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

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Message-ID: <20200217231045.GA2935@paulmck-ThinkPad-P72>
Date:   Mon, 17 Feb 2020 15:10:45 -0800
From:   "Paul E. McKenney" <paulmck@...nel.org>
To:     Joel Fernandes <joel@...lfernandes.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 Mon, Feb 17, 2020 at 09:44:52AM -0500, Joel Fernandes wrote:
> 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>

Applied, thank you!

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

Fair point, but I will leave them be.  ;-)

							Thanx, Paul

> 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
> >