From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752757Ab2LXDgA (ORCPT ); Sun, 23 Dec 2012 22:36:00 -0500 Received: from casper.infradead.org ([85.118.1.10]:48910 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752302Ab2LXDf6 (ORCPT ); Sun, 23 Dec 2012 22:35:58 -0500 Message-ID: <50D7CDED.4060308@infradead.org> Date: Sun, 23 Dec 2012 19:37:17 -0800 From: Randy Dunlap User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/17.0 Thunderbird/17.0 MIME-Version: 1.0 To: "he, bo" CC: akpm@linux-foundation.org, mingo@elte.hu, a.p.zijlstra@chello.nl, linux-kernel@vger.kernel.org, yanmin_zhang@linux.intel.com Subject: Re: [PATCH] output the cpu number when printking. References: <1356316276.2385.7.camel@hebo> In-Reply-To: <1356316276.2385.7.camel@hebo> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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) > -- ~Randy