From: Toke Høiland-Jørgensen Date: Thu, 24 Jun 2021 16:06:02 +0000 (+0200) Subject: marvell: Remove rcu_read_lock() around XDP program invocation X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=959ad7ec066d9a61557ad6aedf77ea9b54c82df0;p=linux.git marvell: Remove rcu_read_lock() around XDP program invocation The mvneta and mvpp2 drivers have 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. This turns out to be harmless because it all happens in a single NAPI poll cycle (and thus under local_bh_disable()), but it makes the rcu_read_lock() misleading. Rather than extend the scope of the rcu_read_lock(), just get rid of it entirely. 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. Signed-off-by: Toke Høiland-Jørgensen Signed-off-by: Daniel Borkmann Cc: Thomas Petazzoni Cc: Russell King Cc: Marcin Wojtas Link: https://lore.kernel.org/bpf/20210624160609.292325-13-toke@redhat.com --- diff --git a/drivers/net/ethernet/marvell/mvneta.c b/drivers/net/ethernet/marvell/mvneta.c index c15ce06427d0f..ada4e26a5492b 100644 --- a/drivers/net/ethernet/marvell/mvneta.c +++ b/drivers/net/ethernet/marvell/mvneta.c @@ -2373,7 +2373,6 @@ static int mvneta_rx_swbm(struct napi_struct *napi, /* Get number of received packets */ rx_todo = mvneta_rxq_busy_desc_num_get(pp, rxq); - rcu_read_lock(); xdp_prog = READ_ONCE(pp->xdp_prog); /* Fairness NAPI loop */ @@ -2451,7 +2450,6 @@ next: xdp_buf.data_hard_start = NULL; sinfo.nr_frags = 0; } - rcu_read_unlock(); if (xdp_buf.data_hard_start) mvneta_xdp_put_buff(pp, rxq, &xdp_buf, &sinfo, -1); diff --git a/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c b/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c index 9bca8c8f9f8d7..c31677527a020 100644 --- a/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c +++ b/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c @@ -3881,8 +3881,6 @@ static int mvpp2_rx(struct mvpp2_port *port, struct napi_struct *napi, int rx_done = 0; u32 xdp_ret = 0; - rcu_read_lock(); - xdp_prog = READ_ONCE(port->xdp_prog); /* Get number of received packets and clamp the to-do */ @@ -4028,8 +4026,6 @@ err_drop_frame: mvpp2_bm_pool_put(port, pool, dma_addr, phys_addr); } - rcu_read_unlock(); - if (xdp_ret & MVPP2_XDP_REDIR) xdp_do_flush_map();