From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754172AbcBZNqb (ORCPT ); Fri, 26 Feb 2016 08:46:31 -0500 Received: from mail.kernel.org ([198.145.29.136]:37932 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750922AbcBZNqa (ORCPT ); Fri, 26 Feb 2016 08:46:30 -0500 Date: Fri, 26 Feb 2016 10:46:25 -0300 From: Arnaldo Carvalho de Melo To: Taeung Song Cc: Arnaldo Carvalho de Melo , Steven Rostedt , Ingo Molnar , Jiri Olsa , Namhyung Kim , linux-kernel@vger.kernel.org, Thomas Gleixner , Lai Jiangshan Subject: Re: [PATCH v2 1/3] tracing/syscalls: Rename variable 'nr' to 'syscall_nr' Message-ID: <20160226134625.GT8720@kernel.org> References: <1456421937-16840-1-git-send-email-treeze.taeung@gmail.com> <20160225175710.GP8720@kernel.org> <56CF4877.8000107@gmail.com> <20160225184234.GQ8720@kernel.org> <56D0440E.1000605@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <56D0440E.1000605@gmail.com> X-Url: http://acmel.wordpress.com User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Em Fri, Feb 26, 2016 at 09:24:46PM +0900, Taeung Song escreveu: > Hi, Arnaldo > > On 02/26/2016 03:42 AM, Arnaldo Carvalho de Melo wrote: > >Em Fri, Feb 26, 2016 at 03:31:19AM +0900, Taeung Song escreveu: > >>Hi, Arnaldo > >> > >>On 02/26/2016 02:57 AM, Arnaldo Carvalho de Melo wrote: > >>>Em Fri, Feb 26, 2016 at 02:38:57AM +0900, Taeung Song escreveu: > >>>>There is a problem about duplicated variable name i.e. > >>>> # cat /sys/kernel/debug/tracing/events/syscalls/sys_enter_io_getevents/format > >>>> name: sys_enter_io_getevents > >>>> ID: 739 > >>>> format: > >>>> field:unsigned short common_type; offset:0; size:2; signed:0; > >>>> field:unsigned char common_flags; offset:2; size:1; signed:0; > >>>> field:unsigned char common_preempt_count; offset:3; size:1; signed:0; > >>>> field:int common_pid;offset:4;size:4;signed:1; > >>>> field:int nr; offset:8; size:4; signed:1; > >>>> field:aio_context_t ctx_id; offset:16; size:8; signed:0; > >>>> field:long min_nr; offset:24; size:8; signed:0; > >>>> field:long nr; offset:32; size:8; signed:0; > >>>> field:struct io_event * events; offset:40; size:8; signed:0; > >>>> field:struct timespec * timeout; offset:48; size:8; signed:0; > >>>> > >>>> print fmt: "ctx_id: 0x%08lx, min_nr: 0x%08lx, nr: 0x%08lx, > >>>> events: 0x%08lx, timeout: 0x%08lx", ((unsigned long)(REC->ctx_id)), > >>>> ((unsigned long)(REC->min_nr)), ((unsigned long)(REC->nr)), > >>>> ((unsigned long)(REC->events)), ((unsigned long)(REC->timeout)) > >>>> > >>>>As above 'int nr;' and 'long nr;' variables have > >>>>duplicated name so problems are occurred in perf-script i.e. > >>>> > >>>> # perf record -e syscalls:* > >>>> # perf script -g python > >>>> # perf script -s perf-script.py > >>>> File "perf-script.py", line 8694 > >>>> def syscalls__sys_enter_io_getevents(event_name, context, common_cpu, > >>>> SyntaxError: duplicate argument 'nr' in function definition > >>>> Error running python script perf-script.py > >>> > >>>Please test this with 'perf trace', which this patch breaks, this patch > >>>should make it understand this 3rd variation of the non common list of > >>>fields in syscall tracepoints: > >> > >>OK, I will test it. > >>But IMHO, I think the bottom change has a problem. > >>Because sys_enter_io_getevent() has a argument 'long nr'. > > > >It doesn't matter > > > >>So this if statement must not have strcmp(sc->args->name, "nr") == 0. > > > >This is checking for the first variable, if that has that name, it > >should be discarded, as in the past it wasn't there, so for the tool to > >work on kernels with "nr" as the first (for the syscall number) variable > >and for kernels without it, we must check and discard. > > > >Now we must check and discard the first "nr" (for kernels with this > >meaning the syscall number) and also if it is called "syscall_nr"). > >The other fields are taken as the syscall arguments, in the order that > >they come, that is what what we will match with what is in the > >raw_syscalls:sys_enter args array: > > > >[root@jouet ~]# cat > >/sys/kernel/debug/tracing/events/raw_syscalls/sys_enter/format > >name: sys_enter > >ID: 17 > >format: > > field:unsigned short common_type; offset:0; size:2; signed:0; > > field:unsigned char common_flags; offset:2; size:1; signed:0; > > field:unsigned char common_preempt_count; offset:3; size:1; signed:0; > > field:int common_pid; offset:4; size:4; signed:1; > > > > field:long id; offset:8; size:8; signed:1; > > field:unsigned long args[6]; offset:16; size:48; signed:0; > > > >print fmt: "NR %ld (%lx, %lx, %lx, %lx, %lx, %lx)", REC->id, > >REC->args[0], REC->args[1], REC->args[2], REC->args[3], REC->args[4], > >REC->args[5] > >[root@jouet ~]# > > > >>+ if (sc->args && strcmp(sc->args->name, "syscall_nr") == 0) { > >> > >>I think the above instance seem better than the bottom. > >> > >>+ if (sc->args && (strcmp(sc->args->name, "syscall_nr") || > >>strcmp(sc->args->name, "nr")) == 0) { > > > >Right in this 'if' body we do: > > > > sc->args = sc->args->next; > > sc->nr_args--; > > > >something like that. > > > >- Arnaldo > > > >>But I'll test again with perf-trace. > > > >Right, look at the output of 'perf trace' before and after, so that you > >can check if, say, we're using that syscall_nr value as the fd for the > >'write' syscall ('fd' comes right after 'nr'/'syscall_nr'). > > > > Sorry, I'm late. > > I tested perf-trace with the bottom change. > (does not rename it to '__syscall_nr' on kernel) "With this change:" > > + if (sc->args && (strcmp(sc->args->name, "__syscall_nr") || > strcmp(sc->args->name, "nr")) == 0) { > sc->args = sc->args->next; > --sc->nr_args; > } > > But there are some problems as below. Right, there is a silly error, we have to test both strcmp(), checking if one of them is equal to zero, i.e. if there was a match. - Arnaldo > 0.322 ( 0.012 ms): a.out/27045 write(nr: 3, fd: 4196046, buf: 0x4, count: > 2140 ) = 4 > > So, I modified the above change. (I'll send it as new patch) > And then I tested again as below > > 0.345 ( 0.016 ms): a.out/27695 write(fd: 3, buf: 0x4006ce, count: 4 ) = 4 > > And I tested perf-trace with renamed '__syscall_nr' on modified kernel. > Everything is ok for aught I know. > > 0.345 ( 0.016 ms): a.out/27695 write(fd: 3, buf: 0x4006ce, count: 4 ) = 4 > > I'm writing another patchset. I'll send it soon. > > Thanks, > Taeung