[PATCH 3/5] selftests/powerpc/dscr: Improve DSCR explicit random test case
Benjamin Gray
bgray at linux.ibm.com
Tue Mar 7 11:55:13 AEDT 2023
The tests currently have a single writer thread updating the system
DSCR with a 1/1000 chance looped only 100 times. So only around one in
10 runs actually do anything.
* Add multiple threads to the dscr_explicit_random_test case.
* Use a barrier to make all the threads start work as simultaneously as
possible.
* Use a rwlock and make all threads have a reasonable chance to write to
the DSCR on each iteration.
PTHREAD_RWLOCK_PREFER_WRITER_NONRECURSIVE_NP is used to prevent
writers from starving while all the other threads keep reading.
Logging the reads/writes shows a decent mix across the whole test.
* Allow all threads a chance to write.
* Make the chance of writing more likely.
Signed-off-by: Benjamin Gray <bgray at linux.ibm.com>
---
tools/testing/selftests/powerpc/dscr/dscr.h | 5 -
.../powerpc/dscr/dscr_default_test.c | 132 ++++++++----------
.../powerpc/dscr/dscr_explicit_test.c | 94 ++++++++-----
3 files changed, 114 insertions(+), 117 deletions(-)
diff --git a/tools/testing/selftests/powerpc/dscr/dscr.h b/tools/testing/selftests/powerpc/dscr/dscr.h
index 903ee0c83fac..9cd5488ab7c2 100644
--- a/tools/testing/selftests/powerpc/dscr/dscr.h
+++ b/tools/testing/selftests/powerpc/dscr/dscr.h
@@ -88,11 +88,6 @@ void set_default_dscr(unsigned long val)
}
}
-double uniform_deviate(int seed)
-{
- return seed * (1.0 / (RAND_MAX + 1.0));
-}
-
int restrict_to_one_cpu(void)
{
cpu_set_t cpus;
diff --git a/tools/testing/selftests/powerpc/dscr/dscr_default_test.c b/tools/testing/selftests/powerpc/dscr/dscr_default_test.c
index 8b7d0ff8a20a..758823d59daa 100644
--- a/tools/testing/selftests/powerpc/dscr/dscr_default_test.c
+++ b/tools/testing/selftests/powerpc/dscr/dscr_default_test.c
@@ -69,105 +69,85 @@ int dscr_default_lockstep_test(void)
return 0;
}
-static unsigned long dscr; /* System DSCR default */
-static unsigned long sequence;
-static unsigned long result[THREADS];
+struct random_thread_args {
+ pthread_t thread_id;
+ unsigned long *expected_system_dscr;
+ pthread_rwlock_t *rw_lock;
+ pthread_barrier_t *barrier;
+};
-static void *do_test(void *in)
+static void *dscr_default_random_thread(void *in)
{
- unsigned long thread = (unsigned long)in;
- unsigned long i;
+ struct random_thread_args *args = (struct random_thread_args *)in;
+ unsigned long *expected_dscr_p = args->expected_system_dscr;
+ pthread_rwlock_t *rw_lock = args->rw_lock;
+ int err;
- for (i = 0; i < COUNT; i++) {
- unsigned long d, cur_dscr, cur_dscr_usr;
- unsigned long s1, s2;
+ srand(gettid());
- s1 = READ_ONCE(sequence);
- if (s1 & 1)
- continue;
- rmb();
+ err = pthread_barrier_wait(args->barrier);
+ FAIL_IF_EXIT(err != 0 && err != PTHREAD_BARRIER_SERIAL_THREAD);
- d = dscr;
- cur_dscr = get_dscr();
- cur_dscr_usr = get_dscr_usr();
