From: Andrii Nakryiko Date: Tue, 2 Jun 2020 05:03:49 +0000 (-0700) Subject: selftests/bpf: Fix sample_cnt shared between two threads X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=9a5f25ad30e5bb40a2e0c61c991594d3e6529c0a;p=linux.git 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 --- diff --git a/tools/testing/selftests/bpf/prog_tests/ringbuf.c b/tools/testing/selftests/bpf/prog_tests/ringbuf.c index bb8541f240e2a..2bba908dfa637 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) {