[PATCH -mm 1/2] proc_sched_show_task: use get_nr_threads()

[PATCH -mm 1/2] proc_sched_show_task: use get_nr_threads()

[Oleg Nesterov]

Trivial, use get_nr_threads() helper to read signal->count which
we are going to change.

Like other callers, proc_sched_show_task() doesn't need the exactly
precise nr_threads.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
---

 kernel/sched_debug.c |   10 ++--------
 1 file changed, 2 insertions(+), 8 deletions(-)

--- 34-rc1/kernel/sched_debug.c~MISC_1_PROC_SCHED_SHOW_TASK	2009-12-18 19:05:38.000000000 +0100
+++ 34-rc1/kernel/sched_debug.c	2010-03-23 14:52:42.000000000 +0100
@@ -384,15 +384,9 @@ __initcall(init_sched_debug_procfs);
 void proc_sched_show_task(struct task_struct *p, struct seq_file *m)
 {
 	unsigned long nr_switches;
-	unsigned long flags;
-	int num_threads = 1;
-
-	if (lock_task_sighand(p, &flags)) {
-		num_threads = atomic_read(&p->signal->count);
-		unlock_task_sighand(p, &flags);
-	}
 
-	SEQ_printf(m, "%s (%d, #threads: %d)\n", p->comm, p->pid, num_threads);
+	SEQ_printf(m, "%s (%d, #threads: %d)\n", p->comm, p->pid,
+						get_nr_threads(p));
 	SEQ_printf(m,
 		"---------------------------------------------------------\n");
 #define __P(F) \

Re: [PATCH -mm 1/2] proc_sched_show_task: use get_nr_threads()

[Oleg Nesterov]

On 03/23, Oleg Nesterov wrote:
>
> Trivial, use get_nr_threads() helper to read signal->count which
> we are going to change.
>
> Like other callers, proc_sched_show_task() doesn't need the exactly
> precise nr_threads.

I don't think this can make any problem, but let me clarify just in
case to avoid the possible confusion...

This change is not equivalent. Before this patch, num_threads == 1
if p has already exited (no matter how many other threads we have).

After this patch, we always report the correct number of live threads
in this thread group, this also means we can report zero in unlikely
case.

> Signed-off-by: Oleg Nesterov <oleg@redhat.com>
> ---
> 
>  kernel/sched_debug.c |   10 ++--------
>  1 file changed, 2 insertions(+), 8 deletions(-)
> 
> --- 34-rc1/kernel/sched_debug.c~MISC_1_PROC_SCHED_SHOW_TASK	2009-12-18 19:05:38.000000000 +0100
> +++ 34-rc1/kernel/sched_debug.c	2010-03-23 14:52:42.000000000 +0100
> @@ -384,15 +384,9 @@ __initcall(init_sched_debug_procfs);
>  void proc_sched_show_task(struct task_struct *p, struct seq_file *m)
>  {
>  	unsigned long nr_switches;
> -	unsigned long flags;
> -	int num_threads = 1;
> -
> -	if (lock_task_sighand(p, &flags)) {
> -		num_threads = atomic_read(&p->signal->count);
> -		unlock_task_sighand(p, &flags);
> -	}
>  
> -	SEQ_printf(m, "%s (%d, #threads: %d)\n", p->comm, p->pid, num_threads);
> +	SEQ_printf(m, "%s (%d, #threads: %d)\n", p->comm, p->pid,
> +						get_nr_threads(p));
>  	SEQ_printf(m,
>  		"---------------------------------------------------------\n");
>  #define __P(F) \

Re: [PATCH -mm 1/2] proc_sched_show_task: use get_nr_threads()

[David Howells]

Oleg Nesterov <oleg@redhat.com> wrote:

> Trivial, use get_nr_threads() helper to read signal->count which
> we are going to change.
> 
> Like other callers, proc_sched_show_task() doesn't need the exactly
> precise nr_threads.

Note that get_nr_threads() isn't completely equivalent (it can return 0 where
proc_sched_show_task() will display a 1).  But I don't think this should be a
problem.

> Signed-off-by: Oleg Nesterov <oleg@redhat.com>

Acked-by: David Howells <dhowells@redhat.com>

Re: [PATCH -mm 1/2] proc_sched_show_task: use get_nr_threads()

[Roland McGrath]

Acked-by: Roland McGrath <roland@redhat.com>


Thanks,
Roland