linux-kernel - Re: [RFC][PATCH 3/3] lockdep,trace: Expose tracepoints

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Date:   Fri, 7 Aug 2020 16:34:22 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     tglx@...utronix.de, mingo@...nel.org, will@...nel.org,
        x86@...nel.org, linux-kernel@...r.kernel.org, elver@...gle.com,
        paulmck@...nel.org, rjw@...ysocki.net
Subject: Re: [RFC][PATCH 3/3] lockdep,trace: Expose tracepoints

On Fri, 07 Aug 2020 21:23:39 +0200
Peter Zijlstra <peterz@...radead.org> wrote:

> The lockdep tracepoints are under the lockdep recursion counter, this
> has a bunch of nasty side effects:
> 
>  - TRACE_IRQFLAGS doesn't work across the entire tracepoint, leading to
>    all sorts of dodgy complaints.
> 
>  - RCU-lockdep doesn't see the tracepoints either, hiding numerous
>    "suspicious RCU usage" warnings.
> 
> Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
> ---
>  kernel/locking/lockdep.c |   27 ++++++++++++++++++---------
>  1 file changed, 18 insertions(+), 9 deletions(-)
> 
> --- a/kernel/locking/lockdep.c
> +++ b/kernel/locking/lockdep.c
> @@ -5000,8 +5000,9 @@ void lock_acquire(struct lockdep_map *lo
>  	raw_local_irq_save(flags);
>  	check_flags(flags);
>  
> -	current->lockdep_recursion++;
>  	trace_lock_acquire(lock, subclass, trylock, read, check, nest_lock, ip);
> +
> +	current->lockdep_recursion++;
>  	__lock_acquire(lock, subclass, trylock, read, check,
>  		       irqs_disabled_flags(flags), nest_lock, ip, 0, 0);
>  	lockdep_recursion_finish();
> @@ -5016,10 +5017,13 @@ void lock_release(struct lockdep_map *lo
>  	if (unlikely(current->lockdep_recursion))
>  		return;
>  
> +

Superfluous space.
 

Other than that:

Reviewed-by: Steven Rosted (VMware) <rostedt@...dmis.org>

-- Steve

>  	raw_local_irq_save(flags);
>  	check_flags(flags);
> -	current->lockdep_recursion++;
> +
>  	trace_lock_release(lock, ip);
> +
> +	current->lockdep_recursion++;
>  	if (__lock_release(lock, ip))
>  		check_chain_key(current);
>  	lockdep_recursion_finish();
> @@ -5171,7 +5175,7 @@ __lock_contended(struct lockdep_map *loc
>  		stats->bounces[bounce_contended + !!hlock->read]++;
>  }
>