[PATCH RT] sched: drop is_special_task_state() check from __set_current_state_no_track()

[PATCH RT] sched: drop is_special_task_state() check from __set_current_state_no_track()

[Sebastian Andrzej Siewior]

The is_special_task_state() check in __set_current_state_no_track()
has been wrongly placed. __set_current_state_no_track() is used in RT
while a sleeping lock is acquired. It is used at the begin of the wait
loop with TASK_UNINTERRUPTIBLE and while leaving it and restoring the
original state. The latter part triggers the warning.

Drop the special state check. This is only used within the sleeping lock
implementation and the assignment happens while the PI lock is held.
While at it, drop set_current_state_no_track() because it has no users.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
 include/linux/sched.h | 8 --------
 1 file changed, 8 deletions(-)

diff --git a/include/linux/sched.h b/include/linux/sched.h
index a0c1c0cae992..b20264e17b02 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -132,16 +132,9 @@ struct task_group;
 
 #define __set_current_state_no_track(state_value)		\
 	do {							\
-		WARN_ON_ONCE(is_special_task_state(state_value));\
 		current->state = (state_value);			\
 	} while (0)
 
-#define set_current_state_no_track(state_value)			\
-	do {							\
-		WARN_ON_ONCE(is_special_task_state(state_value));\
-		smp_store_mb(current->state, (state_value));	\
-	} while (0)
-
 #define set_special_state(state_value)					\
 	do {								\
 		unsigned long flags; /* may shadow */			\
@@ -196,7 +189,6 @@ struct task_group;
 	smp_store_mb(current->state, (state_value))
 
 #define __set_current_state_no_track(state_value)	__set_current_state(state_value)
-#define set_current_state_no_track(state_value)		set_current_state(state_value)
 
 /*
  * set_special_state() should be used for those states when the blocking task
-- 
2.18.0

Re: [PATCH RT] sched: drop is_special_task_state() check from __set_current_state_no_track()

[Steven Rostedt]

On Wed, 1 Aug 2018 11:05:25 +0200
Sebastian Andrzej Siewior <bigeasy@linutronix.de> wrote:

> The is_special_task_state() check in __set_current_state_no_track()
> has been wrongly placed. __set_current_state_no_track() is used in RT
> while a sleeping lock is acquired. It is used at the begin of the wait
> loop with TASK_UNINTERRUPTIBLE and while leaving it and restoring the
> original state. The latter part triggers the warning.
> 
> Drop the special state check. This is only used within the sleeping lock
> implementation and the assignment happens while the PI lock is held.
> While at it, drop set_current_state_no_track() because it has no users.
> 
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
> ---
>  include/linux/sched.h | 8 --------
>  1 file changed, 8 deletions(-)
> 
> diff --git a/include/linux/sched.h b/include/linux/sched.h
> index a0c1c0cae992..b20264e17b02 100644
> --- a/include/linux/sched.h
> +++ b/include/linux/sched.h
> @@ -132,16 +132,9 @@ struct task_group;
>  
>  #define __set_current_state_no_track(state_value)		\
>  	do {							\
> -		WARN_ON_ONCE(is_special_task_state(state_value));\
>  		current->state = (state_value);			\
>  	} while (0)

I don't think we need to keep the do { } while with a single line. It
is now equivalent to the non-debug version of __set_current_state()
which is defined as:

#define __set_current_state(state_value)				\
	current->state = (state_value)

-- Steve

>  
> -#define set_current_state_no_track(state_value)			\
> -	do {							\
> -		WARN_ON_ONCE(is_special_task_state(state_value));\
> -		smp_store_mb(current->state, (state_value));	\
> -	} while (0)
> -
>  #define set_special_state(state_value)					\
>  	do {								\
>  		unsigned long flags; /* may shadow */			\
> @@ -196,7 +189,6 @@ struct task_group;
>  	smp_store_mb(current->state, (state_value))
>  
>  #define __set_current_state_no_track(state_value)	__set_current_state(state_value)
> -#define set_current_state_no_track(state_value)		set_current_state(state_value)
>  
>  /*
>   * set_special_state() should be used for those states when the blocking task

Re: [PATCH RT] sched: drop is_special_task_state() check from __set_current_state_no_track()

[Sebastian Andrzej Siewior]

On 2018-08-01 09:19:42 [-0400], Steven Rostedt wrote:
> I don't think we need to keep the do { } while with a single line. It
> is now equivalent to the non-debug version of __set_current_state()
> which is defined as:
> 
> #define __set_current_state(state_value)				\
> 	current->state = (state_value)

okay.

> -- Steve

Sebastian