From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751155AbbEST64 (ORCPT ); Tue, 19 May 2015 15:58:56 -0400 Received: from mga11.intel.com ([192.55.52.93]:49287 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750865AbbEST6z (ORCPT ); Tue, 19 May 2015 15:58:55 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.13,459,1427785200"; d="scan'208";a="712653556" Message-ID: <555B95F3.9080003@intel.com> Date: Tue, 19 May 2015 22:58:43 +0300 From: Adrian Hunter User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:31.0) Gecko/20100101 Thunderbird/31.6.0 MIME-Version: 1.0 To: Namhyung Kim CC: Arnaldo Carvalho de Melo , linux-kernel@vger.kernel.org, Jiri Olsa Subject: Re: [PATCH 5/5] perf tools: Fix data_read_offset() file opening References: <1432040746-1755-1-git-send-email-adrian.hunter@intel.com> <1432040746-1755-6-git-send-email-adrian.hunter@intel.com> <20150519144818.GA29162@danjae.kornet> In-Reply-To: <20150519144818.GA29162@danjae.kornet> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 19/05/2015 5:48 p.m., Namhyung Kim wrote: > Hi Adrian, > > On Tue, May 19, 2015 at 04:05:46PM +0300, Adrian Hunter wrote: >> Patch "perf tools: Protect dso cache fd with a mutex" >> changed data_file_size() to open the data file if it >> was not open. >> >> data_read_offset() was calling data_file_size() to read >> the data file size, but data_file_size() can fail to >> open the file because the binary_type has not been set up. >> >> The correct function to call is dso__data_size() which >> uses dso__data_fd() to open the file correctly. > > Right, but I worried about the locking overhead. By using > dso__data_size() it'll call dso__data_fd() everytime which grabs the > dso__data_open_lock that is a global mutex. It can be a performance > bottleneck on multi-thread report IMHO. > > I assumed that correct code should check the data fd or size before > calling read function as I read the comment in dso.h file. > > What about adding the missing check in a proper place instead? It looks to me like you need to change data_file_size() and dso_cache__read() so that they open the fd properly i.e. call dso__data_fd() instead of open_dso(). dso__data_fd() should not be taking a lock because the lock must be held while the fd in being used. Perhaps there should be dso__get_fd() and dso__put_fd() that lock/open and the unlock. But I will have to leave this to you because I am snowed with my own problems. > > Thanks, > Namhyung > > >> >> Signed-off-by: Adrian Hunter >> --- >> tools/perf/util/dso.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/tools/perf/util/dso.c b/tools/perf/util/dso.c >> index 1b96c8d..e248f56 100644 >> --- a/tools/perf/util/dso.c >> +++ b/tools/perf/util/dso.c >> @@ -756,7 +756,7 @@ off_t dso__data_size(struct dso *dso, struct machine *machine) >> static ssize_t data_read_offset(struct dso *dso, struct machine *machine, >> u64 offset, u8 *data, ssize_t size) >> { >> - if (data_file_size(dso, machine)) >> + if (dso__data_size(dso, machine) < 0) >> return -1; >> >> /* Check the offset sanity. */ >> -- >> 1.9.1 >>