[tip: timers/core] posix-cpu-timers: Don't abuse lock_task_sighand() in handle_posix_cpu_timers()

[tip-bot2 for Oleg Nesterov]

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

Commit-ID:     a73d7f98e41a96d6e1bcb0e731ab185d9d67878e
Gitweb:        https://git.kernel.org/tip/a73d7f98e41a96d6e1bcb0e731ab185d9d67878e
Author:        Oleg Nesterov <oleg@xxxxxxxxxx>
AuthorDate:    Sat, 04 Jul 2026 13:09:36 +02:00
Committer:     Thomas Gleixner <tglx@xxxxxxxxxx>
CommitterDate: Sun, 05 Jul 2026 12:15:22 +02:00

posix-cpu-timers: Don't abuse lock_task_sighand() in handle_posix_cpu_timers()

After commit f90fff1e152d ("posix-cpu-timers: fix race between
handle_posix_cpu_timers() and posix_cpu_timer_del()"), tsk->sighand is
stable in handle_posix_cpu_timers(), so it can use the plain
spin_lock_irqsave(&tsk->sighand->siglock).

Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxx>
Reviewed-by: Bradley Morgan <include@xxxxxxxxx>
Link: https://patch.msgid.link/akjp8AGpY8eJG5I1@xxxxxxxxxx
---
 kernel/time/posix-cpu-timers.c |  9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/kernel/time/posix-cpu-timers.c b/kernel/time/posix-cpu-timers.c
index 5e633d8..c8a9b52 100644
--- a/kernel/time/posix-cpu-timers.c
+++ b/kernel/time/posix-cpu-timers.c
@@ -1300,8 +1300,11 @@ static void handle_posix_cpu_timers(struct task_struct *tsk)
 	unsigned long flags, start;
 	LIST_HEAD(firing);
 
-	if (!lock_task_sighand(tsk, &flags))
-		return;
+	/*
+	 * tsk is current and ->sighand is stable, see the
+	 * tsk->exit_state check in run_posix_cpu_timers()
+	 */
+	spin_lock_irqsave(&tsk->sighand->siglock, flags);
 
 	do {
 		/*
@@ -1361,7 +1364,7 @@ static void handle_posix_cpu_timers(struct task_struct *tsk)
 	 * that gets the timer lock before we do will give it up and
 	 * spin until we've taken care of that timer below.
 	 */
-	unlock_task_sighand(tsk, &flags);
+	spin_unlock_irqrestore(&tsk->sighand->siglock, flags);
 
 	/*
 	 * Now that all the timers on our list have the firing flag,