From: Hou Tao <houtao1@xxxxxxxxxx>
When there are concurrent task local storage lookup operations,
if updates on per-cpu bpf_task_storage_busy is not preemption-safe,
some updates will be lost due to interleave, the final value of
bpf_task_storage_busy will not be zero and bpf_task_storage_trylock()
on specific cpu will fail forever.
So add a test case to ensure the update of per-cpu bpf_task_storage_busy
is preemption-safe.
Signed-off-by: Hou Tao <houtao1@xxxxxxxxxx>
---
.../bpf/prog_tests/task_local_storage.c | 91 +++++++++++++++++++
1 file changed, 91 insertions(+)
diff --git a/tools/testing/selftests/bpf/prog_tests/task_local_storage.c b/tools/testing/selftests/bpf/prog_tests/task_local_storage.c
index 035c263aab1b..ab8ee42a19e4 100644
--- a/tools/testing/selftests/bpf/prog_tests/task_local_storage.c
+++ b/tools/testing/selftests/bpf/prog_tests/task_local_storage.c
@@ -3,6 +3,7 @@
#define _GNU_SOURCE /* See feature_test_macros(7) */
#include <unistd.h>
+#include <sched.h>
#include <sys/syscall.h> /* For SYS_xxx definitions */
#include <sys/types.h>
#include <test_progs.h>
@@ -10,6 +11,14 @@
#include "task_local_storage_exit_creds.skel.h"
#include "task_ls_recursion.skel.h"
+struct lookup_ctx {
+ bool start;
+ bool stop;
+ int pid_fd;
+ int map_fd;
+ int loop;
+};
+
static void test_sys_enter_exit(void)
{
struct task_local_storage *skel;
@@ -81,6 +90,86 @@ static void test_recursion(void)
task_ls_recursion__destroy(skel);
}
+static void *lookup_fn(void *arg)
+{
+ struct lookup_ctx *ctx = arg;
+ long value;
+ int i = 0;
+
+ while (!ctx->start)
+ usleep(1);
+
+ while (!ctx->stop && i++ < ctx->loop)
+ bpf_map_lookup_elem(ctx->map_fd, &ctx->pid_fd, &value);
+ return NULL;
+}
+
+static void test_preemption(void)
+{
+ struct task_local_storage *skel;
+ struct lookup_ctx ctx;
+ unsigned int i, nr;
+ cpu_set_t old, new;
+ pthread_t *tids;
+ int err;
+
+ skel = task_local_storage__open_and_load();
+ if (!ASSERT_OK_PTR(skel, "skel_open_and_load"))
+ return;
+
+ /* Save the old affinity setting */
+ sched_getaffinity(getpid(), sizeof(old), &old);
+
+ /* Pinned on CPU 0 */
+ CPU_ZERO(&new);
+ CPU_SET(0, &new);
+ sched_setaffinity(getpid(), sizeof(new), &new);
+
+ nr = 256;
+ tids = calloc(nr, sizeof(*tids));
+ if (!ASSERT_NEQ(tids, NULL, "no mem"))
+ goto out;
+
+ ctx.start = false;
+ ctx.stop = false;
+ ctx.pid_fd = sys_pidfd_open(getpid(), 0);
+ ctx.map_fd = bpf_map__fd(skel->maps.enter_id);
+ ctx.loop = 8192;
+ for (i = 0; i < nr; i++) {
+ err = pthread_create(&tids[i], NULL, lookup_fn, &ctx);
+ if (err) {
+ unsigned int j;
+
+ ASSERT_OK(err, "pthread_create");
+
+ ctx.stop = true;
+ ctx.start = true;
+ for (j = 0; j < i; j++)
+ pthread_join(tids[j], NULL);
+ goto out;
+ }
+ }
+
+ ctx.start = true;
+ for (i = 0; i < nr; i++)
+ pthread_join(tids[i], NULL);
+
+ err = task_local_storage__attach(skel);
+ if (!ASSERT_OK(err, "skel_attach"))
+ goto out;
+
+ skel->bss->target_pid = syscall(SYS_gettid);
+ syscall(SYS_gettid);
+
+ /* If bpf_task_storage_trylock() fails, enter_cnt will be 0 */
+ ASSERT_EQ(skel->bss->enter_cnt, 1, "enter_cnt");
+out:
+ free(tids);
+ task_local_storage__destroy(skel);
+ /* Restore affinity setting */
+ sched_setaffinity(getpid(), sizeof(old), &old);
+}
+
void test_task_local_storage(void)
{
if (test__start_subtest("sys_enter_exit"))
@@ -89,4 +178,6 @@ void test_task_local_storage(void)
test_exit_creds();
if (test__start_subtest("recursion"))
test_recursion();
+ if (test__start_subtest("preemption"))
+ test_preemption();
}
--
2.29.2
