| Message ID | 20210609103326.278782-13-toke@redhat.com |
|---|---|
| State | Superseded |
| Headers | show |
| Series | Clean up and document RCU-based object protection for XDP_REDIRECT | expand |
+Jakub On Wed, Jun 09, 2021 at 12:33:21PM +0200, Toke Høiland-Jørgensen wrote: > The nfp driver has rcu_read_lock()/rcu_read_unlock() pairs around XDP > program invocations. However, the actual lifetime of the objects referred > by the XDP program invocation is longer, all the way through to the call to > xdp_do_flush(), making the scope of the rcu_read_lock() too small. > > While this is not actually an issue for the nfp driver because it doesn't > support XDP_REDIRECT (and thus doesn't call xdp_do_flush()), the > rcu_read_lock() is still unneeded. And With the addition of RCU annotations > to the XDP_REDIRECT map types that take bh execution into account, lockdep > even understands this to be safe, so there's really no reason to keep it > around. > > Cc: Simon Horman <simon.horman@netronome.com> > Cc: oss-drivers@netronome.com > Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com> Reviewed-by: Simon Horman <simon.horman@netronome.com> > --- > drivers/net/ethernet/netronome/nfp/nfp_net_common.c | 2 -- > 1 file changed, 2 deletions(-) > > diff --git a/drivers/net/ethernet/netronome/nfp/nfp_net_common.c b/drivers/net/ethernet/netronome/nfp/nfp_net_common.c > index eeb30680b4dc..5dfa4799c34f 100644 > --- a/drivers/net/ethernet/netronome/nfp/nfp_net_common.c > +++ b/drivers/net/ethernet/netronome/nfp/nfp_net_common.c > @@ -1819,7 +1819,6 @@ static int nfp_net_rx(struct nfp_net_rx_ring *rx_ring, int budget) > struct xdp_buff xdp; > int idx; > > - rcu_read_lock(); > xdp_prog = READ_ONCE(dp->xdp_prog); > true_bufsz = xdp_prog ? PAGE_SIZE : dp->fl_bufsz; > xdp_init_buff(&xdp, PAGE_SIZE - NFP_NET_RX_BUF_HEADROOM, > @@ -2036,7 +2035,6 @@ static int nfp_net_rx(struct nfp_net_rx_ring *rx_ring, int budget) > if (!nfp_net_xdp_complete(tx_ring)) > pkts_polled = budget; > } > - rcu_read_unlock(); > > return pkts_polled; > } > -- > 2.31.1 >
diff --git a/drivers/net/ethernet/netronome/nfp/nfp_net_common.c b/drivers/net/ethernet/netronome/nfp/nfp_net_common.c index eeb30680b4dc..5dfa4799c34f 100644 --- a/drivers/net/ethernet/netronome/nfp/nfp_net_common.c +++ b/drivers/net/ethernet/netronome/nfp/nfp_net_common.c @@ -1819,7 +1819,6 @@ static int nfp_net_rx(struct nfp_net_rx_ring *rx_ring, int budget) struct xdp_buff xdp; int idx; - rcu_read_lock(); xdp_prog = READ_ONCE(dp->xdp_prog); true_bufsz = xdp_prog ? PAGE_SIZE : dp->fl_bufsz; xdp_init_buff(&xdp, PAGE_SIZE - NFP_NET_RX_BUF_HEADROOM, @@ -2036,7 +2035,6 @@ static int nfp_net_rx(struct nfp_net_rx_ring *rx_ring, int budget) if (!nfp_net_xdp_complete(tx_ring)) pkts_polled = budget; } - rcu_read_unlock(); return pkts_polled; }
The nfp driver has rcu_read_lock()/rcu_read_unlock() pairs around XDP program invocations. However, the actual lifetime of the objects referred by the XDP program invocation is longer, all the way through to the call to xdp_do_flush(), making the scope of the rcu_read_lock() too small. While this is not actually an issue for the nfp driver because it doesn't support XDP_REDIRECT (and thus doesn't call xdp_do_flush()), the rcu_read_lock() is still unneeded. And With the addition of RCU annotations to the XDP_REDIRECT map types that take bh execution into account, lockdep even understands this to be safe, so there's really no reason to keep it around. Cc: Simon Horman <simon.horman@netronome.com> Cc: oss-drivers@netronome.com Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com> --- drivers/net/ethernet/netronome/nfp/nfp_net_common.c | 2 -- 1 file changed, 2 deletions(-)