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Date: Thu, 4 Feb 2016 18:25:29 +0100 (CET) From: Thomas Gleixner <tglx@...utronix.de> To: Petr Mladek <pmladek@...e.com> cc: Prarit Bhargava <prarit@...hat.com>, linux-kernel@...r.kernel.org, John Stultz <john.stultz@...aro.org>, Xunlei Pang <pang.xunlei@...aro.org>, Baolin Wang <baolin.wang@...aro.org>, Andrew Morton <akpm@...ux-foundation.org>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Tejun Heo <tj@...nel.org>, Peter Hurley <peter@...leysoftware.com>, Vasily Averin <vvs@...tuozzo.com>, Joe Perches <joe@...ches.com> Subject: Re: [PATCH] printk, allow different timestamps for printk.time [v2] On Thu, 4 Feb 2016, Petr Mladek wrote: > On Thu 2016-01-28 07:43:49, Prarit Bhargava wrote: > > +static u64 printk_get_ts(void) > > +{ > > + u64 mono, offset_real; > > + > > + if (printk_time == 0) > > + return 0; > > + > > + if (printk_time == 1) > > + return local_clock(); > > + > > + mono = ktime_get_log_ts(&offset_real); > > + > > + if (printk_time == 2) > > + return mono; > > + > > + return mono + offset_real; > > At least dmesg is not capable to read the absolute size of the > real time. It expects offset against the start of the timekeeping > stuff or so. I get this: > > $> dmesg | tail -n 5 > [ 7.128924] IPv6: ADDRCONF(NETDEV_CHANGE): eth0: link becomes ready > [ 0.000000] printk: timestamp set to 0. > [ 179.983704] printk: timestamp set to 1. > [ 181.895655] printk: timestamp set to 2. > [1454602412.026424] printk: timestamp set to 3. > > $dmesg -T -S | tail -n 5 > [Thu Feb 4 17:10:34 2016] IPv6: ADDRCONF(NETDEV_CHANGE): eth0: link becomes ready > [Thu Feb 4 17:10:27 2016] printk: timestamp set to 0. > [Thu Feb 4 17:13:26 2016] printk: timestamp set to 1. > [Thu Feb 4 17:13:28 2016] printk: timestamp set to 2. > [Fri Mar 10 09:23:59 2062] printk: timestamp set to 3. > > Please, note that the last entry points to the year 2062. That's a problem of dmesg -T -S. It doesn't know that the timestamp (3) is actually CLOCKTIME_REAL already: -> 1454602412 / (3600 * 24 * 365) = 46.1251 -> 1970 + 46 = 2016 Thanks, tglx
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