Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752575Ab2HCJoW (ORCPT ); Fri, 3 Aug 2012 05:44:22 -0400 Received: from e23smtp03.au.ibm.com ([202.81.31.145]:38057 "EHLO e23smtp03.au.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751636Ab2HCJoV (ORCPT ); Fri, 3 Aug 2012 05:44:21 -0400 From: Nikunj A Dadhania To: Vikram Pandita , gregkh@linuxfoundation.org, kay@vrfy.org Cc: linux-kernel@vger.kernel.org, Vikram Pandita , Mike Turquette , Vimarsh Zutshi Subject: Re: [PATCH v2] printk: add option to print cpu id In-Reply-To: <1343985378-22330-1-git-send-email-vikram.pandita@ti.com> References: <1343985378-22330-1-git-send-email-vikram.pandita@ti.com> User-Agent: Notmuch/0.10.2+70~gf0e0053 (http://notmuchmail.org) Emacs/24.0.95.1 (x86_64-unknown-linux-gnu) Date: Fri, 03 Aug 2012 15:13:16 +0530 Message-ID: <87wr1g5n0r.fsf@abhimanyu.in.ibm.com> MIME-Version: 1.0 Content-Type: text/plain x-cbid: 12080309-6102-0000-0000-000001FE00A1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3764 Lines: 108 On Fri, 3 Aug 2012 02:16:18 -0700, Vikram Pandita wrote: > From: Vikram Pandita > > Introduce config option to enable CPU id reporting for printk() calls. > > Example logs with this option enabled look like: > [1] [ 2.328613] usbcore: registered new interface driver libusual > [1] [ 2.335418] usbcore: registered new interface driver usbtest > [1] [ 2.342803] mousedev: PS/2 mouse device common for all mice > [0] [ 2.352600] twl_rtc twl_rtc: Power up reset detected. > [0] [ 2.359191] twl_rtc twl_rtc: Enabling TWL-RTC > [1] [ 2.367797] twl_rtc twl_rtc: rtc core: registered twl_rtc as rtc0 > [1] [ 2.375274] i2c /dev entries driver > [1] [ 2.382324] Driver for 1-wire Dallas network protocol. > > 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: Kay Sievers > Cc: Mike Turquette > Cc: Vimarsh Zutshi > --- > v1: initial version - had wrong cpuid logging mechanism > v2: fixed as per review comments from Kay Sievers > > kernel/printk.c | 51 +++++++++++++++++++++++++++++++++++++++++---------- > lib/Kconfig.debug | 13 +++++++++++++ > 2 files changed, 54 insertions(+), 10 deletions(-) > > diff --git a/kernel/printk.c b/kernel/printk.c > index 6a76ab9..64f4a1b 100644 > --- a/kernel/printk.c > +++ b/kernel/printk.c > @@ -208,6 +208,7 @@ struct log { > u8 facility; /* syslog facility */ > u8 flags:5; /* internal record flags */ > u8 level:3; /* syslog level */ > + u8 cpuid; /* cpu invoking the log */ > }; That would be sufficient for only 256 cpus. Is that what you intend? There are systems which will have much higher numbers than this limit. > /* > @@ -305,7 +306,8 @@ static u32 log_next(u32 idx) > static void log_store(int facility, int level, > enum log_flags flags, u64 ts_nsec, > const char *dict, u16 dict_len, > - const char *text, u16 text_len) > + const char *text, u16 text_len, > + const u8 cpuid) > { > struct log *msg; > u32 size, pad_len; > @@ -356,6 +358,7 @@ static void log_store(int facility, int level, > msg->ts_nsec = local_clock(); > memset(log_dict(msg) + dict_len, 0, pad_len); > msg->len = sizeof(struct log) + text_len + dict_len + pad_len; > + msg->cpuid = cpuid; > > /* insert message */ > log_next_idx += msg->len; > @@ -855,6 +858,25 @@ 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(u8 cpuid, char *buf) > +{ > + > + if (!printk_cpuid) > + return 0; > + > + if (!buf) > + return 4; > + Firstly, why this magic number? Secondly, if buf is NULL, why should you increment? > + return sprintf(buf, "[%1d] ", cpuid); > +} > + > static size_t print_prefix(const struct log *msg, bool syslog, char *buf) > { > size_t len = 0; Regards Nikunj -- 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/