From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932623AbcBZONL (ORCPT ); Fri, 26 Feb 2016 09:13:11 -0500 Received: from mail-pf0-f195.google.com ([209.85.192.195]:32817 "EHLO mail-pf0-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753125AbcBZONK (ORCPT ); Fri, 26 Feb 2016 09:13:10 -0500 Subject: Re: [PATCH v2 1/3] tracing/syscalls: Rename variable 'nr' to 'syscall_nr' To: Arnaldo Carvalho de Melo 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> <20160226134625.GT8720@kernel.org> Cc: Steven Rostedt , Ingo Molnar , Jiri Olsa , Namhyung Kim , linux-kernel@vger.kernel.org, Thomas Gleixner , Lai Jiangshan From: Taeung Song Message-ID: <56D05D70.6070701@gmail.com> Date: Fri, 26 Feb 2016 23:13:04 +0900 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.5.1 MIME-Version: 1.0 In-Reply-To: <20160226134625.GT8720@kernel.org> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 02/26/2016 10:46 PM, Arnaldo Carvalho de Melo wrote: > 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. > I got it. so I sent this change as new patch "[PATCH 2/2] perf trace: Check and discard not only 'nr' but also '__syscall_nr'" to you as below :-) diff --git a/tools/perf/builtin-trace.c b/tools/perf/builtin-trace.c index 20916dd..a252f3a 100644 --- a/tools/perf/builtin-trace.c +++ b/tools/perf/builtin-trace.c @@ -1724,8 +1724,12 @@ static int trace__read_syscall_info(struct trace *trace, int id) sc->args = sc->tp_format->format.fields; sc->nr_args = sc->tp_format->format.nr_fields; - /* drop nr field - not relevant here; does not exist on older kernels */ - if (sc->args && strcmp(sc->args->name, "nr") == 0) { + /* + * We need to check and discard the first variable '__syscall_nr' + * or 'nr' that mean the syscall number. It is needless here. + * So drop '__syscall_nr' or 'nr' field but does not exist on older kernels. + */ + if (sc->args && (!strcmp(sc->args->name, "__syscall_nr") || !strcmp(sc->args->name, "nr"))) { sc->args = sc->args->next; --sc->nr_args; } Thanks, Taeung