linux-kernel - [PATCH 5.15] fs/proc: do_task_stat: use __for_each

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Message-ID: <20250605-monty-tee-7cec3e1e@mheyne-amazon>
Date: Thu, 5 Jun 2025 14:07:47 +0000
From: "Heyne, Maximilian" <mheyne@...zon.de>
CC: "Heyne, Maximilian" <mheyne@...zon.de>, Oleg Nesterov <oleg@...hat.com>,
	"Eric W. Biederman" <ebiederm@...ssion.com>, Andrew Morton
	<akpm@...ux-foundation.org>, "Sauerwein, David" <dssauerw@...zon.de>, "Sasha
 Levin" <sashal@...nel.org>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>, "linux-fsdevel@...r.kernel.org"
	<linux-fsdevel@...r.kernel.org>
Subject: [PATCH 5.15] fs/proc: do_task_stat: use __for_each_thread()

From: Oleg Nesterov <oleg@...hat.com>

[ Upstream commit 7904e53ed5a20fc678c01d5d1b07ec486425bb6a ]

do/while_each_thread should be avoided when possible.

Link: https://lkml.kernel.org/r/20230909164501.GA11581@redhat.com
Signed-off-by: Oleg Nesterov <oleg@...hat.com>
Cc: Eric W. Biederman <ebiederm@...ssion.com>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Stable-dep-of: 7601df8031fd ("fs/proc: do_task_stat: use sig->stats_lock to gather the threads/children stats")
[mheyne: adjusted context]
Signed-off-by: Maximilian Heyne <mheyne@...zon.de>
---

Compile-tested only.
We're seeing soft lock-ups with 5.10.237 because of the backport of
commit 4fe85bdaabd6 ("fs/proc: do_task_stat: use sig->stats_lock to
gather the threads/children stats"). I'm assuming this is broken on 5.15
too.

---
 fs/proc/array.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/fs/proc/array.c b/fs/proc/array.c
index 2cb01aaa67187..2ff568dc58387 100644
--- a/fs/proc/array.c
+++ b/fs/proc/array.c
@@ -530,18 +530,18 @@ static int do_task_stat(struct seq_file *m, struct pid_namespace *ns,
 		cgtime = sig->cgtime;
 
 		if (whole) {
-			struct task_struct *t = task;
+			struct task_struct *t;
 
 			min_flt = sig->min_flt;
 			maj_flt = sig->maj_flt;
 			gtime = sig->gtime;
 
 			rcu_read_lock();
-			do {
+			__for_each_thread(sig, t) {
 				min_flt += t->min_flt;
 				maj_flt += t->maj_flt;
 				gtime += task_gtime(t);
-			} while_each_thread(task, t);
+			}
 			rcu_read_unlock();
 		}
 	} while (need_seqretry(&sig->stats_lock, seq));
-- 
2.47.1




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