+ for (int i = 0; i < COUNT; i++) {
+ unsigned long expected_dscr;
+ unsigned long current_dscr;
+ unsigned long current_dscr_usr;
- rmb();
- s2 = sequence;
+ FAIL_IF_EXIT(pthread_rwlock_rdlock(rw_lock));
+ expected_dscr = *expected_dscr_p;
+ current_dscr = get_dscr();
+ current_dscr_usr = get_dscr_usr();
+ FAIL_IF_EXIT(pthread_rwlock_unlock(rw_lock));
- if (s1 != s2)
- continue;
+ FAIL_IF_EXIT(current_dscr != expected_dscr);
+ FAIL_IF_EXIT(current_dscr_usr != expected_dscr);
- if (cur_dscr != d) {
- fprintf(stderr, "thread %ld kernel DSCR should be %ld "
- "but is %ld\n", thread, d, cur_dscr);
- result[thread] = 1;
- pthread_exit(&result[thread]);
- }
+ if (rand() % 10 == 0) {
+ unsigned long next_dscr;
- if (cur_dscr_usr != d) {
- fprintf(stderr, "thread %ld user DSCR should be %ld "
- "but is %ld\n", thread, d, cur_dscr_usr);
- result[thread] = 1;
- pthread_exit(&result[thread]);
+ FAIL_IF_EXIT(pthread_rwlock_wrlock(rw_lock));
+ next_dscr = (*expected_dscr_p + 1) % DSCR_MAX;
+ set_default_dscr(next_dscr);
+ *expected_dscr_p = next_dscr;
+ FAIL_IF_EXIT(pthread_rwlock_unlock(rw_lock));
}
}
- result[thread] = 0;
- pthread_exit(&result[thread]);
+
+ pthread_exit((void *)0);
}
int dscr_default_random_test(void)
{
- pthread_t threads[THREADS];
- unsigned long i, *status[THREADS];
+ struct random_thread_args threads[THREADS];
+ unsigned long expected_system_dscr = 0;
+ pthread_rwlockattr_t rwlock_attr;
+ pthread_rwlock_t rw_lock;
+ pthread_barrier_t barrier;
SKIP_IF(!have_hwcap2(PPC_FEATURE2_DSCR));
- /* Initial DSCR default */
- dscr = 1;
- set_default_dscr(dscr);
+ FAIL_IF(pthread_rwlockattr_setkind_np(&rwlock_attr,
+ PTHREAD_RWLOCK_PREFER_WRITER_NONRECURSIVE_NP));
+ FAIL_IF(pthread_rwlock_init(&rw_lock, &rwlock_attr));
+ FAIL_IF(pthread_barrier_init(&barrier, NULL, THREADS));
- /* Spawn all testing threads */
- for (i = 0; i < THREADS; i++) {
- if (pthread_create(&threads[i], NULL, do_test, (void *)i)) {
- perror("pthread_create() failed");
- return 1;
- }
+ set_default_dscr(expected_system_dscr);
+
+ for (int i = 0; i < THREADS; i++) {
+ threads[i].expected_system_dscr = &expected_system_dscr;
+ threads[i].rw_lock = &rw_lock;
+ threads[i].barrier = &barrier;
+
+ FAIL_IF(pthread_create(&threads[i].thread_id, NULL,
+ dscr_default_random_thread, (void *)&threads[i]));
}
- srand(getpid());
+ for (int i = 0; i < THREADS; i++)
+ FAIL_IF(pthread_join(threads[i].thread_id, NULL));
- /* Keep changing the DSCR default */
- for (i = 0; i < COUNT; i++) {
- double ret = uniform_deviate(rand());
+ FAIL_IF(pthread_barrier_destroy(&barrier));
+ FAIL_IF(pthread_rwlock_destroy(&rw_lock));
- if (ret < 0.0001) {
- sequence++;
- wmb();
-
- dscr++;
- if (dscr > DSCR_MAX)
- dscr = 0;
-
- set_default_dscr(dscr);
-
- wmb();
- sequence++;
- }
- }
-
- /* Individual testing thread exit status */
- for (i = 0; i < THREADS; i++) {
- if (pthread_join(threads[i], (void **)&(status[i]))) {
