linux-kernel - Re: [PATCH 1/5] jump label: notifier atomic call chain notrace

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Date:	Mon, 22 Mar 2010 13:55:04 -0400
From:	Masami Hiramatsu <mhiramat@...hat.com>
To:	Jason Baron <jbaron@...hat.com>
CC:	linux-kernel@...r.kernel.org, mingo@...e.hu,
	mathieu.desnoyers@...ymtl.ca, hpa@...or.com, tglx@...utronix.de,
	rostedt@...dmis.org, andi@...stfloor.org, roland@...hat.com,
	rth@...hat.com, fweisbec@...il.com
Subject: Re: [PATCH 1/5] jump label: notifier atomic call chain notrace

Jason Baron wrote:
> From: Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
> 
> In LTTng, being able to use the atomic notifier from cpu idle entry to
> ensure the tracer flush the last events in the current subbuffer
> requires the rcu read-side to be marked "notrace", otherwise it can end
> up calling back into lockdep and the tracer.
> 
> Also apply to the the die notifier.

Looks good for me and it'll be good for kprobe-tracer too:)


> 
> Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
> Signed-off-by: Jason Baron <jbaron@...hat.com>

Reviewed-by: Masami Hiramatsu <mhiramat@...hat.com>

> ---
>  kernel/notifier.c |    6 +++---
>  1 files changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/kernel/notifier.c b/kernel/notifier.c
> index 2488ba7..88453a7 100644
> --- a/kernel/notifier.c
> +++ b/kernel/notifier.c
> @@ -148,7 +148,7 @@ int atomic_notifier_chain_unregister(struct atomic_notifier_head *nh,
>  	spin_lock_irqsave(&nh->lock, flags);
>  	ret = notifier_chain_unregister(&nh->head, n);
>  	spin_unlock_irqrestore(&nh->lock, flags);
> -	synchronize_rcu();
> +	synchronize_sched();
>  	return ret;
>  }
>  EXPORT_SYMBOL_GPL(atomic_notifier_chain_unregister);
> @@ -178,9 +178,9 @@ int __kprobes __atomic_notifier_call_chain(struct atomic_notifier_head *nh,
>  {
>  	int ret;
>  
> -	rcu_read_lock();
> +	rcu_read_lock_sched_notrace();
>  	ret = notifier_call_chain(&nh->head, val, v, nr_to_call, nr_calls);
> -	rcu_read_unlock();
> +	rcu_read_unlock_sched_notrace();
>  	return ret;
>  }
>  EXPORT_SYMBOL_GPL(__atomic_notifier_call_chain);

-- 
Masami Hiramatsu
e-mail: mhiramat@...hat.com
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