Reviewed-by: Benoît Canet <ben...@scylladb.com>
2017-01-18 10:32 GMT+01:00 Nadav Har'El <n...@scylladb.com>:
> Allow unpinning a thread with pthread_setaffinity_np() and
> sched_setaffinity() by setting the CPU mask to all CPUs.
>
> We still do not support setting the CPU mask to an arbitrary subset of
> CPUs - just to either one CPU, or all of them.
>
> Fixes #778
>
> Signed-off-by: Nadav Har'El <n...@scylladb.com>
> ---
> libc/pthread.cc | 2 ++
> tests/tst-pthread-affinity.cc | 47 ++++++++++++++++++++++++++++++
> +++++++++++++
> 2 files changed, 49 insertions(+)
>
> diff --git a/libc/pthread.cc b/libc/pthread.cc
> index 62de17d..1322a26 100644
> --- a/libc/pthread.cc
> +++ b/libc/pthread.cc
> @@ -1013,6 +1013,8 @@ static int setaffinity(sched::thread* t, size_t
> cpusetsize,
> }
> }
> }
> + } else if (count == (int)sched::cpus.size()) {
> + t->unpin();
> } else {
> WARN_ONCE("Warning: OSv only supports cpu_set_t with at most one "
> "CPU set.\n pthread_setaffinity_np or sched_setaffinity
> ignored.\n");
> diff --git a/tests/tst-pthread-affinity.cc b/tests/tst-pthread-affinity.cc
> index 142b6a7..b62924f 100644
> --- a/tests/tst-pthread-affinity.cc
> +++ b/tests/tst-pthread-affinity.cc
> @@ -35,6 +35,49 @@ void *get_processor(void *cpuid)
> return NULL;
> }
>
> +// Test that we can pin an existing thread to a specific CPU and then to
> unpin
> +// it by changing its affinity to all CPUs. Currently we test this only
> on the
> +// current thread.
> +void *test_pin_unpin(void *)
> +{
> + unsigned ncpus = sched::cpus.size();
> + // The thread starts with affinity to all cpus
> + cpu_set_t cs;
> + CPU_ZERO(&cs);
> + report("getaffinity", pthread_getaffinity_np(pthread_self(),
> sizeof(cs), &cs) == 0);
> + bool success = true;
> + for (unsigned i = 0; i < ncpus; i++) {
> + success = success && CPU_ISSET(i, &cs);
> + }
> + report("thread is initially unpinned", success);
> + // Pin the thread to cpu 0 only, and check it worked
> + CPU_ZERO(&cs);
> + CPU_SET(0, &cs);
> + report("setaffinity", pthread_setaffinity_np(pthread_self(),
> sizeof(cs), &cs) == 0);
> + CPU_ZERO(&cs);
> + report("getaffinity", pthread_getaffinity_np(pthread_self(),
> sizeof(cs), &cs) == 0);
> + success = CPU_ISSET(0, &cs);
> + for (unsigned i = 1; i < ncpus; i++) {
> + success = success && !CPU_ISSET(i, &cs);
> + }
> + report("thread is now pinned to cpu 0", success);
> + // Unpin the thread (set its affinity to all CPUs) and confirm it
> worked
> + CPU_ZERO(&cs);
> + for (unsigned i = 0; i < ncpus; i++) {
> + CPU_SET(i, &cs);
> + }
> + report("setaffinity", pthread_setaffinity_np(pthread_self(),
> sizeof(cs), &cs) == 0);
> + CPU_ZERO(&cs);
> + report("getaffinity", pthread_getaffinity_np(pthread_self(),
> sizeof(cs), &cs) == 0);
> + success = true;
> + for (unsigned i = 0; i < ncpus; i++) {
> + success = success && CPU_ISSET(i, &cs);
> + }
> + report("thread is now unpinned again", success);
> +
> + return nullptr;
> +}
> +
> int main(void)
> {
> printf("starting pthread affinity test\n");
> @@ -111,6 +154,10 @@ int main(void)
> }
> report("All bits were set", success);
>
> + // Test that we can pin and unpin an existing thread
> + pthread_create(&thread, nullptr, test_pin_unpin, nullptr);
> + pthread_join(thread, nullptr);
> +
> printf("SUMMARY: %u tests / %u failures\n", tests_total.load(),
> tests_failed.load());
> return tests_failed == 0 ? 0 : 1;
> }
> --
> 2.9.3
>
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