Question about task_struct::state

Question about task_struct::state

[Dhaval Giani]

Hi Ingo, Oleg,

sched.h has a comment in task_struct

        volatile long state;    /* -1 unrunnable, 0 runnable, >0 stopped */

After some searching, I've not been able to figure out how state can
become -1 (or unrunnable). Can you let me know how that happens?

If it cannot reach that state, then maybe this patch is needed.

Signed-off-by: Dhaval Giani <dhaval@linux.vnet.ibm.com>

Index: linux-2.6/include/linux/sched.h
===================================================================
--- linux-2.6.orig/include/linux/sched.h	2008-06-10 21:13:02.000000000 +0530
+++ linux-2.6/include/linux/sched.h	2008-06-10 21:14:44.000000000 +0530
@@ -1024,7 +1024,7 @@ struct sched_rt_entity {
 };
 
 struct task_struct {
-	volatile long state;	/* -1 unrunnable, 0 runnable, >0 stopped */
+	volatile long state;	/* 0 runnable, >0 stopped */
 	void *stack;
 	atomic_t usage;
 	unsigned int flags;	/* per process flags, defined below */

-- 
regards,
Dhaval

Re: Question about task_struct::state

[Oleg Nesterov]

On 06/10, Dhaval Giani wrote:
> 
> sched.h has a comment in task_struct
> 
>         volatile long state;    /* -1 unrunnable, 0 runnable, >0 stopped */
> 
> After some searching, I've not been able to figure out how state can
> become -1 (or unrunnable). Can you let me know how that happens?
> 
> If it cannot reach that state, then maybe this patch is needed.
> 
> Signed-off-by: Dhaval Giani <dhaval@linux.vnet.ibm.com>
> 
> Index: linux-2.6/include/linux/sched.h
> ===================================================================
> --- linux-2.6.orig/include/linux/sched.h	2008-06-10 21:13:02.000000000 +0530
> +++ linux-2.6/include/linux/sched.h	2008-06-10 21:14:44.000000000 +0530
> @@ -1024,7 +1024,7 @@ struct sched_rt_entity {
>  };
>  
>  struct task_struct {
> -	volatile long state;	/* -1 unrunnable, 0 runnable, >0 stopped */
> +	volatile long state;	/* 0 runnable, >0 stopped */

I think you are right, the comment is wrong (obsolete?).

Perhaps it is better to just remove it, or add a note about TASK_RUNNING/etc
above. ">0 stopped" looks a bit confusing too.

I'd suggest you to change the subject and send the patch to Andrew.

Oleg.