[tip: core/rseq] signal: Move MMCID exit out of sighand lock

["tip-bot2 for Thomas Gleixner" <tip-bot2@linutronix.de>]

The following commit has been merged into the core/rseq branch of tip:

Commit-ID:     1497ac189541df3c7c344bca723a7597009a99f4
Gitweb:        https://git.kernel.org/tip/1497ac189541df3c7c344bca723a7597009a99f4
Author:        Thomas Gleixner <tglx@linutronix.de>
AuthorDate:    Wed, 19 Nov 2025 18:27:05 +01:00
Committer:     Peter Zijlstra <peterz@infradead.org>
CommitterDate: Thu, 20 Nov 2025 12:14:55 +01:00

signal: Move MMCID exit out of sighand lock

There is no need anymore to keep this under sighand lock as the current
code and the upcoming replacement are not depending on the exit state of a
task anymore.

That allows to use a mutex in the exit path.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Link: https://patch.msgid.link/20251119172549.706439391@linutronix.de
---
 include/linux/sched.h | 4 ++--
 kernel/exit.c         | 1 +
 kernel/sched/core.c   | 4 ++--
 kernel/signal.c       | 2 --
 4 files changed, 5 insertions(+), 6 deletions(-)

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 64f080d..c411ae0 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -2298,7 +2298,7 @@ static __always_inline void alloc_tag_restore(struct alloc_tag *tag, struct allo
 void sched_mm_cid_before_execve(struct task_struct *t);
 void sched_mm_cid_after_execve(struct task_struct *t);
 void sched_mm_cid_fork(struct task_struct *t);
-void sched_mm_cid_exit_signals(struct task_struct *t);
+void sched_mm_cid_exit(struct task_struct *t);
 static inline int task_mm_cid(struct task_struct *t)
 {
 	return t->mm_cid.cid;
@@ -2307,7 +2307,7 @@ static inline int task_mm_cid(struct task_struct *t)
 static inline void sched_mm_cid_before_execve(struct task_struct *t) { }
 static inline void sched_mm_cid_after_execve(struct task_struct *t) { }
 static inline void sched_mm_cid_fork(struct task_struct *t) { }
-static inline void sched_mm_cid_exit_signals(struct task_struct *t) { }
+static inline void sched_mm_cid_exit(struct task_struct *t) { }
 static inline int task_mm_cid(struct task_struct *t)
 {
 	/*
diff --git a/kernel/exit.c b/kernel/exit.c
index 9f74e8f..324616f 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -910,6 +910,7 @@ void __noreturn do_exit(long code)
 	user_events_exit(tsk);
 
 	io_uring_files_cancel();
+	sched_mm_cid_exit(tsk);
 	exit_signals(tsk);  /* sets PF_EXITING */
 
 	seccomp_filter_release(tsk);
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 9a114b6..3fdf90a 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -10392,7 +10392,7 @@ static inline void mm_update_cpus_allowed(struct mm_struct *mm, const struct cpu
 	WRITE_ONCE(mm->mm_cid.nr_cpus_allowed, weight);
 }
 
-void sched_mm_cid_exit_signals(struct task_struct *t)
+void sched_mm_cid_exit(struct task_struct *t)
 {
 	struct mm_struct *mm = t->mm;
 
@@ -10410,7 +10410,7 @@ void sched_mm_cid_exit_signals(struct task_struct *t)
 /* Deactivate MM CID allocation across execve() */
 void sched_mm_cid_before_execve(struct task_struct *t)
 {
-	sched_mm_cid_exit_signals(t);
+	sched_mm_cid_exit(t);
 }
 
 /* Reactivate MM CID after successful execve() */
diff --git a/kernel/signal.c b/kernel/signal.c
index fe9190d..e42b8bd 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -3125,7 +3125,6 @@ void exit_signals(struct task_struct *tsk)
 	cgroup_threadgroup_change_begin(tsk);
 
 	if (thread_group_empty(tsk) || (tsk->signal->flags & SIGNAL_GROUP_EXIT)) {
-		sched_mm_cid_exit_signals(tsk);
 		tsk->flags |= PF_EXITING;
 		cgroup_threadgroup_change_end(tsk);
 		return;
@@ -3136,7 +3135,6 @@ void exit_signals(struct task_struct *tsk)
 	 * From now this task is not visible for group-wide signals,
 	 * see wants_signal(), do_signal_stop().
 	 */
-	sched_mm_cid_exit_signals(tsk);
 	tsk->flags |= PF_EXITING;
 
 	cgroup_threadgroup_change_end(tsk);