netdev - [PATCH bpf-next] samples/bpf: fix possible hang in xdpsock with multiple threads

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Message-Id: <20201210153645.21286-1-magnus.karlsson@gmail.com>
Date:   Thu, 10 Dec 2020 16:36:45 +0100
From:   Magnus Karlsson <magnus.karlsson@...il.com>
To:     magnus.karlsson@...el.com, bjorn.topel@...el.com, ast@...nel.org,
        daniel@...earbox.net, netdev@...r.kernel.org
Cc:     bpf@...r.kernel.org, jonathan.lemon@...il.com,
        maciej.fijalkowski@...el.com, maciejromanfijalkowski@...il.com
Subject: [PATCH bpf-next] samples/bpf: fix possible hang in xdpsock with multiple threads

From: Magnus Karlsson <magnus.karlsson@...el.com>

Fix a possible hang in xdpsock that can occur when using multiple
threads. In this case, one or more of the threads might get stuck in
the while-loop in tx_only after the user has signaled the main thread
to stop execution. In this case, no more Tx packets will be sent, so a
thread might get stuck in the aforementioned while-loop. Fix this by
introducing a test inside the while-loop to check if the benchmark has
been terminated. If so, exit the loop.

Fixes: cd9e72b6f210 ("samples/bpf: xdpsock: Add option to specify batch size")
Signed-off-by: Magnus Karlsson <magnus.karlsson@...el.com>
---
 samples/bpf/xdpsock_user.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/samples/bpf/xdpsock_user.c b/samples/bpf/xdpsock_user.c
index 568f9815bb1b..813f7eaabf82 100644
--- a/samples/bpf/xdpsock_user.c
+++ b/samples/bpf/xdpsock_user.c
@@ -1275,6 +1275,8 @@ static void tx_only(struct xsk_socket_info *xsk, u32 *frame_nb, int batch_size)
 	while (xsk_ring_prod__reserve(&xsk->tx, batch_size, &idx) <
 				      batch_size) {
 		complete_tx_only(xsk, batch_size);
+		if (benchmark_done)
+			break;
 	}
 
 	for (i = 0; i < batch_size; i++) {

base-commit: 08c6a2f620e427e879d6ec9329143d6fcd810cd8
-- 
2.29.0