From mboxrd@z Thu Jan 1 00:00:00 1970 From: Thomas Gleixner Subject: Re: [PATCH v2 1/4] time: rtc-lib: Add rtc_show_time(const char *prefix_msg) Date: Tue, 18 Jul 2017 23:52:16 +0200 (CEST) Message-ID: References: <20170718211930.123077-1-salyzyn@android.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Return-path: In-Reply-To: <20170718211930.123077-1-salyzyn@android.com> Sender: linux-kernel-owner@vger.kernel.org To: Mark Salyzyn Cc: linux-kernel@vger.kernel.org, rjw@rjwysocki.net, len.brown@intel.com, pavel@ucw.cz, linux-pm@vger.kernel.org, a.zummo@towertech.it, alexandre.belloni@free-electrons.com, linux-rtc@vger.kernel.org, andy.shevchenko@gmail.com, Mark Salyzyn , "Paul E. McKenney" , Thierry Strudel , John Stultz , Richard Cochran , Nicolas Pitre , Kees Cook List-Id: linux-pm@vger.kernel.org On Tue, 18 Jul 2017, Mark Salyzyn wrote: > Go directly to the rtc for persistent wall clock time and print. > Useful if REALTIME is required to be logged in a low level power > management function or when clock activities are suspended. An > aid to permit user space alignment of kernel activities. That's a horrible idea, really. And there is no point at all. > +void rtc_show_time(const char *prefix_msg) > +{ > + struct timespec ts; > + struct rtc_time tm; > + > + getnstimeofday(&ts); It calls getnstimeofday(), which is wrong to begin with as we switch everything in kernel to the 64bit variants. > + rtc_time64_to_tm(ts.tv_sec, &tm); This is even more wrong as rtc_time64_to_tm is for 64 bit wide second values.... > + pr_info("%s %d-%02d-%02d %02d:%02d:%02d.%09lu UTC\n", > + prefix_msg ? prefix_msg : "Time:", > + tm.tm_year + 1900, tm.tm_mon + 1, tm.tm_mday, > + tm.tm_hour, tm.tm_min, tm.tm_sec, ts.tv_nsec); Why on earth do you need to print that information in RTC format? What's wrong with just doing: pr_info("My so important log message %lld\n", ktime_get_real_seconds()); and then decoding the seconds in post processing? That's completely sufficient as you intend that for logging. Correlation with user space CLOCK_REALTIME is even simpler as this is the same as reading it from user space. If your main intention is logging/debugging, then you can just use tracepoints. The tracer allows correlation to user space tracing already. So unless you can come up with a reasonable explanation why all this voodoo is required, this is going nowhere. Thanks, tglx