This is a note to let you know that I've just added the patch titled samples/bpf, xdpsock: Fix race when running for fix duration of time to the 5.15-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: samples-bpf-xdpsock-fix-race-when-running-for-fix-du.patch and it can be found in the queue-5.15 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. commit 888565d96c07df99fd5eca534e1d2031537ceeb6 Author: Niklas Söderlund <niklas.soderlund@xxxxxxxxxxxx> Date: Tue Mar 15 11:29:48 2022 +0100 samples/bpf, xdpsock: Fix race when running for fix duration of time [ Upstream commit 8fa42d78f6354bb96ad3a079dcbef528ca9fa9e0 ] When running xdpsock for a fix duration of time before terminating using --duration=<n>, there is a race condition that may cause xdpsock to terminate immediately. When running for a fixed duration of time the check to determine when to terminate execution is in is_benchmark_done() and is being executed in the context of the poller thread, if (opt_duration > 0) { unsigned long dt = (get_nsecs() - start_time); if (dt >= opt_duration) benchmark_done = true; } However start_time is only set after the poller thread have been created. This leaves a small window when the poller thread is starting and calls is_benchmark_done() for the first time that start_time is not yet set. In that case start_time have its initial value of 0 and the duration check fails as it do not correlate correctly for the applications start time and immediately sets benchmark_done which in turn terminates the xdpsock application. Fix this by setting start_time before creating the poller thread. Fixes: d3f11b018f6c ("samples/bpf: xdpsock: Add duration option to specify how long to run") Signed-off-by: Niklas Söderlund <niklas.soderlund@xxxxxxxxxxxx> Signed-off-by: Simon Horman <simon.horman@xxxxxxxxxxxx> Signed-off-by: Daniel Borkmann <daniel@xxxxxxxxxxxxx> Link: https://lore.kernel.org/bpf/20220315102948.466436-1-niklas.soderlund@xxxxxxxxxxxx Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> diff --git a/samples/bpf/xdpsock_user.c b/samples/bpf/xdpsock_user.c index 49d7a6ad7e39..1fb79b3ecdd5 100644 --- a/samples/bpf/xdpsock_user.c +++ b/samples/bpf/xdpsock_user.c @@ -1673,14 +1673,15 @@ int main(int argc, char **argv) setlocale(LC_ALL, ""); + prev_time = get_nsecs(); + start_time = prev_time; + if (!opt_quiet) { ret = pthread_create(&pt, NULL, poller, NULL); if (ret) exit_with_error(ret); } - prev_time = get_nsecs(); - start_time = prev_time; if (opt_bench == BENCH_RXDROP) rx_drop_all();