From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755876AbZETBzR (ORCPT ); Tue, 19 May 2009 21:55:17 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755212AbZETBzH (ORCPT ); Tue, 19 May 2009 21:55:07 -0400 Received: from ey-out-2122.google.com ([74.125.78.25]:32099 "EHLO ey-out-2122.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754888AbZETBzE (ORCPT ); Tue, 19 May 2009 21:55:04 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=date:from:to:cc:subject:message-id:references:mime-version :content-type:content-disposition:in-reply-to:user-agent; b=KVFszrm26A9ggTuRCqXmQzq5FUR6RP/ygfanEgQXaaPsjl4caqF0A8GJdiV4RCcE9+ QQZ/L/6hEJ/40FMOqX34Fwpkunvtt0JP3XPIPI0TcOa8MSz278VMT+pg8jtxymKaE97N wqa6h5+VPP+spp8IWJHN7uYAb6DOKEK+SFcfI= Date: Wed, 20 May 2009 03:55:02 +0200 From: Frederic Weisbecker To: Steven Rostedt Cc: LKML , Ingo Molnar , Andrew Morton Subject: Re: [PATCH][GIT PULL] tracing: add trace_stack interface Message-ID: <20090520015501.GI6066@nowhere> References: <20090520010714.GG6066@nowhere> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, May 19, 2009 at 09:14:13PM -0400, Steven Rostedt wrote: > > On Wed, 20 May 2009, Frederic Weisbecker wrote: > > > On Tue, May 19, 2009 at 08:44:50PM -0400, Steven Rostedt wrote: > > > > > > Ingo, > > > > > > Please pull the latest tip/tracing/ftrace tree, which can be found at: > > > > > > git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-2.6-trace.git > > > tip/tracing/ftrace > > > > > > > > > Steven Rostedt (1): > > > tracing: add trace_stack interface > > > > > > ---- > > > include/linux/kernel.h | 2 ++ > > > kernel/trace/trace.c | 15 +++++++++++++++ > > > 2 files changed, 17 insertions(+), 0 deletions(-) > > > --------------------------- > > > commit b85d1029ba534376d203c3ac83a2e5a4d6876cb6 > > > Author: Steven Rostedt > > > Date: Tue May 19 18:54:16 2009 -0400 > > > > > > tracing: add trace_stack interface > > > > > > This patch adds the global function > > > > > > void trace_stack(void) > > > > > > This allows a developer to find where a function is called. For example, > > > if you want to know who calls __netif_reschedule, you can add > > > > > > static inline void __netif_reschedule(struct Qdisc *q) > > > { > > > struct softnet_data *sd; > > > unsigned long flags; > > > > > > + trace_stack(); > > > local_irq_save(flags); > > > sd = &__get_cpu_var(softnet_data); > > > q->next_sched = sd->output_queue; > > > > > > And see the following in the trace output: > > > > > > <= __ftrace_trace_stack > > > <= trace_stack > > > > > > > > I guess the depth should begin here :-) > > Yeah, I thought about that but since it only prints out the stack trace, > this is sorta the "this is a stack trace" header. Indeed :) > > > > > > > > > <= __netif_schedule > > > <= dev_watchdog > > > <= run_timer_softirq > > > <= __do_softirq > > > <= call_softirq > > > <= do_softirq > > > <= irq_exit > > > > > > Signed-off-by: Steven Rostedt > > > > > > diff --git a/include/linux/kernel.h b/include/linux/kernel.h > > > index 883cd44..347a0f1 100644 > > > --- a/include/linux/kernel.h > > > +++ b/include/linux/kernel.h > > > @@ -511,6 +511,7 @@ extern int > > > __ftrace_vprintk(unsigned long ip, const char *fmt, va_list ap); > > > > > > extern void ftrace_dump(void); > > > +extern void trace_stack(void); > > > #else > > > static inline void > > > ftrace_special(unsigned long arg1, unsigned long arg2, unsigned long arg3) { } > > > @@ -531,6 +532,7 @@ ftrace_vprintk(const char *fmt, va_list ap) > > > return 0; > > > } > > > static inline void ftrace_dump(void) { } > > > +static inline void trace_stack(void) { } > > > #endif /* CONFIG_TRACING */ > > > > > > /* > > > diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c > > > index dd40d23..33ab502 100644 > > > --- a/kernel/trace/trace.c > > > +++ b/kernel/trace/trace.c > > > @@ -1046,6 +1046,21 @@ void __trace_stack(struct trace_array *tr, > > > __ftrace_trace_stack(tr, flags, skip, pc); > > > } > > > > > > +/** > > > + * trace_stack - dump the stack into the trace buffer > > > + * > > > + * Use this to record the stack trace into the ring buffer. If you > > > + * want to know a caller of a function, place a call to trace_stack > > > + * and the ftrace trace file will display who the callers were. > > > + */ > > > +void trace_stack(void) > > > +{ > > > + unsigned long flags; > > > + > > > + local_save_flags(flags); > > > + __trace_stack(&global_trace, flags, 0, preempt_count()); > > > +} > > > > > > > > Stupidly I use a very similar patch while working on reiserfs > > but I forgot to post it. > > > > Another trick is to use trace_printk() combined with: > > > > echo stacktrace > trace_option > > Yeah, but when you are debugging development work, doing that at every > boot up becomes a pain. You can add it to a rc script but still. Right! > I wrote this because of the development I'm doing in the interrupt > threads. I was using this a lot to find what is calling what. > > -- Steve >