From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760414AbcBYJpH (ORCPT ); Thu, 25 Feb 2016 04:45:07 -0500 Received: from mail-pa0-f49.google.com ([209.85.220.49]:33509 "EHLO mail-pa0-f49.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751434AbcBYJpD (ORCPT ); Thu, 25 Feb 2016 04:45:03 -0500 Date: Thu, 25 Feb 2016 18:46:21 +0900 From: Sergey Senozhatsky To: Petr Mladek Cc: Jan Kara , Peter Zijlstra , Steven Rostedt , Andrew Morton , Ingo Molnar , linux-kernel@vger.kernel.org, Sergey Senozhatsky , Sergey Senozhatsky Subject: [linux-next, x86_64] no backtrace after "printk/nmi: generic solution for safe printk in NMI" Message-ID: <20160225094621.GA505@swordfish> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline 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 Hello Petr, seem that commit b927968830676373caf4241e80d8b447133f84b2 Author: Petr Mladek Date: Thu Feb 25 13:00:35 2016 +1100 printk/nmi: generic solution for safe printk in NMI printk() takes some locks and could not be used a safe way in NMI context. The chance of a deadlock is real especially when printing stacks from all CPUs. This particular problem has been addressed on x86 by the commit a9edc8809328 ("x86/nmi: Perform a safe NMI stack trace on all CPUs"). The patchset brings two big advantages. First, it makes the NMI backtraces safe on all architectures for free. Second, it makes all NMI messages almost safe on all architectures (the temporary buffer is limited. We still should keep the number of messages in NMI context at minimum). [..] makes my x86_64 boxen unhappy, I see no CPU backtraces and no panic messages on HARDLOCKUPs (CONFIG_BOOTPARAM_HARDLOCKUP_PANIC_VALUE=1). does it work for you? -ss