diff mbox series

[net,04/11] net/mlx5e: Wrap mlx5e_trap_napi_poll into rcu_read_lock

Message ID 20220518063427.123758-5-saeed@kernel.org (mailing list archive)
State Accepted
Commit 379169740b0a955972cebb4994b2607b264a4b41
Delegated to: Netdev Maintainers
Headers show
Series [net,01/11] net/mlx5: DR, Fix missing flow_source when creating multi-destination FW table | expand

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Context Check Description
netdev/tree_selection success Clearly marked for net
netdev/fixes_present success Fixes tag present in non-next series
netdev/subject_prefix success Link
netdev/cover_letter success Pull request is its own cover letter
netdev/patch_count success Link
netdev/header_inline success No static functions without inline keyword in header files
netdev/build_32bit success Errors and warnings before: 0 this patch: 0
netdev/cc_maintainers warning 1 maintainers not CCed: edumazet@google.com
netdev/build_clang success Errors and warnings before: 0 this patch: 0
netdev/module_param success Was 0 now: 0
netdev/verify_signedoff success Signed-off-by tag matches author and committer
netdev/verify_fixes success Fixes tag looks correct
netdev/build_allmodconfig_warn success Errors and warnings before: 0 this patch: 0
netdev/checkpatch success total: 0 errors, 0 warnings, 0 checks, 29 lines checked
netdev/kdoc success Errors and warnings before: 0 this patch: 0
netdev/source_inline success Was 0 now: 0

Commit Message

Saeed Mahameed May 18, 2022, 6:34 a.m. UTC 
From: Maxim Mikityanskiy <maximmi@nvidia.com>

The body of mlx5e_napi_poll is wrapped into rcu_read_lock to be able to
read the XDP program pointer using rcu_dereference. However, the trap RQ
NAPI doesn't use rcu_read_lock, because the trap RQ works only in the
non-linear mode, and mlx5e_skb_from_cqe_nonlinear, until recently,
didn't support XDP and didn't call rcu_dereference.

Starting from the cited commit, mlx5e_skb_from_cqe_nonlinear supports
XDP and calls rcu_dereference, but mlx5e_trap_napi_poll doesn't wrap it
into rcu_read_lock. It leads to RCU-lockdep warnings like this:

    WARNING: suspicious RCU usage

This commit fixes the issue by adding an rcu_read_lock to
mlx5e_trap_napi_poll, similarly to mlx5e_napi_poll.

Fixes: ea5d49bdae8b ("net/mlx5e: Add XDP multi buffer support to the non-linear legacy RQ")
Signed-off-by: Maxim Mikityanskiy <maximmi@nvidia.com>
Reviewed-by: Tariq Toukan <tariqt@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>
---
 drivers/net/ethernet/mellanox/mlx5/core/en/trap.c | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)
diff mbox series

Patch

diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en/trap.c b/drivers/net/ethernet/mellanox/mlx5/core/en/trap.c
index a55b066746cb..857840ab1e91 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/en/trap.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en/trap.c
@@ -14,19 +14,26 @@  static int mlx5e_trap_napi_poll(struct napi_struct *napi, int budget)
 	bool busy = false;
 	int work_done = 0;
 
+	rcu_read_lock();
+
 	ch_stats->poll++;
 
 	work_done = mlx5e_poll_rx_cq(&rq->cq, budget);
 	busy |= work_done == budget;
 	busy |= rq->post_wqes(rq);
 
-	if (busy)
-		return budget;
+	if (busy) {
+		work_done = budget;
+		goto out;
+	}
 
 	if (unlikely(!napi_complete_done(napi, work_done)))
-		return work_done;
+		goto out;
 
 	mlx5e_cq_arm(&rq->cq);
+
+out:
+	rcu_read_unlock();
 	return work_done;
 }