From mboxrd@z Thu Jan 1 00:00:00 1970 From: Thomas Gleixner Subject: Re: [PATCH v3]PM/Sleep: Timer quiesce in freeze state Date: Mon, 26 Jan 2015 15:34:22 +0100 (CET) Message-ID: References: <54866625.8010406@linux.intel.com> <2137807.aqSxQQCuJ3@vostro.rjw.lan> <2076277.JWdUtd56Il@vostro.rjw.lan> Mime-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Return-path: In-Reply-To: <2076277.JWdUtd56Il@vostro.rjw.lan> Sender: linux-kernel-owner@vger.kernel.org To: "Rafael J. Wysocki" Cc: "Li, Aubrey" , Peter Zijlstra , "Brown, Len" , "alan@linux.intel.com" , LKML , Linux PM list List-Id: linux-pm@vger.kernel.org On Mon, 26 Jan 2015, Rafael J. Wysocki wrote: > On Monday, January 26, 2015 03:24:27 PM Thomas Gleixner wrote: > > On Mon, 26 Jan 2015, Rafael J. Wysocki wrote: > > > On Monday, January 26, 2015 10:40:24 AM Thomas Gleixner wrote: > > > > The only remaining issue might be a NMI calling into > > > > ktime_get_mono_fast_ns() before timekeeping is resumed. Its probably a > > > > non issue on x86/tsc, but it might be a problem on other platforms > > > > which turn off devices, clocks, It's not rocket science to prevent > > > > that. > > > > > > I don't see any users of ktime_get_mono_fast_ns() at all, unless some non-trivial > > > macros are involved. At least grepping for it only returns the definition, > > > declarations and the line in trace.c. > > > > You can trace in NMI and perf is going to use ktime_get_mono_fast_ns() > > eventually as well. > > So I'm not sure how to intercept that to be honest. Any hints? If we suspend timekeeping we can make the fast timekeeper point at a dummy readout function which returns the time at suspend, if the clock source does not resume automagically. As I said TSC should be a non issue, but other stuff might be. We could make it conditional on CLOCK_SOURCE_SUSPEND_NONSTOP perhaps. Thanks, tglx