linux-kernel - Re: [PATCH] tracing/kprobes: Add trace event trigger invocations

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Message-ID: <20140106111055.2cf828f7@gandalf.local.home>
Date:	Mon, 6 Jan 2014 11:10:55 -0500
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Tom Zanussi <tom.zanussi@...ux.intel.com>
Cc:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	Jean-Jacques Hiblot <jjhiblot@...phandler.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] tracing/kprobes: Add trace event trigger invocations

On Sat, 28 Dec 2013 20:24:08 -0600
Tom Zanussi <tom.zanussi@...ux.intel.com> wrote:

> Add code to the kprobe/kretprobe event functions that will invoke any
> event triggers associated with a probe's ftrace_event_file.
> 
> The code to do this is very similar to the invocation code already
> used to invoke the triggers associated with static events and
> essentially replaces the existing soft-disable checks with a superset
> that preserves the original behavior but adds the bits needed to
> support event triggers.
> 
> Signed-off-by: Tom Zanussi <tom.zanussi@...ux.intel.com>
> ---
>  kernel/trace/trace_kprobe.c | 42 ++++++++++++++++++++++++++++++++++++------
>  1 file changed, 36 insertions(+), 6 deletions(-)
> 
> diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
> index dae9541..1ee13eb 100644
> --- a/kernel/trace/trace_kprobe.c
> +++ b/kernel/trace/trace_kprobe.c
> @@ -812,12 +812,20 @@ __kprobe_trace_func(struct trace_probe *tp, struct pt_regs *regs,
>  	struct ring_buffer *buffer;
>  	int size, dsize, pc;
>  	unsigned long irq_flags;
> +	unsigned long eflags;
> +	enum event_trigger_type __tt = ETT_NONE;

What's the significance of the "__" in the variable?

Looks as if you copied it from the ftrace_raw_event_* macro. The "__"
there is usually recommended because it is a macro and we try to avoid
namespace collisions by adding the "__".

This is a proper function, please remove the "__" from it.

Thanks,

-- Steve


>  	struct ftrace_event_call *call = &tp->call;
>  
>  	WARN_ON(call != ftrace_file->event_call);
>  
> -	if (test_bit(FTRACE_EVENT_FL_SOFT_DISABLED_BIT, &ftrace_file->flags))
> -		return;
> +	eflags = ftrace_file->flags;
> +
> +	if (!(eflags & FTRACE_EVENT_FL_TRIGGER_COND)) {
> +		if (eflags & FTRACE_EVENT_FL_TRIGGER_MODE)
> +			event_triggers_call(ftrace_file, NULL);
> +		if (eflags & FTRACE_EVENT_FL_SOFT_DISABLED)
> +			return;
> +	}
>  
>  	local_save_flags(irq_flags);
>  	pc = preempt_count();
--
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