From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756203AbZLCOPY (ORCPT ); Thu, 3 Dec 2009 09:15:24 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755297AbZLCOPX (ORCPT ); Thu, 3 Dec 2009 09:15:23 -0500 Received: from hrndva-omtalb.mail.rr.com ([71.74.56.124]:37770 "EHLO hrndva-omtalb.mail.rr.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751535AbZLCOPW (ORCPT ); Thu, 3 Dec 2009 09:15:22 -0500 Subject: Re: [PATCH] Fix tracing infrastructure to support multiple includes when defining CREATE_TRACE_POINTS From: Steven Rostedt Reply-To: rostedt@goodmis.org To: Neil Horman Cc: linux-kernel@vger.kernel.org, fweisbec@gmail.com, mingo@redhat.com, Mathieu Desnoyers In-Reply-To: <20091202191916.GA7589@hmsreliant.think-freely.org> References: <20091202191916.GA7589@hmsreliant.think-freely.org> Content-Type: text/plain Organization: Kihon Technologies Inc. Date: Thu, 03 Dec 2009 09:15:26 -0500 Message-Id: <1259849726.12870.123.camel@gandalf.stny.rr.com> Mime-Version: 1.0 X-Mailer: Evolution 2.26.3 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 2009-12-02 at 14:19 -0500, Neil Horman wrote: > Fix tracing infrastructure to allow multiple header files with TRACE_EVENTS to > be included with CREATE_TRACE_EVENTS defined > > I've been workingon adding a few tracepoints to the network stack, and in so > doing it was convienient for me to add a second include file to > net/core/net-traces.c with TRACE_EVENTS defined in them. net-traces.c defines > CREATE_TRACE_EVENTS, and during the build it was failing, complaining about > duplicate definitions of __tpstrtab_. I tracked down the bug to find that > define_trace.h redefined DECLARE_TRACE to be DEFINE_TRACE, so after the first > run through define_trace.h (which is included from skb.h, included in > net-trace.c first), the DECLARE_TRACE macro was left with an improper definition > to start a new cycle with the next header. > > The fix I came up with was to make sure that DECLARE_TRACE was undefined at the > end of define_trace.h, and to add a conditional re-definition in tracepoint.h. > This places us back in the proper state to define a new set of tracepoints in a > subsequent header file. Not sure if theres a better way to handle this, but > this worked well for me, allowing me to include multiple headers with > TRACE_EVENT macros in a c file with CREATE_TRACE_POINTS defined. > Nice, just some comments below. > Signed-off-by: Neil Horman > > > linux/tracepoint.h | 18 ++++++++++++++++++ > trace/define_trace.h | 1 + > 2 files changed, 19 insertions(+) > > diff --git a/include/linux/tracepoint.h b/include/linux/tracepoint.h > index 2aac8a8..562d8ba 100644 > --- a/include/linux/tracepoint.h > +++ b/include/linux/tracepoint.h > @@ -173,6 +173,24 @@ static inline void tracepoint_synchronize_unregister(void) > * trace event headers under one "CREATE_TRACE_POINTS" the first include > * will override the TRACE_EVENT and break the second include. > */ > +#ifndef DECLARE_TRACE > +#define DECLARE_TRACE(name, proto, args) \ > + extern struct tracepoint __tracepoint_##name; \ > + static inline void trace_##name(proto) \ > + { \ > + if (unlikely(__tracepoint_##name.state)) \ > + __DO_TRACE(&__tracepoint_##name, \ > + TP_PROTO(proto), TP_ARGS(args)); \ > + } \ > + static inline int register_trace_##name(void (*probe)(proto)) \ > + { \ > + return tracepoint_probe_register(#name, (void *)probe); \ > + } \ > + static inline int unregister_trace_##name(void (*probe)(proto)) \ > + { \ > + return tracepoint_probe_unregister(#name, (void *)probe);\ > + } > +#endif > You duplicate the DECLARE_TRACE from above and place it into an unprotected area. Why not move it instead of duplicating it. This is just a bug waiting to happen if we ever need to modify DECLARE_TRACE. If you change it to: #if !defined(CONFIG_TRACEPOINTS) && !defined(DECLARE_TRACE) #define DECLARE_TRACE(...) .... #endif Then you can remove the first definition of it. The first time processing the file, when it hits the #ifndef DECLARE_TRACE in the _LINUX_TRACEPOINT_H conditional, it still does not define DECLARE_TRACE, and then when it exits that conditional, it does. -- Steve > #ifndef TRACE_EVENT > /* > diff --git a/include/trace/define_trace.h b/include/trace/define_trace.h > index 2a4b3bf..a3e0095 100644 > --- a/include/trace/define_trace.h > +++ b/include/trace/define_trace.h > @@ -64,6 +64,7 @@ > #undef TRACE_EVENT > #undef TRACE_EVENT_FN > #undef TRACE_HEADER_MULTI_READ > +#undef DECLARE_TRACE > > /* Only undef what we defined in this file */ > #ifdef UNDEF_TRACE_INCLUDE_FILE