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Subject[PATCH v8 3/3] rseq/selftests: test MEMBARRIER_CMD_PRIVATE_EXPEDITED_RSEQ
From
Based on Google-internal RSEQ work done by
Paul Turner and Andrew Hunter.

This patch adds a selftest for MEMBARRIER_CMD_PRIVATE_EXPEDITED_RSEQ.
The test quite often fails without the previous patch in this patchset,
but consistently passes with it.

v3: added rseq_offset_deref_addv() to x86_64 to make the test
more explicit; on other architectures I kept using existing
rseq_cmpeqv_cmpeqv_storev() as I have no easy way to test
there. Added a comment explaining why the test works this way.
v4: skipped the test if rseq_offset_deref_addv() is not present
(that is, on all architectures other than x86_64).
v8: split rseq_offset_deref_addv() into a separate patch;
moved the test to param_test; other minor tweaks.

Signed-off-by: Peter Oskolkov <posk@google.com>
---
tools/testing/selftests/rseq/param_test.c | 223 +++++++++++++++++-
.../testing/selftests/rseq/run_param_test.sh | 2 +
2 files changed, 224 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/rseq/param_test.c b/tools/testing/selftests/rseq/param_test.c
index e8a657a5f48a..384589095864 100644
--- a/tools/testing/selftests/rseq/param_test.c
+++ b/tools/testing/selftests/rseq/param_test.c
@@ -1,8 +1,10 @@
// SPDX-License-Identifier: LGPL-2.1
#define _GNU_SOURCE
#include <assert.h>
+#include <linux/membarrier.h>
#include <pthread.h>
#include <sched.h>
+#include <stdatomic.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
@@ -1131,6 +1133,220 @@ static int set_signal_handler(void)
return ret;
}

