From 9a5f25ad30e5bb40a2e0c61c991594d3e6529c0a Mon Sep 17 00:00:00 2001 From: Andrii Nakryiko Date: Mon, 1 Jun 2020 22:03:49 -0700 Subject: [PATCH] selftests/bpf: Fix sample_cnt shared between two threads Make sample_cnt volatile to fix possible selftests failure due to compiler optimization preventing latest sample_cnt value to be visible to main thread. sample_cnt is incremented in background thread, which is then joined into main thread. So in terms of visibility sample_cnt update is ok. But because it's not volatile, compiler might make optimizations that would prevent main thread to see latest updated value. Fix this by marking global variable volatile. Fixes: cb1c9ddd5525 ("selftests/bpf: Add BPF ringbuf selftests") Signed-off-by: Andrii Nakryiko Signed-off-by: Alexei Starovoitov Acked-by: Song Liu Link: https://lore.kernel.org/bpf/20200602050349.215037-1-andriin@fb.com --- tools/testing/selftests/bpf/prog_tests/ringbuf.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/tools/testing/selftests/bpf/prog_tests/ringbuf.c b/tools/testing/selftests/bpf/prog_tests/ringbuf.c index bb8541f240e2..2bba908dfa63 100644 --- a/tools/testing/selftests/bpf/prog_tests/ringbuf.c +++ b/tools/testing/selftests/bpf/prog_tests/ringbuf.c @@ -25,7 +25,7 @@ struct sample { char comm[16]; }; -static int sample_cnt; +static volatile int sample_cnt; static int process_sample(void *ctx, void *data, size_t len) { -- 2.11.0