Hello Greg, Thank you for your feedback. > Subject: Re: [PATCH] time: Fix CLOCK_MONOTONIC_RAW sub-nanosecond accounting > > On Mon, May 21, 2018 at 06:57:26PM +0100, Fabrizio Castro wrote: > > From: John Stultz <john.stultz@xxxxxxxxxx> > > > > commit 3d88d56c5873f6eebe23e05c3da701960146b801 upstream. > > > > Due to how the MONOTONIC_RAW accumulation logic was handled, > > there is the potential for a 1ns discontinuity when we do > > accumulations. This small discontinuity has for the most part > > gone un-noticed, but since ARM64 enabled CLOCK_MONOTONIC_RAW > > in their vDSO clock_gettime implementation, we've seen failures > > with the inconsistency-check test in kselftest. > > > > This patch addresses the issue by using the same sub-ns > > accumulation handling that CLOCK_MONOTONIC uses, which avoids > > the issue for in-kernel users. > > > > Since the ARM64 vDSO implementation has its own clock_gettime > > calculation logic, this patch reduces the frequency of errors, > > but failures are still seen. The ARM64 vDSO will need to be > > updated to include the sub-nanosecond xtime_nsec values in its > > calculation for this issue to be completely fixed. > > > > Signed-off-by: John Stultz <john.stultz@xxxxxxxxxx> > > Tested-by: Daniel Mentz <danielmentz@xxxxxxxxxx> > > Cc: Prarit Bhargava <prarit@xxxxxxxxxx> > > Cc: Kevin Brodsky <kevin.brodsky@xxxxxxx> > > Cc: Richard Cochran <richardcochran@xxxxxxxxx> > > Cc: Stephen Boyd <stephen.boyd@xxxxxxxxxx> > > Cc: Will Deacon <will.deacon@xxxxxxx> > > Cc: "stable #4 . 8+" <stable@xxxxxxxxxxxxxxx> > > Cc: Miroslav Lichvar <mlichvar@xxxxxxxxxx> > > Link: http://lkml.kernel.org/r/1496965462-20003-3-git-send-email-john.stultz@xxxxxxxxxx > > Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx> > > [fabrizio: cherry-pick to 4.4. Kept cycle_t type for function > > logarithmic_accumulation local variable "interval". Dropped > > casting of "interval" variable] > > Signed-off-by: Fabrizio Castro <fabrizio.castro@xxxxxxxxxxxxxx> > > Signed-off-by: Biju Das <biju.das@xxxxxxxxxxxxxx> > > --- > > Hello Greg, > > > > we noticed tools/testing/selftests/timers/clocksource-switch.c > > was failing for us, this patch fixes the cause of the failure. > > Are you happy to take this patch? > > For what kernel tree(s)? 4.4.y > > And why did you not cc: the developers and maintainer of this subsystem? Sorry, I wasn't sure about bothering the other developers with this. I'll repost with all the relevant people in cc. Thanks, Fab > > thanks, > > greg k-h Renesas Electronics Europe Ltd, Dukes Meadow, Millboard Road, Bourne End, Buckinghamshire, SL8 5FH, UK. Registered in England & Wales under Registered No. 04586709.
