Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752616Ab2HBTqQ (ORCPT ); Thu, 2 Aug 2012 15:46:16 -0400 Received: from devils.ext.ti.com ([198.47.26.153]:44551 "EHLO devils.ext.ti.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751268Ab2HBTqO (ORCPT ); Thu, 2 Aug 2012 15:46:14 -0400 From: Vikram Pandita To: , CC: , Vikram Pandita , Mike Turquette , Vimarsh Zutshi Subject: [PATCH] printk: add option to print cpu id Date: Thu, 2 Aug 2012 12:46:04 -0700 Message-ID: <1343936764-6461-1-git-send-email-vikram.pandita@ti.com> X-Mailer: git-send-email 1.7.9.5 MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2718 Lines: 91 From: Vikram Pandita Introduce config option to enable CPU id reporting for printk() calls. Its sometimes very useful to have printk also print the CPU Identifier that executed the call. This has helped to debug various SMP issues on shipping products. Known limitation is, if the system gets preempted between function call and actual printk, the reported cpu-id might not be accurate. But most of the times its seen to give a good feel of how the N cpu's in the system are getting loaded. Signed-off-by: Vikram Pandita Cc: Mike Turquette Cc: Vimarsh Zutshi --- kernel/printk.c | 20 ++++++++++++++++++++ lib/Kconfig.debug | 13 +++++++++++++ 2 files changed, 33 insertions(+) diff --git a/kernel/printk.c b/kernel/printk.c index 6a76ab9..50feb82 100644 --- a/kernel/printk.c +++ b/kernel/printk.c @@ -855,6 +855,25 @@ static size_t print_time(u64 ts, char *buf) (unsigned long)ts, rem_nsec / 1000); } +#if defined(CONFIG_PRINTK_CPUID) +static bool printk_cpuid = 1; +#else +static bool printk_cpuid; +#endif +module_param_named(cpuid, printk_cpuid, bool, S_IRUGO | S_IWUSR); + +static size_t print_cpuid(char *buf) +{ + + if (!printk_cpuid) + return 0; + + if (!buf) + return 4; + + return sprintf(buf, "[%1d] ", smp_processor_id()); +} + static size_t print_prefix(const struct log *msg, bool syslog, char *buf) { size_t len = 0; @@ -874,6 +893,7 @@ static size_t print_prefix(const struct log *msg, bool syslog, char *buf) } } + len += print_cpuid(buf ? buf + len : NULL); len += print_time(msg->ts_nsec, buf ? buf + len : NULL); return len; } diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug index 2403a63..139b2b1 100644 --- a/lib/Kconfig.debug +++ b/lib/Kconfig.debug @@ -14,6 +14,19 @@ config PRINTK_TIME The behavior is also controlled by the kernel command line parameter printk.time=1. See Documentation/kernel-parameters.txt +config PRINTK_CPUID + bool "Show cpu id information on printks" + depends on PRINTK + help + Selecting this option causes cpu identifier to be added to the + output of the syslog() system call and at the console. + + This flag just specifies if the cpu-id should + be included. + + The behavior is also controlled by the kernel command line + parameter printk.cpuid=1. + config DEFAULT_MESSAGE_LOGLEVEL int "Default message log level (1-7)" range 1 7 -- 1.7.9.5 -- 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/