linux-kernel - Re: [RFC][PATCH 06/18 v2] ftrace: Add rcu_unsafe_filter

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Date:	Sat, 31 Aug 2013 12:46:39 -0700
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Jiri Olsa <jolsa@...hat.com>
Subject: Re: [RFC][PATCH 06/18 v2] ftrace: Add rcu_unsafe_filter_functions
 file

On Sat, Aug 31, 2013 at 01:11:23AM -0400, Steven Rostedt wrote:
> From: "Steven Rostedt (Red Hat)" <rostedt@...dmis.org>
> 
> Since the RCU unsafe functions are no longer displayed by the
> available_filter_functions, we still need a way to see these
> functions in order to trace them. Create a new file that lists
> the functions that were declared RCU unsafe.
> 
> Cc: Jiri Olsa <jolsa@...hat.com>
> Cc: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
> Signed-off-by: Steven Rostedt <rostedt@...dmis.org>

Acked-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>

> ---
>  include/linux/ftrace.h |    1 +
>  kernel/trace/ftrace.c  |   31 +++++++++++++++++++++++++++++++
>  2 files changed, 32 insertions(+)
> 
> diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
> index 4709264..4752764 100644
> --- a/include/linux/ftrace.h
> +++ b/include/linux/ftrace.h
> @@ -412,6 +412,7 @@ enum {
>  	FTRACE_ITER_HASH	= (1 << 4),
>  	FTRACE_ITER_ENABLED	= (1 << 5),
>  	FTRACE_ITER_NO_UNSAFE	= (1 << 6),
> +	FTRACE_ITER_UNSAFE_ONLY	= (1 << 7),
>  };
> 
>  void arch_ftrace_update_code(int command);
> diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
> index be87ac9..a3e4b71 100644
> --- a/kernel/trace/ftrace.c
> +++ b/kernel/trace/ftrace.c
> @@ -2647,6 +2647,9 @@ t_next(struct seq_file *m, void *v, loff_t *pos)
>  		    ((iter->flags & FTRACE_ITER_ENABLED) &&
>  		     !(rec->flags & FTRACE_FL_ENABLED)) ||
> 
> +		    ((iter->flags & FTRACE_ITER_UNSAFE_ONLY) &&
> +		     !ftrace_lookup_ip(ftrace_unsafe_rcu, rec->ip)) ||
> +
>  		    ((iter->flags & FTRACE_ITER_NO_UNSAFE) &&
>  		     ftrace_lookup_ip(ftrace_unsafe_rcu, rec->ip))) {
> 
> @@ -2784,6 +2787,24 @@ ftrace_avail_open(struct inode *inode, struct file *file)
>  }
> 
>  static int
> +ftrace_rcu_unsafe_open(struct inode *inode, struct file *file)
> +{
> +	struct ftrace_iterator *iter;
> +
> +	if (unlikely(ftrace_disabled))
> +		return -ENODEV;
> +
> +	iter = __seq_open_private(file, &show_ftrace_seq_ops, sizeof(*iter));
> +	if (iter) {
> +		iter->pg = ftrace_pages_start;
> +		iter->flags = FTRACE_ITER_UNSAFE_ONLY;
> +		iter->ops = &global_ops;
> +	}
> +
> +	return iter ? 0 : -ENOMEM;
> +}
> +
> +static int
>  ftrace_enabled_open(struct inode *inode, struct file *file)
>  {
>  	struct ftrace_iterator *iter;
> @@ -3835,6 +3856,13 @@ static const struct file_operations ftrace_avail_fops = {
>  	.release = seq_release_private,
>  };
> 
> +static const struct file_operations ftrace_rcu_unsafe_fops = {
> +	.open = ftrace_rcu_unsafe_open,
> +	.read = seq_read,
> +	.llseek = seq_lseek,
> +	.release = seq_release_private,
> +};
> +
>  static const struct file_operations ftrace_enabled_fops = {
>  	.open = ftrace_enabled_open,
>  	.read = seq_read,
> @@ -4071,6 +4099,9 @@ static __init int ftrace_init_dyn_debugfs(struct dentry *d_tracer)
>  	trace_create_file("available_filter_functions", 0444,
>  			d_tracer, NULL, &ftrace_avail_fops);
> 
> +	trace_create_file("rcu_unsafe_filter_functions", 0444,
> +			d_tracer, NULL, &ftrace_rcu_unsafe_fops);
> +
>  	trace_create_file("enabled_functions", 0444,
>  			d_tracer, NULL, &ftrace_enabled_fops);
> 
> -- 
> 1.7.10.4
> 
> 

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