linux-kernel - [tip: locking/core] seqlock: Change do_task_stat() to use scoped_seqlock

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Message-ID: <176104292132.2601451.5637554410583858580.tip-bot2@tip-bot2>
Date: Tue, 21 Oct 2025 10:35:21 -0000
From: "tip-bot2 for Oleg Nesterov" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: Oleg Nesterov <oleg@...hat.com>,
 "Peter Zijlstra (Intel)" <peterz@...radead.org>, x86@...nel.org,
 linux-kernel@...r.kernel.org
Subject: [tip: locking/core] seqlock: Change do_task_stat() to use
 scoped_seqlock_read()

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

Commit-ID:     b76f72bea2c601afec81829ea427fc0d20f83216
Gitweb:        https://git.kernel.org/tip/b76f72bea2c601afec81829ea427fc0d20f83216
Author:        Oleg Nesterov <oleg@...hat.com>
AuthorDate:    Wed, 08 Oct 2025 14:30:59 +02:00
Committer:     Peter Zijlstra <peterz@...radead.org>
CommitterDate: Tue, 21 Oct 2025 12:31:57 +02:00

seqlock: Change do_task_stat() to use scoped_seqlock_read()

To simplify the code and make it more readable.

[peterz: change to new interface]
Signed-off-by: Oleg Nesterov <oleg@...hat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.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 2ae6318..cbd4bc4 100644
--- a/fs/proc/array.c
+++ b/fs/proc/array.c
@@ -481,7 +481,6 @@ 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;
@@ -538,10 +537,7 @@ 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;
@@ -563,8 +559,7 @@ 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);