From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752773Ab2LXDyo (ORCPT ); Sun, 23 Dec 2012 22:54:44 -0500 Received: from mga11.intel.com ([192.55.52.93]:59826 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752513Ab2LXDyl (ORCPT ); Sun, 23 Dec 2012 22:54:41 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.84,343,1355126400"; d="scan'208";a="269272413" Subject: Re: [PATCH] output the cpu number when printking. From: "he, bo" To: Randy Dunlap Cc: akpm@linux-foundation.org, mingo@elte.hu, a.p.zijlstra@chello.nl, linux-kernel@vger.kernel.org, yanmin_zhang@linux.intel.com In-Reply-To: <50D7CDED.4060308@infradead.org> References: <1356316276.2385.7.camel@hebo> <50D7CDED.4060308@infradead.org> Content-Type: text/plain; charset="UTF-8" Date: Mon, 24 Dec 2012 11:54:15 +0800 Message-ID: <1356321255.2385.8.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 Thanks randy's comments, I will modifiy it. On Sun, 2012-12-23 at 19:37 -0800, Randy Dunlap wrote: > On 12/23/12 18:31, he, bo wrote: > > 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. > > Above line needs to be indented more (beginning under "Format:"). > > > + > > 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) > > > >