Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754569Ab0F2Iwo (ORCPT ); Tue, 29 Jun 2010 04:52:44 -0400 Received: from devils.ext.ti.com ([198.47.26.153]:57028 "EHLO devils.ext.ti.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754550Ab0F2Iwm convert rfc822-to-8bit (ORCPT ); Tue, 29 Jun 2010 04:52:42 -0400 From: "Shilimkar, Santosh" To: Kevin Cernekee CC: "linux-kernel@vger.kernel.org" , Russell King - ARM Linux Date: Tue, 29 Jun 2010 14:22:26 +0530 Subject: Additional fix : (was [v2]printk: fix delayed messages from CPU hotplug events) Thread-Topic: Additional fix : (was [v2]printk: fix delayed messages from CPU hotplug events) Thread-Index: AcsXaGXicqa8+43jSDSUdKePtrVn0A== Message-ID: Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: acceptlanguage: en-US Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 8BIT MIME-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2034 Lines: 58 Hi, I have faced similar issue as what is being described in below with latest kernel. ------------------------------------------------ https://patchwork.kernel.org/patch/103347/ When a secondary CPU is being brought up, it is not uncommon for printk() to be invoked when cpu_online(smp_processor_id()) == 0. The case that I witnessed personally was on MIPS: http://lkml.org/lkml/2010/5/30/4 If (can_use_console() == 0), printk() will spool its output to log_buf and it will be visible in "dmesg", but that output will NOT be echoed to the console until somebody calls release_console_sem() from a CPU that is online. Therefore, the boot time messages from the new CPU can get stuck in "limbo" for a long time, and might suddenly appear on the screen when a completely unrelated event (e.g. "eth0: link is down") occurs. This patch modifies the console code so that any pending messages are automatically flushed out to the console whenever a CPU hotplug operation completes successfully or aborts. ----------------------------------------------- Above patch fixes only half of the problem. I mean the cpu online path prints are coming on the console. But similar problem also exist if there are prints in the cpu offline path. I got that fixed by adding below patch on top of you patch. diff --git a/kernel/printk.c b/kernel/printk.c index d370b74..f4d7352 100644 --- a/kernel/printk.c +++ b/kernel/printk.c @@ -982,6 +982,9 @@ static int __cpuinit console_cpu_notify(struct notifier_bloc switch (action) { case CPU_ONLINE: case CPU_UP_CANCELED: + case CPU_DEAD: + case CPU_DYING: + case CPU_DOWN_FAILED: if (try_acquire_console_sem() == 0) release_console_sem(); } Regards Santosh -- 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/