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Message-Id: <20200806000859.160882-2-posk@google.com>
Date: Wed, 5 Aug 2020 17:08:59 -0700
From: Peter Oskolkov <posk@...gle.com>
To: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
"Paul E . McKenney" <paulmck@...nel.org>,
linux-kernel@...r.kernel.org
Cc: Paul Turner <pjt@...gle.com>,
Chris Kennelly <ckennelly@...gle.com>,
Peter Oskolkov <posk@...k.io>, Peter Oskolkov <posk@...gle.com>
Subject: [PATCH 2/2] selftests/rseq: test MEMBARRIER_CMD_PRIVATE_RESTART_RSEQ_ON_CPU
Based on Google-internal RSEQ work done by
Paul Turner and Andrew Hunter.
This patch adds a selftest for MEMBARRIER_CMD_PRIVATE_RESTART_RSEQ_ON_CPU.
The test quite often fails without the previous patch in this patchset,
but consistently passes with it.
Signed-off-by: Peter Oskolkov <posk@...gle.com>
---
.../selftests/rseq/basic_percpu_ops_test.c | 181 ++++++++++++++++++
1 file changed, 181 insertions(+)
diff --git a/tools/testing/selftests/rseq/basic_percpu_ops_test.c b/tools/testing/selftests/rseq/basic_percpu_ops_test.c
index eb3f6db36d36..147c80deac19 100644
--- a/tools/testing/selftests/rseq/basic_percpu_ops_test.c
+++ b/tools/testing/selftests/rseq/basic_percpu_ops_test.c
@@ -3,16 +3,21 @@
#include <assert.h>
#include <pthread.h>
#include <sched.h>
+#include <stdatomic.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stddef.h>
+#include <syscall.h>
+#include <unistd.h>
#include "rseq.h"
#define ARRAY_SIZE(arr) (sizeof(arr) / sizeof((arr)[0]))
+#define MEMBARRIER_CMD_PRIVATE_RESTART_RSEQ_ON_CPU (1<<7)
+
struct percpu_lock_entry {
intptr_t v;
} __attribute__((aligned(128)));
@@ -289,6 +294,180 @@ void test_percpu_list(void)
assert(sum == expected_sum);
}
+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 = 10 * 1000 * 1000;
+ int i;
+
+ if (rseq_register_current_thread()) {
+ fprintf(stderr, "Error: rseq_register_current_thread(...) failed(%d): %s\n",
+ errno, strerror(errno));
+ abort();
+ }
+
+ for (i = 0; i < iters; ++i) {
+ while (true) {
+ int cpu, ret;
+ struct percpu_list *list_ptr = (struct percpu_list *)
+ atomic_load(&args->percpu_list_ptr);
+
+ if (!list_ptr)
+ continue; /* Not yet initialized. */
+
+ cpu = rseq_cpu_start();
+ struct percpu_list_node *node = list_ptr->c[cpu].head;
+ const intptr_t prev = node->data;
+
+ ret = rseq_cmpeqv_cmpeqv_storev(&node->data, prev,
+ &args->percpu_list_ptr,
+ (intptr_t)list_ptr, prev + 1, cpu);
+ if (!ret)
+ break; /* Success. */
+ }
+ }
+
+ 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)
+{
+ return syscall(__NR_membarrier, cmd, flags);
+}
+
+/*
+ * 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);
+ sys_membarrier(MEMBARRIER_CMD_PRIVATE_RESTART_RSEQ_ON_CPU, cpu_a);
+ /*
+ * Cpu A should now only modify list_b, so we 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);
+ sys_membarrier(MEMBARRIER_CMD_PRIVATE_RESTART_RSEQ_ON_CPU, cpu_b);
+ /* 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. */
+void test_membarrier(void)
+{
+ struct test_membarrier_thread_args thread_args;
+ pthread_t worker_threads[CPU_SETSIZE];
+ pthread_t manager_thread;
+ int i;
+
+ thread_args.stop = 0;
+ thread_args.percpu_list_ptr = 0;
+ pthread_create(&manager_thread, NULL,
+ test_membarrier_manager_thread, &thread_args);
+
+ for (i = 0; i < CPU_SETSIZE; i++)
+ pthread_create(&worker_threads[i], NULL,
+ test_membarrier_worker_thread, &thread_args);
+
+ for (i = 0; i < CPU_SETSIZE; i++)
+ pthread_join(worker_threads[i], NULL);
+
+ atomic_store(&thread_args.stop, 1);
+ pthread_join(manager_thread, NULL);
+}
+
int main(int argc, char **argv)
{
if (rseq_register_current_thread()) {
@@ -300,6 +479,8 @@ int main(int argc, char **argv)
test_percpu_spinlock();
printf("percpu_list\n");
test_percpu_list();
+ printf("membarrier\n");
+ test_membarrier();
if (rseq_unregister_current_thread()) {
fprintf(stderr, "Error: rseq_unregister_current_thread(...) failed(%d): %s\n",
errno, strerror(errno));
--
2.28.0.163.g6104cc2f0b6-goog
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