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SubjectRe: [PATCH] selftests/seccomp: Actually sleep for 1/10th second
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On 1/27/19 11:36 AM, Nick Desaulniers wrote:
> On Sun, Jan 27, 2019 at 11:13 AM Kees Cook <keescook@chromium.org> wrote:
>>
>> On Sun, Jan 27, 2019 at 11:25 PM Nick Desaulniers
>> <ndesaulniers@google.com> wrote:
>>>
>>> On Sun, Jan 27, 2019 at 1:44 AM Kees Cook <keescook@chromium.org> wrote:
>>>>
>>>> Clang noticed that some none-zero sleep()s were actually using zero
>>>> anyway. This switches to nanosleep() to gain sub-second granularity.
>>>>
>>>> seccomp_bpf.c:2625:9: warning: implicit conversion from 'double' to
>>>> 'unsigned int' changes value from 0.1 to 0 [-Wliteral-conversion]
>>>> sleep(0.1);
>>>> ~~~~~ ^~~
>>>>
>>>> Signed-off-by: Kees Cook <keescook@chromium.org>
>>>> ---
>>>> tools/testing/selftests/seccomp/seccomp_bpf.c | 5 +++--
>>>> 1 file changed, 3 insertions(+), 2 deletions(-)
>>>>
>>>> diff --git a/tools/testing/selftests/seccomp/seccomp_bpf.c b/tools/testing/selftests/seccomp/seccomp_bpf.c
>>>> index 067cb4607d6c..a9f278c13f13 100644
>>>> --- a/tools/testing/selftests/seccomp/seccomp_bpf.c
>>>> +++ b/tools/testing/selftests/seccomp/seccomp_bpf.c
>>>> @@ -2569,6 +2569,7 @@ TEST_F(TSYNC, two_siblings_not_under_filter)
>>>> {
>>>> long ret, sib;
>>>> void *status;
>>>> + struct timespec delay = { .tv_nsec = 100000000 };
>>>
>>> "Omitted fields are implicitly initialized the same as for objects
>>> that have static storage duration."
>>> https://gcc.gnu.org/onlinedocs/gcc/Designated-Inits.html
>>> https://godbolt.org/z/cuGqxM
>>> (So this wont sleep an arbitrary amount of seconds, phew)
>>
>> Yup. :) Even an empty initializer works ... = { };
>> (Except that padding bytes aren't always included in the zeroing...)
>>
>>>
>>>>
>>>> ASSERT_EQ(0, prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0)) {
>>>> TH_LOG("Kernel does not support PR_SET_NO_NEW_PRIVS!");
>>>> @@ -2622,7 +2623,7 @@ TEST_F(TSYNC, two_siblings_not_under_filter)
>>>> EXPECT_EQ(SIBLING_EXIT_UNKILLED, (long)status);
>>>> /* Poll for actual task death. pthread_join doesn't guarantee it. */
>>>> while (!kill(self->sibling[sib].system_tid, 0))
>>>> - sleep(0.1);
>>>> + nanosleep(&delay, NULL);
>>>> /* Switch to the remaining sibling */
>>>> sib = !sib;
>>>>
>>>> @@ -2647,7 +2648,7 @@ TEST_F(TSYNC, two_siblings_not_under_filter)
>>>> EXPECT_EQ(0, (long)status);
>>>> /* Poll for actual task death. pthread_join doesn't guarantee it. */
>>>> while (!kill(self->sibling[sib].system_tid, 0))
>>>> - sleep(0.1);
>>>> + nanosleep(&delay, NULL);
>>>
>>> Interesting bug. If the sleeps weren't doing anything, are they even
>>> needed? Does adding the tests cause them to continue to pass, or start
>>> to fail? If they weren't doing anything, and the tests were passing,
>>> maybe it's just better to remove them?
>>
>> It was just spinning.
>
> So this test has been broken? If so, do you know for how long? Or
> who's monitoring them? Either way, thanks for noticing and fixing.
>
> +Guenter; did you notice if this test was failing? Are your boot tests
> running kselftests?
>

No, I don't run kselftests at this time.

Guenter

>> This restores the intention of not being so
>> aggressive in the wait loop. While the sleep could be removed, that
>> wasn't the intention.
>
> Oh, yeah I guess the comment above it about pthread_join is relevant.
> I just get highly highly suspicious whenever I see sleeps added to any
> code.
> Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
>

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