Re: [Linuxptp-users] phc offset explodes after a while

[Koehrer M. (ETAS/ESW5) <mat...@et...>]

Hi Richard,

thanks for the response and the hint.
> > Kernel 3.2.48-rt69 (RT_PREEMPT patch).
> > I use the Intel Gigabit CT Desktop adapter (82574L).
> > For this is use the latest e1000e driver (Version 2.5.4) and build it outside
> the kernel to have the PTP support.
> 
> ...
> 
> > This works really fine for a while. However after a while the value of phc
> explodes dramatically.
> > The value will be -35192325800 which looks like a kind of value overrun!
> > In hex this is 0xFFFFFFF7CE5FB958.
> 
> This sounds like a RT_PREEMPT issue. That patch makes spinlocks
> preemptable, and the 82574 does need real locking, IIRC.
> 
> Can you reproduce the problem with RT_PREEMPT disabled?
I have used the very same kernel 3.2.48 without the RT_PREEMPT patch using
the same configuration.
Also here, I got the same issue after a while (it took more than 30 minutes).
I added some print-outs to the file clock.c in function clock_synchronize().
Directly after the c->master_offset = tmv_sub(....) call I printed out the values that are used in the computation.
Below is the related snippet from the logfile.
There is a jump in the value of "origin" that seems to  cause the issue.

Any ideas?

Thanks a lot!

Best regards

Mathias

------------ BEGIN SNIPPET ----
Jan 30 14:40:46 pca ptp4l: [2060.928] ingress:1391089281141037037  origin:1391089281141036324 path_delay:738 c1:0 c2:0
Jan 30 14:40:46 pca ptp4l: [2060.928] master offset        -25 s2 freq   -6231 path delay       738
Jan 30 14:40:46 pca phc2sys: [2061.632] phc offset      2066 s2 freq  +32240 delay   6073
Jan 30 14:40:47 pca ptp4l: [2061.928] ingress:1391089282141051035  origin:1391089282141050284 path_delay:734 c1:0 c2:0
Jan 30 14:40:47 pca ptp4l: [2061.928] master offset         17 s2 freq   -6197 path delay       734
Jan 30 14:40:47 pca phc2sys: [2062.632] phc offset      3961 s2 freq  +34755 delay   6393
Jan 30 14:40:48 pca ptp4l: [2062.928] ingress:1391089283141068939  origin:1391089283141068244 path_delay:734 c1:0 c2:0
Jan 30 14:40:48 pca ptp4l: [2062.928] master offset        -39 s2 freq   -6248 path delay       734
Jan 30 14:40:48 pca phc2sys: [2063.632] phc offset     -7230 s2 freq  +24752 delay   6178
Jan 30 14:40:49 pca ptp4l: [2063.927] ingress:1391089284141082537  origin:1391089284141081804 path_delay:732 c1:0 c2:0
Jan 30 14:40:49 pca ptp4l: [2063.927] master offset          1 s2 freq   -6220 path delay       732
Jan 30 14:40:49 pca phc2sys: [2064.632] phc offset      -952 s2 freq  +28861 delay   6655
############# The following line shows the jump in origin which causes the master offset to be really large!
Jan 30 14:40:50 pca ptp4l: [2064.928] ingress:1391089285141017574  origin:1391159653885194468 path_delay:734 c1:0 c2:0
Jan 30 14:40:50 pca ptp4l: [2064.928] master offset -70368744177628 s2 freq -599999999 path delay       734
Jan 30 14:40:50 pca phc2sys: [2065.633] phc offset -422734042 s2 freq -500000 delay   6740
Jan 30 14:40:51 pca ptp4l: [2065.928] ingress:1391089286738705674  origin:1391159654884640068 path_delay:3007 c1:0 c2:0
Jan 30 14:40:51 pca ptp4l: [2065.928] master offset -70368145937401 s2 freq -599999999 path delay      3007
Jan 30 14:40:51 pca phc2sys: [2066.633] phc offset -1021983284 s2 freq -500000 delay   6721
Jan 30 14:40:52 pca ptp4l: [2066.926] ingress:1391089288337875110  origin:1391159655884127148 path_delay:5266 c1:0 c2:0
Jan 30 14:40:52 pca ptp4l: [2066.926] master offset -70367546257304 s2 freq -599999999 path delay      5266
Jan 30 14:40:52 pca phc2sys: [2067.633] phc offset -1621224622 s2 freq -500000 delay   6737
Jan 30 14:40:53 pca ptp4l: [2067.928] ingress:1391089289937036930  origin:1391159656883609508 path_delay:7518 c1:0 c2:0
Jan 30 14:40:53 pca ptp4l: [2067.928] master offset -70366946580096 s2 freq -599999999 path delay      7518
------ END SNIPPET ------