Merge tag 'mm-nonmm-stable-2026-02-18-19-56' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

Pull more non-MM updates from Andrew Morton:

 - "two fixes in kho_populate()" fixes a couple of not-major issues in
   the kexec handover code (Ran Xiaokai)

 - misc singletons

* tag 'mm-nonmm-stable-2026-02-18-19-56' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm:
  lib/group_cpus: handle const qualifier from clusters allocation type
  kho: remove unnecessary WARN_ON(err) in kho_populate()
  kho: fix missing early_memunmap() call in kho_populate()
  scripts/gdb: implement x86_page_ops in mm.py
  objpool: fix the overestimation of object pooling metadata size
  selftests/memfd: use IPC semaphore instead of SIGSTOP/SIGCONT
  delayacct: fix build regression on accounting tool

tools/testing/selftests/memfd/memfd_test.c

@@ -18,6 +18,9 @@
 #include <sys/stat.h>
 #include <sys/syscall.h>
 #include <sys/wait.h>
+#include <sys/types.h>
+#include <sys/ipc.h>
+#include <sys/sem.h>
 #include <unistd.h>
 #include <ctype.h>
 
@@ -39,6 +42,20 @@
 		    F_SEAL_EXEC)
 
 #define MFD_NOEXEC_SEAL	0x0008U
+union semun {
+	int val;
+	struct semid_ds *buf;
+	unsigned short int *array;
+	struct seminfo *__buf;
+};
+
+/*
+ * we use semaphores on nested wait tasks due the use of CLONE_NEWPID: the
+ * child will be PID 1 and can't send SIGSTOP to themselves due special
+ * treatment of the init task, so the SIGSTOP/SIGCONT synchronization
+ * approach can't be used here.
+ */
+#define SEM_KEY 0xdeadbeef
 
 /*
  * Default is not to test hugetlbfs
@@ -1333,8 +1350,22 @@ static int sysctl_nested(void *arg)
 
 static int sysctl_nested_wait(void *arg)
 {
-	/* Wait for a SIGCONT. */
-	kill(getpid(), SIGSTOP);
+	int sem = semget(SEM_KEY, 1, 0600);
+	struct sembuf sembuf;
+
+	if (sem < 0) {
+		perror("semget:");
+		abort();
+	}
+	sembuf.sem_num = 0;
+	sembuf.sem_flg = 0;
+	sembuf.sem_op = 0;
+
+	if (semop(sem, &sembuf, 1) < 0) {
+		perror("semop:");
+		abort();
+	}
+
 	return sysctl_nested(arg);
 }
 
@@ -1355,7 +1386,9 @@ static void test_sysctl_sysctl2_failset(void)
 
 static int sysctl_nested_child(void *arg)
 {
-	int pid;
+	int pid, sem;
+	union semun semun;
+	struct sembuf sembuf;
 
 	printf("%s nested sysctl 0\n", memfd_str);
 	sysctl_assert_write("0");
@@ -1389,23 +1422,53 @@ static int sysctl_nested_child(void *arg)
 			   test_sysctl_sysctl2_failset);
 	join_thread(pid);
 
+	sem = semget(SEM_KEY, 1, IPC_CREAT | 0600);
+	if (sem < 0) {
+		perror("semget:");
+		return 1;
+	}
+	semun.val = 1;
+	sembuf.sem_op = -1;
+	sembuf.sem_flg = 0;
+	sembuf.sem_num = 0;
+
 	/* Verify that the rules are actually inherited after fork. */
 	printf("%s nested sysctl 0 -> 1 after fork\n", memfd_str);
 	sysctl_assert_write("0");
 
+	if (semctl(sem, 0, SETVAL, semun) < 0) {
+		perror("semctl:");
+		return 1;
+	}
+
 	pid = spawn_thread(CLONE_NEWPID, sysctl_nested_wait,
 			   test_sysctl_sysctl1_failset);
 	sysctl_assert_write("1");
-	kill(pid, SIGCONT);
+
+	/* Allow child to continue */
+	if (semop(sem, &sembuf, 1) < 0) {
+		perror("semop:");
+		return 1;
+	}
 	join_thread(pid);
 
 	printf("%s nested sysctl 0 -> 2 after fork\n", memfd_str);
 	sysctl_assert_write("0");
 
+	if (semctl(sem, 0, SETVAL, semun) < 0) {
+		perror("semctl:");
+		return 1;
+	}
+
 	pid = spawn_thread(CLONE_NEWPID, sysctl_nested_wait,
 			   test_sysctl_sysctl2_failset);
 	sysctl_assert_write("2");
-	kill(pid, SIGCONT);
+
+	/* Allow child to continue */
+	if (semop(sem, &sembuf, 1) < 0) {
+		perror("semop:");
+		return 1;
+	}
 	join_thread(pid);
 
 	/*
@@ -1415,28 +1478,62 @@ static int sysctl_nested_child(void *arg)
 	 */
 	printf("%s nested sysctl 2 -> 1 after fork\n", memfd_str);
 	sysctl_assert_write("2");
+
+	if (semctl(sem, 0, SETVAL, semun) < 0) {
+		perror("semctl:");
+		return 1;
+	}
+
 	pid = spawn_thread(CLONE_NEWPID, sysctl_nested_wait,
 			   test_sysctl_sysctl2);
 	sysctl_assert_write("1");
-	kill(pid, SIGCONT);
+
+	/* Allow child to continue */
+	if (semop(sem, &sembuf, 1) < 0) {
+		perror("semop:");
+		return 1;
+	}
 	join_thread(pid);
 
 	printf("%s nested sysctl 2 -> 0 after fork\n", memfd_str);
 	sysctl_assert_write("2");
+
+	if (semctl(sem, 0, SETVAL, semun) < 0) {
+		perror("semctl:");
+		return 1;
+	}
+
 	pid = spawn_thread(CLONE_NEWPID, sysctl_nested_wait,
 			   test_sysctl_sysctl2);
 	sysctl_assert_write("0");
-	kill(pid, SIGCONT);
+
+	/* Allow child to continue */
+	if (semop(sem, &sembuf, 1) < 0) {
+		perror("semop:");
+		return 1;
+	}
 	join_thread(pid);
 
 	printf("%s nested sysctl 1 -> 0 after fork\n", memfd_str);
 	sysctl_assert_write("1");
+
+	if (semctl(sem, 0, SETVAL, semun) < 0) {
+		perror("semctl:");
+		return 1;
+	}
+
 	pid = spawn_thread(CLONE_NEWPID, sysctl_nested_wait,
 			   test_sysctl_sysctl1);
 	sysctl_assert_write("0");
-	kill(pid, SIGCONT);
+	/* Allow child to continue */
+	if (semop(sem, &sembuf, 1) < 0) {
+		perror("semop:");
+		return 1;
+	}
 	join_thread(pid);
 
+	semctl(sem, 0, IPC_RMID);
+
 	return 0;
 }