Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755154Ab3C3F2a (ORCPT ); Sat, 30 Mar 2013 01:28:30 -0400 Received: from alvesta.synopsys.com ([198.182.60.77]:49391 "EHLO alvesta.synopsys.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754960Ab3C3F22 (ORCPT ); Sat, 30 Mar 2013 01:28:28 -0400 Message-ID: <515677DB.4070803@synopsys.com> Date: Sat, 30 Mar 2013 10:57:55 +0530 From: Vineet Gupta User-Agent: Mozilla/5.0 (X11; Linux i686; rv:17.0) Gecko/20130308 Thunderbird/17.0.4 MIME-Version: 1.0 To: Tejun Heo CC: , , , , , , , , , , , , , , , , , , , , , , , , , , , , Heiko Carstens , , Mike Frysinger , Subject: Re: [PATCH 3/5] dump_stack: consolidate dump_stack() implementations and unify their behaviors References: <1364610428-2074-1-git-send-email-tj@kernel.org> <1364610428-2074-4-git-send-email-tj@kernel.org> In-Reply-To: <1364610428-2074-4-git-send-email-tj@kernel.org> X-Enigmail-Version: 1.5.1 Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.12.197.41] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3083 Lines: 71 On 03/30/2013 07:57 AM, Tejun Heo wrote: > Both dump_stack() and show_stack() are currently implemented by each > architecture. show_stack(NULL, NULL) dumps the backtrace for the > current task as does dump_stack(). On some archs, dump_stack() prints > extra information - pid, utsname and so on - in addition to the > backtrace while the two are identical on other archs. > > The usages in arch-independent code of the two functions indicate > show_stack(NULL, NULL) should print out bare backtrace while > dump_stack() is used for debugging purposes when something went wrong, > so it does make sense to print additional information on the task > which triggered dump_stack(). > > There's no reason to require archs to implement two separate but > mostly identical functions. It leads to unnecessary subtle > differences among archs and makes it very tedius to add generic debug > information. > > This patch expands the dummy fallback dump_stack() implementation in > lib/dump_stack.c such that it prints out debug information (taken from > x86) and invokes show_stack(NULL, NULL) and drops arch-specific > dump_stack() implementations in all archs except blackfin and s390. > Blackfin's dump_stack() does something wonky that I don't understand > and s390 prints its own debug information which includes fields which > aren't accessible from arch-indepdent code. > > Debug information can be printed separately by calling > dump_stack_print_info() so that arch-specific dump_stack() > implementation can still emit the same debug information. This is > used in blackfin. > > This patch brings the following behavior changes. > > * On some archs, an extra level in backtrace for show_stack() could be > printed. This is because the top frame was determined in > dump_stack() on those archs while generic dump_stack() can't do that > reliably. It can be compensated by inlining dump_stack() but not > sure whether that'd be necessary. > > * Most archs didn't use to print debug info on dump_stack(). They do > now. > > An example WARN dump follows. > > WARNING: at /work/os/work/kernel/workqueue.c:4840 init_workqueues+0x35/0x505() > Hardware name: empty > Modules linked in: > Pid: 1, comm: swapper/0 Not tainted 3.9.0-rc1-work+ #17 > 0000000000000009 ffff88007c861e08 ffffffff81c61545 ffff88007c861e48 > ffffffff8108f50f ffffffff82228240 0000000000000040 ffffffff8234a03c > 0000000000000000 0000000000000000 0000000000000000 ffff88007c861e58 > Call Trace: > [] dump_stack+0x19/0x1b > [] warn_slowpath_common+0x7f/0xc0 > [] warn_slowpath_null+0x1a/0x20 > [] init_workqueues+0x35/0x505 > ... > > Signed-off-by: Tejun Heo For arch/arc bits Acked-by: Vineet Gupta Thx, -Vineet -- 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/