- perror("pthread_join() failed");
- return 1;
- }
-
- if (*status[i]) {
- printf("%ldth thread failed to join with %ld status\n",
- i, *status[i]);
- return 1;
- }
- }
return 0;
}
diff --git a/tools/testing/selftests/powerpc/dscr/dscr_explicit_test.c b/tools/testing/selftests/powerpc/dscr/dscr_explicit_test.c
index 28b1ea23e469..9930533730ae 100644
--- a/tools/testing/selftests/powerpc/dscr/dscr_explicit_test.c
+++ b/tools/testing/selftests/powerpc/dscr/dscr_explicit_test.c
@@ -86,50 +86,72 @@ int dscr_explicit_lockstep_test(void)
return 0;
}
+struct random_thread_args {
+ pthread_t thread_id;
+ bool do_yields;
+ pthread_barrier_t *barrier;
+};
+
+void *dscr_explicit_random_thread(void *in)
+{
+ struct random_thread_args *args = (struct random_thread_args *)in;
+ unsigned long expected_dscr = 0;
+ int err;
+
+ srand(gettid());
+
+ err = pthread_barrier_wait(args->barrier);
+ FAIL_IF_EXIT(err != 0 && err != PTHREAD_BARRIER_SERIAL_THREAD);
+
+ for (int i = 0; i < COUNT; i++) {
+ expected_dscr = rand() % DSCR_MAX;
+ set_dscr(expected_dscr);
+
+ for (int j = rand() % 5; j > 0; --j) {
+ FAIL_IF_EXIT(get_dscr() != expected_dscr);
+ FAIL_IF_EXIT(get_dscr_usr() != expected_dscr);
+
+ if (args->do_yields && rand() % 2)
+ sched_yield();
+ }
+
+ expected_dscr = rand() % DSCR_MAX;
+ set_dscr_usr(expected_dscr);
+
+ for (int j = rand() % 5; j > 0; --j) {
+ FAIL_IF_EXIT(get_dscr() != expected_dscr);
+ FAIL_IF_EXIT(get_dscr_usr() != expected_dscr);
+
+ if (args->do_yields && rand() % 2)
+ sched_yield();
+ }
+ }
+
+ return NULL;
+}
+
int dscr_explicit_random_test(void)
{
- unsigned long i, dscr = 0;
+ struct random_thread_args threads[THREADS];
+ pthread_barrier_t barrier;
SKIP_IF(!have_hwcap2(PPC_FEATURE2_DSCR));
- srand(getpid());
- set_dscr(dscr);
+ FAIL_IF(pthread_barrier_init(&barrier, NULL, THREADS));
- for (i = 0; i < COUNT; i++) {
- unsigned long cur_dscr, cur_dscr_usr;
- double ret = uniform_deviate(rand());
+ for (int i = 0; i < THREADS; i++) {
+ threads[i].do_yields = i % 2 == 0;
+ threads[i].barrier = &barrier;
- if (ret < 0.001) {
- dscr++;
- if (dscr > DSCR_MAX)
- dscr = 0;
-
- set_dscr(dscr);
- }
-
- cur_dscr = get_dscr();
- if (cur_dscr != dscr) {
- fprintf(stderr, "Kernel DSCR should be %ld but "
- "is %ld\n", dscr, cur_dscr);
- return 1;
- }
-
- ret = uniform_deviate(rand());
- if (ret < 0.001) {
- dscr++;
- if (dscr > DSCR_MAX)
- dscr = 0;
-
- set_dscr_usr(dscr);
- }
-
- cur_dscr_usr = get_dscr_usr();
- if (cur_dscr_usr != dscr) {
- fprintf(stderr, "User DSCR should be %ld but "
- "is %ld\n", dscr, cur_dscr_usr);
- return 1;
- }
+ FAIL_IF(pthread_create(&threads[i].thread_id, NULL,
+ dscr_explicit_random_thread, (void *)&threads[i]));
}
+
+ for (int i = 0; i < THREADS; i++)
+ FAIL_IF(pthread_join(threads[i].thread_id, NULL));
+
+ FAIL_IF(pthread_barrier_destroy(&barrier));
+
return 0;
}
--
2.39.2
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