The patch below does not apply to the 4.19-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@xxxxxxxxxxxxxxx>.
Thanks,
Sasha
------------------ original commit in Linus's tree ------------------
>From 622d13694b5f048c01caa7ba548498d9880d4cb0 Mon Sep 17 00:00:00 2001
From: Ong Boon Leong <boon.leong.ong@xxxxxxxxx>
Date: Wed, 31 Mar 2021 21:25:03 +0800
Subject: [PATCH] xdp: fix xdp_return_frame() kernel BUG throw for page_pool
memory model
xdp_return_frame() may be called outside of NAPI context to return
xdpf back to page_pool. xdp_return_frame() calls __xdp_return() with
napi_direct = false. For page_pool memory model, __xdp_return() calls
xdp_return_frame_no_direct() unconditionally and below false negative
kernel BUG throw happened under preempt-rt build:
[ 430.450355] BUG: using smp_processor_id() in preemptible [00000000] code: modprobe/3884
[ 430.451678] caller is __xdp_return+0x1ff/0x2e0
[ 430.452111] CPU: 0 PID: 3884 Comm: modprobe Tainted: G U E 5.12.0-rc2+ #45
Changes in v2:
- This patch fixes the issue by making xdp_return_frame_no_direct() is
only called if napi_direct = true, as recommended for better by
Jesper Dangaard Brouer. Thanks!
Fixes: 2539650fadbf ("xdp: Helpers for disabling napi_direct of xdp_return_frame")
Signed-off-by: Ong Boon Leong <boon.leong.ong@xxxxxxxxx>
Acked-by: Jesper Dangaard Brouer <brouer@xxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
---
net/core/xdp.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/net/core/xdp.c b/net/core/xdp.c
index 05354976c1fc..858276e72c68 100644
--- a/net/core/xdp.c
+++ b/net/core/xdp.c
@@ -350,7 +350,8 @@ static void __xdp_return(void *data, struct xdp_mem_info *mem, bool napi_direct,
/* mem->id is valid, checked in xdp_rxq_info_reg_mem_model() */
xa = rhashtable_lookup(mem_id_ht, &mem->id, mem_id_rht_params);
page = virt_to_head_page(data);
- napi_direct &= !xdp_return_frame_no_direct();
+ if (napi_direct && xdp_return_frame_no_direct())
+ napi_direct = false;
page_pool_put_full_page(xa->page_pool, page, napi_direct);
rcu_read_unlock();
break;
--
2.30.2
