linux-kernel - Re: [PATCH 3/3] tracing: Protect ftrace_trace_arrays list in trace

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Message-ID: <1372728304.22688.32.camel@gandalf.local.home>
Date:	Mon, 01 Jul 2013 21:25:04 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Alexander Z Lam <azl@...gle.com>
Cc:	linux-kernel@...r.kernel.org, David Sharp <dhsharp@...gle.com>,
	Vaibhav Nagarnaik <vnagarnaik@...gle.com>,
	Alexander Z Lam <lambchop468@...il.com>
Subject: Re: [PATCH 3/3] tracing: Protect ftrace_trace_arrays list in
 trace_events.c

On Mon, 2013-07-01 at 15:31 -0700, Alexander Z Lam wrote:
> There are multiple places where the ftrace_trace_arrays list is accessed in
> trace_events.c without the trace_types_lock held.

Hmm, doesn't compile. Not a complete patch? trace_types_lock is local to
trace.c, and needs to be in trace.h and non static.

-- Steve

> 
> Cc: David Sharp <dhsharp@...gle.com>
> Cc: Alexander Z Lam <lambchop468@...il.com>
> Signed-off-by: Alexander Z Lam <azl@...gle.com>
> ---
>  kernel/trace/trace_events.c | 9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)
> 
> diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
> index 6db3290..26351cc 100644
> --- a/kernel/trace/trace_events.c
> +++ b/kernel/trace/trace_events.c
> @@ -1586,6 +1586,7 @@ static void __add_event_to_tracers(struct ftrace_event_call *call,
>  int trace_add_event_call(struct ftrace_event_call *call)
>  {
>  	int ret;
> +	mutex_lock(&trace_types_lock);
>  	mutex_lock(&event_mutex);
>  
>  	ret = __register_event(call, NULL);
> @@ -1593,11 +1594,13 @@ int trace_add_event_call(struct ftrace_event_call *call)
>  		__add_event_to_tracers(call, NULL);
>  
>  	mutex_unlock(&event_mutex);
> +	mutex_unlock(&trace_types_lock);
>  	return ret;
>  }
>  
>  /*
> - * Must be called under locking both of event_mutex and trace_event_sem.
> + * Must be called under locking of trace_types_lock, event_mutex and
> + * trace_event_sem.
>   */
>  static void __trace_remove_event_call(struct ftrace_event_call *call)
>  {
> @@ -1609,11 +1612,13 @@ static void __trace_remove_event_call(struct ftrace_event_call *call)
>  /* Remove an event_call */
>  void trace_remove_event_call(struct ftrace_event_call *call)
>  {
> +	mutex_lock(&trace_types_lock);
>  	mutex_lock(&event_mutex);
>  	down_write(&trace_event_sem);
>  	__trace_remove_event_call(call);
>  	up_write(&trace_event_sem);
>  	mutex_unlock(&event_mutex);
> +	mutex_unlock(&trace_types_lock);
>  }
>  
>  #define for_each_event(event, start, end)			\
> @@ -1757,6 +1762,7 @@ static int trace_module_notify(struct notifier_block *self,
>  {
>  	struct module *mod = data;
>  
> +	mutex_lock(&trace_types_lock);
>  	mutex_lock(&event_mutex);
>  	switch (val) {
>  	case MODULE_STATE_COMING:
> @@ -1767,6 +1773,7 @@ static int trace_module_notify(struct notifier_block *self,
>  		break;
>  	}
>  	mutex_unlock(&event_mutex);
> +	mutex_unlock(&trace_types_lock);
>  
>  	return 0;
>  }


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