From d917c217b612971ea05ae1582e8740b747e0e7e8 Mon Sep 17 00:00:00 2001 From: Sebastian Andrzej Siewior Date: Tue, 4 Nov 2025 16:34:35 +0100 Subject: [PATCH] net: gro_cells: Reduce lock scope in gro_cell_poll One GRO-cell device's NAPI callback can nest into the GRO-cell of another device if the underlying device is also using GRO-cell. This is the case for IPsec over vxlan. These two GRO-cells are separate devices. From lockdep's point of view it is the same because each device is sharing the same lock class and so it reports a possible deadlock assuming one device is nesting into itself. Hold the bh_lock only while accessing gro_cell::napi_skbs in gro_cell_poll(). This reduces the locking scope and avoids acquiring the same lock class multiple times. Fixes: 25718fdcbdd2 ("net: gro_cells: Use nested-BH locking for gro_cell") Reported-by: Gal Pressman Closes: https://lore.kernel.org/all/66664116-edb8-48dc-ad72-d5223696dd19@nvidia.com/ Signed-off-by: Sebastian Andrzej Siewior Link: https://patch.msgid.link/20251104153435.ty88xDQt@linutronix.de Signed-off-by: Jakub Kicinski --- net/core/gro_cells.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/net/core/gro_cells.c b/net/core/gro_cells.c index fd57b845de33..a725d21159a6 100644 --- a/net/core/gro_cells.c +++ b/net/core/gro_cells.c @@ -60,9 +60,10 @@ static int gro_cell_poll(struct napi_struct *napi, int budget) struct sk_buff *skb; int work_done = 0; - __local_lock_nested_bh(&cell->bh_lock); while (work_done < budget) { + __local_lock_nested_bh(&cell->bh_lock); skb = __skb_dequeue(&cell->napi_skbs); + __local_unlock_nested_bh(&cell->bh_lock); if (!skb) break; napi_gro_receive(napi, skb); @@ -71,7 +72,6 @@ static int gro_cell_poll(struct napi_struct *napi, int budget) if (work_done < budget) napi_complete_done(napi, work_done); - __local_unlock_nested_bh(&cell->bh_lock); return work_done; } -- 2.47.3