linux-kernel - [patch 10/19] signal: Move MMCID exit out of sighand lock

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Message-ID: <20251015172834.947237114@linutronix.de>
Date: Wed, 15 Oct 2025 19:29:42 +0200 (CEST)
From: Thomas Gleixner <tglx@...utronix.de>
To: LKML <linux-kernel@...r.kernel.org>
Cc: Peter Zijlstra <peterz@...radead.org>,
 Gabriele Monaco <gmonaco@...hat.com>,
 Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
 Michael Jeanson <mjeanson@...icios.com>,
 Jens Axboe <axboe@...nel.dk>,
 "Paul E. McKenney" <paulmck@...nel.org>,
 "Gautham R. Shenoy" <gautham.shenoy@....com>,
 Florian Weimer <fweimer@...hat.com>,
 Tim Chen <tim.c.chen@...el.com>,
 TCMalloc Team <tcmalloc-eng@...gle.com>
Subject: [patch 10/19] 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@...utronix.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(-)

--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -2290,7 +2290,7 @@ static __always_inline void alloc_tag_re
 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;
@@ -2299,7 +2299,7 @@ static inline int task_mm_cid(struct tas
 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)
 {
 	/*
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -905,6 +905,7 @@ 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);
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -10427,7 +10427,7 @@ static inline void mm_update_cpus_allowe
 	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;
 
@@ -10445,7 +10445,7 @@ void sched_mm_cid_exit_signals(struct ta
 /* 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() */
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -3125,7 +3125,6 @@ void exit_signals(struct task_struct *ts
 	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 *ts
 	 * 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);