[PATCH 6.6.y 2/3] seqlock: Change do_task_stat() to use scoped_seqlock_read()

[Sasha Levin <sashal@kernel.org>]

From: Oleg Nesterov <oleg@redhat.com>

[ Upstream commit b76f72bea2c601afec81829ea427fc0d20f83216 ]

To simplify the code and make it more readable.

[peterz: change to new interface]
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Stable-dep-of: 6650527444da ("proc: protect ptrace_may_access() with exec_update_lock (part 1)")
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 fs/proc/array.c | 9 ++-------
 1 file changed, 2 insertions(+), 7 deletions(-)

diff --git a/fs/proc/array.c b/fs/proc/array.c
index 363d9331216b91..d5cf316f3eb429 100644
--- a/fs/proc/array.c
+++ b/fs/proc/array.c
@@ -483,7 +483,6 @@ static int do_task_stat(struct seq_file *m, struct pid_namespace *ns,
 	unsigned long flags;
 	int exit_code = task->exit_code;
 	struct signal_struct *sig = task->signal;
-	unsigned int seq = 1;
 
 	state = *get_task_state(task);
 	vsize = eip = esp = 0;
@@ -540,10 +539,7 @@ static int do_task_stat(struct seq_file *m, struct pid_namespace *ns,
 	if (permitted && (!whole || num_threads < 2))
 		wchan = !task_is_running(task);
 
-	do {
-		seq++; /* 2 on the 1st/lockless path, otherwise odd */
-		flags = read_seqbegin_or_lock_irqsave(&sig->stats_lock, &seq);
-
+	scoped_seqlock_read (&sig->stats_lock, ss_lock_irqsave) {
 		cmin_flt = sig->cmin_flt;
 		cmaj_flt = sig->cmaj_flt;
 		cutime = sig->cutime;
@@ -565,8 +561,7 @@ static int do_task_stat(struct seq_file *m, struct pid_namespace *ns,
 			}
 			rcu_read_unlock();
 		}
-	} while (need_seqretry(&sig->stats_lock, seq));
-	done_seqretry_irqrestore(&sig->stats_lock, seq, flags);
+	}
 
 	if (whole) {
 		thread_group_cputime_adjusted(task, &utime, &stime);
-- 
2.53.0