From: Toke Høiland-Jørgensen Date: Thu, 24 Jun 2021 16:06:09 +0000 (+0200) Subject: ti: Remove rcu_read_lock() around XDP program invocation X-Git-Tag: v5.15~843^2~14^2~5 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=0cc84b9a6003fa7f6ef5d19e7c8532a01cd41776;p=platform%2Fkernel%2Flinux-starfive.git ti: Remove rcu_read_lock() around XDP program invocation The cpsw 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. 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 Tested-by: Grygorii Strashko Reviewed-by: Grygorii Strashko Cc: linux-omap@vger.kernel.org Link: https://lore.kernel.org/bpf/20210624160609.292325-20-toke@redhat.com --- diff --git a/drivers/net/ethernet/ti/cpsw_priv.c b/drivers/net/ethernet/ti/cpsw_priv.c index 5862f0a..ecc2a6b 100644 --- a/drivers/net/ethernet/ti/cpsw_priv.c +++ b/drivers/net/ethernet/ti/cpsw_priv.c @@ -1328,13 +1328,9 @@ int cpsw_run_xdp(struct cpsw_priv *priv, int ch, struct xdp_buff *xdp, struct bpf_prog *prog; u32 act; - rcu_read_lock(); - prog = READ_ONCE(priv->xdp_prog); - if (!prog) { - ret = CPSW_XDP_PASS; - goto out; - } + if (!prog) + return CPSW_XDP_PASS; act = bpf_prog_run_xdp(prog, xdp); /* XDP prog might have changed packet data and boundaries */ @@ -1378,10 +1374,8 @@ int cpsw_run_xdp(struct cpsw_priv *priv, int ch, struct xdp_buff *xdp, ndev->stats.rx_bytes += *len; ndev->stats.rx_packets++; out: - rcu_read_unlock(); return ret; drop: - rcu_read_unlock(); page_pool_recycle_direct(cpsw->page_pool[ch], page); return ret; }