From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760829AbbA1VgP (ORCPT ); Wed, 28 Jan 2015 16:36:15 -0500 Received: from foss-mx-na.foss.arm.com ([217.140.108.86]:45525 "EHLO foss-mx-na.foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1761444AbbA1UnG (ORCPT ); Wed, 28 Jan 2015 15:43:06 -0500 Date: Wed, 28 Jan 2015 12:24:03 +0000 From: Javi Merino To: Steven Rostedt Cc: "linux-kernel@vger.kernel.org" , Dave P Martin , Ingo Molnar Subject: Re: [PATCH v4 1/3] tracing: Add array printing helpers Message-ID: <20150128122403.GA1542@e104805> References: <1422274311-19738-1-git-send-email-javi.merino@arm.com> <1422274311-19738-2-git-send-email-javi.merino@arm.com> <20150127223557.407f3a13@gandalf.local.home> <20150128112609.GA2938@e104805> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20150128112609.GA2938@e104805> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jan 28, 2015 at 11:26:09AM +0000, Javi Merino wrote: > On Wed, Jan 28, 2015 at 03:35:57AM +0000, Steven Rostedt wrote: > > On Mon, 26 Jan 2015 12:11:49 +0000 > > Javi Merino wrote: > > > > > From: Dave Martin > > > > > > If a trace event contains an array, there is currently no standard > > > way to format this for text output. Drivers are currently hacking > > > around this by a) local hacks that use the trace_seq functionailty > > > directly, or b) just not printing that information. For fixed size > > > arrays, formatting of the elements can be open-coded, but this gets > > > cumbersome for arrays of non-trivial size. > > > > > > These approaches result in non-standard content of the event format > > > description delivered to userspace, so userland tools needs to be > > > taught to understand and parse each array printing method > > > individually. > > > > > > This patch implements common __print__array() helpers that > > > tracepoint implementations can use instead of reinventing them. A > > > simple C-style syntax is used to delimit the array and its elements > > > {like,this}. > > > > > > So that the helpers can be used with large static arrays as well as > > > dynamic arrays, they take a pointer and element count: they can be > > > used with __get_dynamic_array() for use with dynamic arrays. > > > > > > Cc: Steven Rostedt > > > Cc: Ingo Molnar > > > Signed-off-by: Dave Martin > > > Signed-off-by: Javi Merino > > > --- > > > include/linux/ftrace_event.h | 4 ++++ > > > include/trace/ftrace.h | 9 +++++++++ > > > kernel/trace/trace_output.c | 44 ++++++++++++++++++++++++++++++++++++++++++++ > > > 3 files changed, 57 insertions(+) > > > > > > diff --git a/include/linux/ftrace_event.h b/include/linux/ftrace_event.h > > > index 0bebb5c348b8..5aa4a9269547 100644 > > > --- a/include/linux/ftrace_event.h > > > +++ b/include/linux/ftrace_event.h > > > @@ -44,6 +44,10 @@ const char *ftrace_print_bitmask_seq(struct trace_seq *p, void *bitmask_ptr, > > > const char *ftrace_print_hex_seq(struct trace_seq *p, > > > const unsigned char *buf, int len); > > > > > > +const char *ftrace_print_array_seq(struct trace_seq *p, > > > + const void *buf, int buf_len, > > > + size_t el_size); > > > + > > > struct trace_iterator; > > > struct trace_event; > > > > > > diff --git a/include/trace/ftrace.h b/include/trace/ftrace.h > > > index 139b5067345b..36afd0ed3458 100644 > > > --- a/include/trace/ftrace.h > > > +++ b/include/trace/ftrace.h > > > @@ -263,6 +263,14 @@ > > > #undef __print_hex > > > #define __print_hex(buf, buf_len) ftrace_print_hex_seq(p, buf, buf_len) > > > > > > +#undef __print_array > > > +#define __print_array(array, count, el_size) \ > > > + ({ \ > > > + BUILD_BUG_ON(el_size != 8 && el_size != 16 && \ > > > + el_size != 32 && el_size != 64); \ > > > > I tried testing this patch by writing a print_array myself, and I kept > > hitting this BUILD_BUG_ON, and was wondering WTF? Then it dawned on me. > > > > el_size should not be based on bits, it should be based on bytes. I > > passed in "sizeof()" which doesn't work with bits. Ugh. If you use sizeof() in print_array() then trace-cmd won't be able to parse it since it doesn't have an implementation of sizeof(). [thermal_power_allocator:thermal_power_allocator] function sizeof not defined Error: expected type 5 but read 0 *** Error in `./trace-cmd': double free or corruption (fasttop): 0x0000000000e04980 *** Implementing a fully functional sizeof() in trace-cmd will be a huge beast, I guess you will have to limit it to only some types. > > Please update to "el_size < 1 || el_size > 8". > > > > and adjust the rest accordingly. > > Done, I'm testing it now. I'll send a v5 later today. > > Cheers, > Javi