linux-kernel - [PATCH 5.10 411/717] samples/bpf: Fix possible hang in xdpsock with multiple threads

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Date:   Mon, 28 Dec 2020 13:46:49 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Magnus Karlsson <magnus.karlsson@...el.com>,
        Daniel Borkmann <daniel@...earbox.net>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.10 411/717] samples/bpf: Fix possible hang in xdpsock with multiple threads

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

[ Upstream commit 092fde0f863b72b67c4d6dc03844f5658fc00a35 ]

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, return from the function.

Fixes: cd9e72b6f210 ("samples/bpf: xdpsock: Add option to specify batch size")
Signed-off-by: Magnus Karlsson <magnus.karlsson@...el.com>
Signed-off-by: Daniel Borkmann <daniel@...earbox.net>
Link: https://lore.kernel.org/bpf/20201210163407.22066-1-magnus.karlsson@gmail.com
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 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 1149e94ca32fd..33c58de58626c 100644
--- a/samples/bpf/xdpsock_user.c
+++ b/samples/bpf/xdpsock_user.c
@@ -1250,6 +1250,8 @@ 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)
+			return;
 	}
 
 	for (i = 0; i < batch_size; i++) {
-- 
2.27.0