exit: wait_task_zombie: kill the no longer necessary spin_lock_irq(siglock)

After the recent changes nobody use siglock to read the values protected
by stats_lock, we can kill spin_lock_irq(&current->sighand->siglock) and
update the comment.

With this patch only __exit_signal() and thread_group_start_cputime() take
stats_lock under siglock.

Link: https://lkml.kernel.org/r/20240123153359.GA21866@redhat.com
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Dylan Hatch <dylanbhatch@google.com>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/kernel/exit.c b/kernel/exit.c
index 3988a02efaef06444654a415ce298d378ab925ec..dfb963d2f862ada6a2f06259c6df4923272cb218 100644 (file)
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -1127,17 +1127,14 @@ static int wait_task_zombie(struct wait_opts *wo, struct task_struct *p)
                 * and nobody can change them.
                 *
                 * psig->stats_lock also protects us from our sub-threads
-                * which can reap other children at the same time. Until
-                * we change k_getrusage()-like users to rely on this lock
-                * we have to take ->siglock as well.
+                * which can reap other children at the same time.
                 *
                 * We use thread_group_cputime_adjusted() to get times for
                 * the thread group, which consolidates times for all threads
                 * in the group including the group leader.
                 */
                thread_group_cputime_adjusted(p, &tgutime, &tgstime);
-               spin_lock_irq(&current->sighand->siglock);
-               write_seqlock(&psig->stats_lock);
+               write_seqlock_irq(&psig->stats_lock);
                psig->cutime += tgutime + sig->cutime;
                psig->cstime += tgstime + sig->cstime;
                psig->cgtime += task_gtime(p) + sig->gtime + sig->cgtime;
@@ -1160,8 +1157,7 @@ static int wait_task_zombie(struct wait_opts *wo, struct task_struct *p)
                        psig->cmaxrss = maxrss;
                task_io_accounting_add(&psig->ioac, &p->ioac);
                task_io_accounting_add(&psig->ioac, &sig->ioac);
-               write_sequnlock(&psig->stats_lock);
-               spin_unlock_irq(&current->sighand->siglock);
+               write_sequnlock_irq(&psig->stats_lock);
        }
 
        if (wo->wo_rusage)