From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756046Ab1GJMI1 (ORCPT ); Sun, 10 Jul 2011 08:08:27 -0400 Received: from mail7.hitachi.co.jp ([133.145.228.42]:59026 "EHLO mail7.hitachi.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755932Ab1GJMI0 (ORCPT ); Sun, 10 Jul 2011 08:08:26 -0400 X-AuditID: b753bd60-a507fba0000050a4-63-4e1996367a61 X-AuditID: b753bd60-a507fba0000050a4-63-4e1996367a61 Message-ID: <4E199633.9050200@hitachi.com> Date: Sun, 10 Jul 2011 21:08:19 +0900 From: Masami Hiramatsu Organization: Systems Development Lab., Hitachi, Ltd., Japan User-Agent: Mozilla/5.0 (Windows NT 5.1; rv:5.0) Gecko/20110624 Thunderbird/5.0 MIME-Version: 1.0 To: Pekka Enberg Cc: Arnaldo Carvalho de Melo , Ingo Molnar , Frederic Weisbecker , Peter Zijlstra , linux-kernel@vger.kernel.org, yrl.pp-manager.tt@hitachi.com, Masami Hiramatsu , Peter Zijlstra , Paul Mackerras , Arnaldo Carvalho de Melo Subject: Re: [PATCH -tip 4/5] [BUGFIX] perf probe: Fix the order of searching scopes for variables References: <20110710100005.2550.83138.stgit@fedora15> <20110710100033.2550.78762.stgit@fedora15> In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Brightmail-Tracker: AAAAAA== Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Pekka, (2011/07/10 20:05), Pekka Enberg wrote: > On Sun, Jul 10, 2011 at 1:00 PM, Masami Hiramatsu > wrote: >> Fix variable searching routine to search from inner scope >> to outer scope. > > Admittedly, I don't really know this code at all. However, the > changelog is somewhat vague. Why do we need this change? What problem > does it fix? Why does the order in which we iterate 'scopes' matter? Hmm, I see. Debuginfo expresses functions and nested inlined functions as DIE(Dwarf Information Entry) tree, and "scope" means each level of the DIE. Outer ^ | CU DIE [A](compile unit: it's an object file) +-global variable DIEs +-inline function declaration DIEs +-function [B] DIE +-local variable DIEs +-inline function instance [C] DIE +-inline local variable DIEs +-(nested)inline function instance [D] DIE +... | v Inner Imagine that if we are at [C], nscopes = dwarf_getscopes_die([C], &scopes) this returns scopes[] DIEs containing [C] DIE, and nscopes = 3 On that array, scopes[0] is [C], scopes[1] is [B], and scopes[2] is [A]. And, the below loop while (nscopes-- > 1) die_find_variable_at(&scopes[nscopes], ... starts to find variables from the outermost scope [A] and find a global variable first.　This changes searching order from inner scope ([B]) to outer ([A]) to search global vars last. Thank you! > >> Signed-off-by: Masami Hiramatsu >> Cc: Peter Zijlstra >> Cc: Paul Mackerras >> Cc: Ingo Molnar >> Cc: Arnaldo Carvalho de Melo >> --- >> >> tools/perf/util/probe-finder.c | 14 +++++++------- >> 1 files changed, 7 insertions(+), 7 deletions(-) >> >> diff --git a/tools/perf/util/probe-finder.c b/tools/perf/util/probe-finder.c >> index 222ba66..cf7d48d 100644 >> --- a/tools/perf/util/probe-finder.c >> +++ b/tools/perf/util/probe-finder.c >> @@ -1135,7 +1135,7 @@ static int find_variable(Dwarf_Die *sp_die, struct probe_finder *pf) >> { >> Dwarf_Die vr_die, *scopes; >> char buf[32], *ptr; >> - int ret, nscopes; >> + int ret, nscopes, i; >> >> if (!is_c_varname(pf->pvar->var)) { >> /* Copy raw parameters */ >> @@ -1179,11 +1179,11 @@ static int find_variable(Dwarf_Die *sp_die, struct probe_finder *pf) >> /* Search upper class */ >> nscopes = dwarf_getscopes_die(sp_die, &scopes); >> ret = -ENOENT; >> - while (nscopes-- > 1) { >> + for (i = 1; i < nscopes; i++) { /* scopes[0] is sp_die */ >> pr_debug("Searching variables in %s\n", >> - dwarf_diename(&scopes[nscopes])); >> + dwarf_diename(&scopes[i])); >> /* We should check this scope, so give dummy address */ >> - if (die_find_variable_at(&scopes[nscopes], >> + if (die_find_variable_at(&scopes[i], >> pf->pvar->var, 0, >> &vr_die)) { >> ret = convert_variable(&vr_die, pf); >> @@ -1693,7 +1693,7 @@ static int add_available_vars(Dwarf_Die *sp_die, struct probe_finder *pf) >> container_of(pf, struct available_var_finder, pf); >> struct variable_list *vl; >> Dwarf_Die die_mem, *scopes = NULL; >> - int ret, nscopes; >> + int ret, nscopes, i; >> >> /* Check number of tevs */ >> if (af->nvls == af->max_vls) { >> @@ -1723,8 +1723,8 @@ static int add_available_vars(Dwarf_Die *sp_die, struct probe_finder *pf) >> /* Don't need to search child DIE for externs. */ >> af->child = false; >> nscopes = dwarf_getscopes_die(sp_die, &scopes); >> - while (nscopes-- > 1) >> - die_find_child(&scopes[nscopes], collect_variables_cb, >> + for (i = 1; i < nscopes; i++) /* scopes[0] is sp_die */ >> + die_find_child(&scopes[i], collect_variables_cb, >> (void *)af, &die_mem); >> if (scopes) >> free(scopes); >> >> -- >> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in >> the body of a message to majordomo@vger.kernel.org >> More majordomo info at http://vger.kernel.org/majordomo-info.html >> Please read the FAQ at http://www.tux.org/lkml/ >> > -- Masami HIRAMATSU Software Platform Research Dept. Linux Technology Center Hitachi, Ltd., Yokohama Research Laboratory E-mail: masami.hiramatsu.pt@hitachi.com