From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752789Ab2LXCbo (ORCPT ); Sun, 23 Dec 2012 21:31:44 -0500 Received: from mga14.intel.com ([143.182.124.37]:37936 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752388Ab2LXCbl (ORCPT ); Sun, 23 Dec 2012 21:31:41 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.84,343,1355126400"; d="scan'208";a="236019508" Subject: [PATCH] output the cpu number when printking. From: "he, bo" To: akpm@linux-foundation.org, mingo@elte.hu, a.p.zijlstra@chello.nl, linux-kernel@vger.kernel.org Cc: yanmin_zhang@linux.intel.com Content-Type: text/plain; charset="UTF-8" Date: Mon, 24 Dec 2012 10:31:16 +0800 Message-ID: <1356316276.2385.7.camel@hebo> Mime-Version: 1.0 X-Mailer: Evolution 2.30.3 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: "he, bo" We often hit kernel panic issues on SMP machines because processes race on multiple cpu. By adding a new parameter printk.cpu, kernel prints cpu number at printk information line. It’s useful to debug what cpus are racing. Signed-off-by: he, bo --- Documentation/kernel-parameters.txt | 4 ++++ kernel/printk.c | 18 ++++++++++++++++-- 2 files changed, 20 insertions(+), 2 deletions(-) diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt index ddd84d6..ccd5266 100644 --- a/Documentation/kernel-parameters.txt +++ b/Documentation/kernel-parameters.txt @@ -2378,6 +2378,10 @@ bytes respectively. Such letter suffixes can also be entirely omitted. printk.time= Show timing data prefixed to each printk message line Format: (1/Y/y=enable, 0/N/n=disable) + printk.cpu= Show cpu data prefixed to each printk message line + Format: (1/Y/y=enable, 0/N/n=disable) + printk.cpu takes effect only when printk.time=y. + processor.max_cstate= [HW,ACPI] Limit processor to maximum C-state max_cstate=9 overrides any DMI blacklist limit. diff --git a/kernel/printk.c b/kernel/printk.c index 19c0d7b..873a226 100644 --- a/kernel/printk.c +++ b/kernel/printk.c @@ -863,9 +863,14 @@ static bool printk_time; #endif module_param_named(time, printk_time, bool, S_IRUGO | S_IWUSR); +static bool printk_cpu = 1; +module_param_named(cpu, printk_cpu, bool, S_IRUGO | S_IWUSR); + static size_t print_time(u64 ts, char *buf) { unsigned long rem_nsec; + size_t len = 0; + int this_cpu; if (!printk_time) return 0; @@ -874,8 +879,17 @@ static size_t print_time(u64 ts, char *buf) return 15; rem_nsec = do_div(ts, 1000000000); - return sprintf(buf, "[%5lu.%06lu] ", - (unsigned long)ts, rem_nsec / 1000); + + if (printk_cpu) { + this_cpu = raw_smp_processor_id(); + len = sprintf(buf, "[%5lu.%06lu,%u] ", + (unsigned long)ts, rem_nsec / 1000, this_cpu); + } else { + len = sprintf(buf, "[%5lu.%06lu] ", + (unsigned long)ts, rem_nsec / 1000); + } + + return len; } static size_t print_prefix(const struct log *msg, bool syslog, char *buf) -- 1.7.6