Re: [PATCH v10 0/6] selftests/mm: refactor pkey helpers and fix mmap error handling

[Andrew Morton <akpm@linux-foundation.org>]

On Mon,  6 Jul 2026 16:15:54 +0800 Hongfu Li <lihongfu@kylinos.cn> wrote:

> The main changes in this series are to refactor shared tracing and assertion
> helpers into a common file, unify both pkey selftests on pkey_assert() and
> per-test tracing for consistent diagnostics, and add missing mmap() return
> checks with MAP_FAILED used throughout for readability and consistency.

Thanks, I've updated mm.git to this version.

> v10:
> - Add patch 6/6 to fix a pre-existing cleartid race: remove unused
>   settid/cleartid clone flags and wait for the clone child to exit in
>   the sigsegv test.

Below is how v10 altered mm.git.  As you mentioned, this is all from
the addition of [patch 6/6].

btw, I thought the official way to wait for a child thread to exit is
pthread_join()?  Why is that sched_yield() loop used?


 tools/testing/selftests/mm/pkey_sighandler_tests.c |   20 ++++++-----
 1 file changed, 12 insertions(+), 8 deletions(-)

--- a/tools/testing/selftests/mm/pkey_sighandler_tests.c~b
+++ a/tools/testing/selftests/mm/pkey_sighandler_tests.c
@@ -290,7 +290,6 @@ static void test_sigsegv_handler_with_di
 	static stack_t sigstack;
 	void *stack;
 	int pkey;
-	int parent_pid = 0;
 	int child_pid = 0;
 	u64 pkey_reg;
 	long ret;
@@ -330,11 +329,10 @@ static void test_sigsegv_handler_with_di
 	/* Use clone to avoid newer glibcs using rseq on new threads */
 	ret = clone_raw(CLONE_VM | CLONE_FS | CLONE_FILES |
 			CLONE_SIGHAND | CLONE_THREAD | CLONE_SYSVSEM |
-			CLONE_PARENT_SETTID | CLONE_CHILD_CLEARTID |
 			CLONE_DETACHED,
 			stack + STACK_SIZE,
-			&parent_pid,
-			&child_pid);
+			NULL,
+			NULL);
 
 	if (ret < 0) {
 		errno = -ret;
@@ -344,11 +342,19 @@ static void test_sigsegv_handler_with_di
 		syscall_raw(SYS_exit, 0, 0, 0, 0, 0, 0);
 	}
 
+	child_pid = ret;
+
 	pthread_mutex_lock(&mutex);
 	while (siginfo.si_signo == 0)
 		pthread_cond_wait(&cond, &mutex);
 	pthread_mutex_unlock(&mutex);
 
+	/* Wait for child to exit before returning */
+	do {
+		sched_yield();
+		ret = syscall_raw(SYS_tkill, child_pid, 0, 0, 0, 0, 0);
+	} while (ret != -ESRCH && ret != -EINVAL);
+
 	ksft_test_result(siginfo.si_signo == SIGSEGV &&
 			 siginfo.si_code == SEGV_MAPERR &&
 			 siginfo.si_addr == NULL,
@@ -445,7 +451,6 @@ static void test_pkru_sigreturn(void)
 	static stack_t sigstack;
 	void *stack;
 	int pkey;
-	int parent_pid = 0;
 	int child_pid = 0;
 	u64 pkey_reg;
 	long ret;
@@ -504,11 +509,10 @@ static void test_pkru_sigreturn(void)
 	/* Use clone to avoid newer glibcs using rseq on new threads */
 	ret = clone_raw(CLONE_VM | CLONE_FS | CLONE_FILES |
 			CLONE_SIGHAND | CLONE_THREAD | CLONE_SYSVSEM |
-			CLONE_PARENT_SETTID | CLONE_CHILD_CLEARTID |
 			CLONE_DETACHED,
 			stack + STACK_SIZE,
-			&parent_pid,
-			&child_pid);
+			NULL,
+			NULL);
 
 	if (ret < 0) {
 		errno = -ret;
_