From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752452AbcA2GgM (ORCPT ); Fri, 29 Jan 2016 01:36:12 -0500 Received: from mail-pa0-f65.google.com ([209.85.220.65]:33631 "EHLO mail-pa0-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751717AbcA2GgL (ORCPT ); Fri, 29 Jan 2016 01:36:11 -0500 Date: Fri, 29 Jan 2016 15:37:24 +0900 From: Sergey Senozhatsky To: Peter Hurley Cc: Sergey Senozhatsky , Sergey Senozhatsky , Byungchul Park , akpm@linux-foundation.org, mingo@kernel.org, linux-kernel@vger.kernel.org, akinobu.mita@gmail.com, jack@suse.cz, torvalds@linux-foundation.org Subject: Re: [PATCH v4] lib/spinlock_debug.c: prevent a recursive cycle in the debug code Message-ID: <20160129063656.GF4820@swordfish> References: <20160128081313.GB31266@X58A-UD3R> <20160128104137.GA610@swordfish> <20160128105342.GB610@swordfish> <20160128154257.GA564@swordfish> <56AA9F63.9070600@hurleysoftware.com> <20160129002703.GA4820@swordfish> <56AAEB50.8050801@hurleysoftware.com> <20160129052838.GD4820@swordfish> <56AAFD41.5020005@hurleysoftware.com> <20160129061653.GE4820@swordfish> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20160129061653.GE4820@swordfish> 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 On (01/29/16 15:16), Sergey Senozhatsky wrote: > > http://marc.info/?l=linux-kernel&m=144976121529901 > hm... I don't like that patch. ->reset() loop must be done outside of zap_locks(). we can have a printk() recursion in CPU1, but console driver lock may be owned by CPU2 in driver's handle_IRQ(), for example. stealing its lock CPU1 is not really good. in my kernels I do this from panic() path only, where I know that things are already bad. panic()->console_panic_mode()->{for_each_console()->reset(), zap_locks()}->console_trelock()->console_unlock(). -ss