+struct test_membarrier_thread_args {
+ int stop;
+ intptr_t percpu_list_ptr;
+};
+
+/* Worker threads modify data in their "active" percpu lists. */
+void *test_membarrier_worker_thread(void *arg)
+{
+ struct test_membarrier_thread_args *args =
+ (struct test_membarrier_thread_args *)arg;
+ const int iters = opt_reps;
+ int i;
+
+ if (rseq_register_current_thread()) {
+ fprintf(stderr, "Error: rseq_register_current_thread(...) failed(%d): %s\n",
+ errno, strerror(errno));
+ abort();
+ }
+
+ /* Wait for initialization. */
+ while (!atomic_load(&args->percpu_list_ptr)) {}
+
+ for (i = 0; i < iters; ++i) {
+ int ret;
+
+ do {
+ int cpu = rseq_cpu_start();
+
+ ret = rseq_offset_deref_addv(&args->percpu_list_ptr,
+ sizeof(struct percpu_list_entry) * cpu, 1, cpu);
+ } while (rseq_unlikely(ret));
+ }
+
+ if (rseq_unregister_current_thread()) {
+ fprintf(stderr, "Error: rseq_unregister_current_thread(...) failed(%d): %s\n",
+ errno, strerror(errno));
+ abort();
+ }
+ return NULL;
+}
+
+void test_membarrier_init_percpu_list(struct percpu_list *list)
+{
+ int i;
+
+ memset(list, 0, sizeof(*list));
+ for (i = 0; i < CPU_SETSIZE; i++) {
+ struct percpu_list_node *node;
+
+ node = malloc(sizeof(*node));
+ assert(node);
+ node->data = 0;
+ node->next = NULL;
+ list->c[i].head = node;
+ }
+}
+
+void test_membarrier_free_percpu_list(struct percpu_list *list)
+{
+ int i;
+
+ for (i = 0; i < CPU_SETSIZE; i++)
+ free(list->c[i].head);
+}
+
+static int sys_membarrier(int cmd, int flags, int cpu_id)
+{
+ return syscall(__NR_membarrier, cmd, flags, cpu_id);
+}
+
+/*
+ * The manager thread swaps per-cpu lists that worker threads see,
+ * and validates that there are no unexpected modifications.
+ */
+void *test_membarrier_manager_thread(void *arg)
+{
+ struct test_membarrier_thread_args *args =
+ (struct test_membarrier_thread_args *)arg;
+ struct percpu_list list_a, list_b;
+ intptr_t expect_a = 0, expect_b = 0;
+ int cpu_a = 0, cpu_b = 0;
+
+ if (rseq_register_current_thread()) {
+ fprintf(stderr, "Error: rseq_register_current_thread(...) failed(%d): %s\n",
+ errno, strerror(errno));
+ abort();
+ }
+
+ /* Init lists. */
+ test_membarrier_init_percpu_list(&list_a);
+ test_membarrier_init_percpu_list(&list_b);
+
+ atomic_store(&args->percpu_list_ptr, (intptr_t)&list_a);
+
+ while (!atomic_load(&args->stop)) {
+ /* list_a is "active". */
+ cpu_a = rand() % CPU_SETSIZE;
+ /*
+ * As list_b is "inactive", we should never see changes
+ * to list_b.
+ */
+ if (expect_b != atomic_load(&list_b.c[cpu_b].head->data)) {
+ fprintf(stderr, "Membarrier test failed\n");
+ abort();
+ }
+
+ /* Make list_b "active". */
+ atomic_store(&args->percpu_list_ptr, (intptr_t)&list_b);
+ if (sys_membarrier(MEMBARRIER_CMD_PRIVATE_EXPEDITED_RSEQ,
+ MEMBARRIER_CMD_FLAG_CPU, cpu_a) &&
+ errno != ENXIO /* missing CPU */) {
+ perror("sys_membarrier");
+ abort();
+ }
+ /*
+ * Cpu A should now only modify list_b, so the values
+ * in list_a should be stable.
+ */
+ expect_a = atomic_load(&list_a.c[cpu_a].head->data);
+
+ cpu_b = rand() % CPU_SETSIZE;
+ /*
+ * As list_a is "inactive", we should never see changes
+ * to list_a.
+ */
+ if (expect_a != atomic_load(&list_a.c[cpu_a].head->data)) {
+ fprintf(stderr, "Membarrier test failed\n");
+ abort();
+ }
+
+ /* Make list_a "active". */
+ atomic_store(&args->percpu_list_ptr, (intptr_t)&list_a);
+ if (sys_membarrier(MEMBARRIER_CMD_PRIVATE_EXPEDITED_RSEQ,
+ MEMBARRIER_CMD_FLAG_CPU, cpu_b) &&
+ errno != ENXIO /* missing CPU*/) {
+ perror("sys_membarrier");
+ abort();
+ }
+ /* Remember a value from list_b. */
+ expect_b = atomic_load(&list_b.c[cpu_b].head->data);
+ }
+
+ test_membarrier_free_percpu_list(&list_a);
+ test_membarrier_free_percpu_list(&list_b);
+
+ if (rseq_unregister_current_thread()) {
+ fprintf(stderr, "Error: rseq_unregister_current_thread(...) failed(%d): %s\n",
+ errno, strerror(errno));
+ abort();
+ }
+ return NULL;
+}
+
+/* Test MEMBARRIER_CMD_PRIVATE_RESTART_RSEQ_ON_CPU membarrier command. */
+#ifdef RSEQ_ARCH_HAS_OFFSET_DEREF_ADDV
+void test_membarrier(void)
+{
+ const int num_threads = opt_threads;
+ struct test_membarrier_thread_args thread_args;
+ pthread_t worker_threads[num_threads];
+ pthread_t manager_thread;
+ int i, ret;
+
+ if (sys_membarrier(MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED_RSEQ, 0, 0)) {
+ perror("sys_membarrier");
+ abort();
+ }
+
+ thread_args.stop = 0;
+ thread_args.percpu_list_ptr = 0;
+ ret = pthread_create(&manager_thread, NULL,
+ test_membarrier_manager_thread, &thread_args);
+ if (ret) {
+ errno = ret;
+ perror("pthread_create");
+ abort();
+ }
+
+ for (i = 0; i < num_threads; i++) {
+ ret = pthread_create(&worker_threads[i], NULL,
+ test_membarrier_worker_thread, &thread_args);
+ if (ret) {
+ errno = ret;
+ perror("pthread_create");
+ abort();
+ }
+ }
+
+
+ for (i = 0; i < num_threads; i++) {
+ ret = pthread_join(worker_threads[i], NULL);
+ if (ret) {
+ errno = ret;
+ perror("pthread_join");
+ abort();
+ }
+ }
+
+ atomic_store(&thread_args.stop, 1);
+ ret = pthread_join(manager_thread, NULL);
+ if (ret) {
+ errno = ret;
+ perror("pthread_join");
+ abort();
+ }
+}
+#else /* RSEQ_ARCH_HAS_OFFSET_DEREF_ADDV */
+void test_membarrier(void)
+{
+ fprintf(stderr, "rseq_offset_deref_addv is not implemented on this architecture. "
+ "Skipping membarrier test.\n");
+}
+#endif
+
static void show_usage(int argc, char **argv)
{
printf("Usage : %s <OPTIONS>\n",
@@ -1153,7 +1369,7 @@ static void show_usage(int argc, char **argv)
printf(" [-r N] Number of repetitions per thread (default 5000)\n");
printf(" [-d] Disable rseq system call (no initialization)\n");
printf(" [-D M] Disable rseq for each M threads\n");
- printf(" [-T test] Choose test: (s)pinlock, (l)ist, (b)uffer, (m)emcpy, (i)ncrement\n");
+ printf(" [-T test] Choose test: (s)pinlock, (l)ist, (b)uffer, (m)emcpy, (i)ncrement, membarrie(r)\n");
printf(" [-M] Push into buffer and memcpy buffer with memory barriers.\n");
printf(" [-v] Verbose output.\n");
printf(" [-h] Show this help.\n");
@@ -1268,6 +1484,7 @@ int main(int argc, char **argv)
case 'i':
case 'b':
case 'm':
+ case 'r':
break;
default:
show_usage(argc, argv);
@@ -1320,6 +1537,10 @@ int main(int argc, char **argv)
printf_verbose("counter increment\n");
test_percpu_inc();
break;
+ case 'r':
+ printf_verbose("membarrier\n");
+ test_membarrier();
+ break;
}
if (!opt_disable_rseq && rseq_unregister_current_thread())
abort();
diff --git a/tools/testing/selftests/rseq/run_param_test.sh b/tools/testing/selftests/rseq/run_param_test.sh
index e426304fd4a0..f51bc83c9e41 100755
--- a/tools/testing/selftests/rseq/run_param_test.sh
+++ b/tools/testing/selftests/rseq/run_param_test.sh
@@ -15,6 +15,7 @@ TEST_LIST=(
"-T m"
"-T m -M"
"-T i"
+ "-T r"
)

TEST_NAME=(
@@ -25,6 +26,7 @@ TEST_NAME=(
"memcpy"
"memcpy with barrier"
"increment"
+ "membarrier"
)
IFS="$OLDIFS"

--
2.28.0.709.gb0816b6eb0-goog
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