Searched hist:d3b351f6 (Results 1 – 1 of 1) sorted by relevance
/openbmc/linux/tools/testing/selftests/bpf/prog_tests/ |
H A D | send_signal.c | d3b351f6 Thu Mar 10 18:37:21 CST 2022 Yonghong Song <yhs@fb.com> selftests/bpf: Fix a clang compilation error for send_signal.c
Building selftests/bpf with latest clang compiler (clang15 built from source), I hit the following compilation error:
/.../prog_tests/send_signal.c:43:16: error: variable 'j' set but not used [-Werror,-Wunused-but-set-variable] volatile int j = 0; ^ 1 error generated.
The problem also exists with clang13 and clang14. clang12 is okay.
In send_signal.c, we have the following code ...
volatile int j = 0; [...] for (int i = 0; i < 100000000 && !sigusr1_received; i++) j /= i + 1;
... to burn CPU cycles so bpf_send_signal() helper can be tested in NMI mode.
Slightly changing 'j /= i + 1' to 'j /= i + j + 1' or 'j++' can fix the problem. Further investigation indicated this should be a clang bug ([1]). The upstream fix will be proposed later. But it is a good idea to workaround the issue to unblock people who build kernel/selftests with clang.
[1] https://discourse.llvm.org/t/strange-clang-unused-but-set-variable-error-with-volatile-variables/60841
Signed-off-by: Yonghong Song <yhs@fb.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Link: https://lore.kernel.org/bpf/20220311003721.2177170-1-yhs@fb.com
|