Re: [RESEND PATCH 5.10] fs/proc: do_task_stat: use __for_each_thread()

[Greg KH <gregkh@linuxfoundation.org>]

On Thu, Jul 10, 2025 at 12:35:43PM +0000, Heyne, Maximilian wrote:
> From: Oleg Nesterov <oleg@redhat.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@redhat.com>
> Cc: Eric W. Biederman <ebiederm@xmission.com>
> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
> Stable-dep-of: 7601df8031fd ("fs/proc: do_task_stat: use sig->stats_lock to gather the threads/children stats")
> Cc: stable@vger.kernel.org
> [mheyne: adjusted context]
> Signed-off-by: Maximilian Heyne <mheyne@amazon.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").

And this fixes it?

How?

> 
> ---
>  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 8fba6d39e776..77b94c04e4af 100644
> --- a/fs/proc/array.c
> +++ b/fs/proc/array.c
> @@ -512,18 +512,18 @@ 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);
> +			}

Ideally, the code generated here should be identical as before, so why
is this change needed?

confused,

greg k-h