[PATCH 6.7 58/61] exit: wait_task_zombie: kill the no longer necessary spin_lock_irq(siglock)

Sasha Levin
2024-03-13T16:34:12Z

From: Oleg Nesterov <oleg@redhat.com>

[ Upstream commit c1be35a16b2f1fe21f4f26f9de030ad6eaaf6a25 ]

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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
kernel/exit.c | 10 +++-------
1 file changed, 3 insertions(+), 7 deletions(-)

diff --git a/kernel/exit.c b/kernel/exit.c
index aedc0832c9f4d..0c4858581c98c 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -1125,17 +1125,14 @@ 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;
@@ -1158,8 +1155,7 @@ 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)
--
2.43.0