte_ethdev.h
> > @@ -4388,10 +4388,10 @@ rte_eth_rx_burst(uint16_t port_id, uint16_t
> > queue_id,
> > rx_pkts, nb_pkts);
> >
> > #ifdef RTE_ETHDEV_RXTX_CALLBACKS
> > - if (unlikely(dev->post_rx_burst_cbs[queue_id] != NULL)) {
> > - struct rte_eth_rxtx_callback *cb =
> > - dev->post_rx_burst_cbs[queue_id];
> > + struct rte_eth_rxtx_callback *volatile cb =
> > + dev->post_rx_burst_cbs[queue_id];
I prefer to change to compiler_barrier() if it working as volatile may have a
performance impact on fast-path code.
> >
> > + if (unlikely(cb != NULL)) {
> > do {
> > nb_rx = cb->fn.rx(port_id, queue_id, rx_pkts, nb_rx,
> > nb_pkts, cb->param);
> > @@ -4652,7 +4652,8 @@ rte_eth_tx_burst(uint16_t port_id, uint16_t queue_id,
> > #endif
> >
> > #ifdef RTE_ETHDEV_RXTX_CALLBACKS
> > - struct rte_eth_rxtx_callback *cb = dev->pre_tx_burst_cbs[queue_id];
> > + struct rte_eth_rxtx_callback *volatile cb =
> > + dev->pre_tx_burst_cbs[queue_id];
> >
> > if (unlikely(cb != NULL)) {
> > do {
> > --
>
> Acked-by: Konstantin Ananyev <[email protected]>
>
> > 2.17.1
>
