linux-kernel - Re: [PATCH tip/core/rcu 2/3] rcu: Add missing annotation for exit_tasks_rcu

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Date:   Mon, 17 Feb 2020 09:44:52 -0500
From:   Joel Fernandes <joel@...lfernandes.org>
To:     paulmck@...nel.org
Cc:     rcu@...r.kernel.org, linux-kernel@...r.kernel.org,
        kernel-team@...com, mingo@...nel.org, jiangshanlai@...il.com,
        dipankar@...ibm.com, akpm@...ux-foundation.org,
        mathieu.desnoyers@...icios.com, josh@...htriplett.org,
        tglx@...utronix.de, peterz@...radead.org, rostedt@...dmis.org,
        dhowells@...hat.com, edumazet@...gle.com, fweisbec@...il.com,
        oleg@...hat.com, Jules Irenge <jbi.octave@...il.com>
Subject: Re: [PATCH tip/core/rcu 2/3] rcu: Add missing annotation for
 exit_tasks_rcu_start()

On Fri, Feb 14, 2020 at 04:25:19PM -0800, paulmck@...nel.org wrote:
> From: Jules Irenge <jbi.octave@...il.com>
> 
> Sparse reports a warning at exit_tasks_rcu_start(void)
> 
> |warning: context imbalance in exit_tasks_rcu_start() - wrong count at exit
> 
> To fix this, this commit adds an __acquires(&tasks_rcu_exit_srcu).
> Given that exit_tasks_rcu_start() does actually call __srcu_read_lock(),
> this not only fixes the warning but also improves on the readability of
> the code.

For patch 1/3 and 2/3:

Reviewed-by: Joel Fernandes (Google) <joel@...lfernandes.org>

Though IMO it would be good to squash both the patches.

thanks,

 - Joel


> Signed-off-by: Jules Irenge <jbi.octave@...il.com>
> Signed-off-by: Paul E. McKenney <paulmck@...nel.org>
> ---
>  kernel/rcu/update.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/kernel/rcu/update.c b/kernel/rcu/update.c
> index a27df76..a04fe54 100644
> --- a/kernel/rcu/update.c
> +++ b/kernel/rcu/update.c
> @@ -801,7 +801,7 @@ static int __init rcu_spawn_tasks_kthread(void)
>  core_initcall(rcu_spawn_tasks_kthread);
>  
>  /* Do the srcu_read_lock() for the above synchronize_srcu().  */
> -void exit_tasks_rcu_start(void)
> +void exit_tasks_rcu_start(void) __acquires(&tasks_rcu_exit_srcu)
>  {
>  	preempt_disable();
>  	current->rcu_tasks_idx = __srcu_read_lock(&tasks_rcu_exit_srcu);
> -- 
> 2.9.5
>