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Date: Wed, 24 Nov 2021 15:34:49 -0800
From: Jakub Kicinski <kuba@...nel.org>
To: Stefan Dietrich <roots@....de>
Cc: Greg KH <greg@...ah.com>, netdev@...r.kernel.org,
stable@...r.kernel.org, regressions@...ts.linux.dev,
Vinicius Costa Gomes <vinicius.gomes@...el.com>,
Dvora Fuxbrumer <dvorax.fuxbrumer@...ux.intel.com>,
Tony Nguyen <anthony.l.nguyen@...el.com>,
intel-wired-lan@...ts.osuosl.org
Subject: Re: [REGRESSION] Kernel 5.15 reboots / freezes upon ifup/ifdown
On Wed, 24 Nov 2021 18:20:40 +0100 Stefan Dietrich wrote:
> Hi all,
>
> six exciting hours and a lot of learning later, here it is.
> Symptomatically, the critical commit appears for me between 5.14.21-
> 051421-generic and 5.15.0-051500rc2-generic - I did not find an amd64
> build for rc1.
>
> Please see the git-bisect output below and let me know how I may
> further assist in debugging!
Well, let's CC those involved, shall we? :)
Thanks for working thru the bisection!
> a90ec84837325df4b9a6798c2cc0df202b5680bd is the first bad commit
> commit a90ec84837325df4b9a6798c2cc0df202b5680bd
> Author: Vinicius Costa Gomes <vinicius.gomes@...el.com>
> Date: Mon Jul 26 20:36:57 2021 -0700
>
> igc: Add support for PTP getcrosststamp()
>
> i225 supports PCIe Precision Time Measurement (PTM), allowing us to
> support the PTP_SYS_OFFSET_PRECISE ioctl() in the driver via the
> getcrosststamp() function.
>
> The easiest way to expose the PTM registers would be to configure
> the PTM
> dialogs to run periodically, but the PTP_SYS_OFFSET_PRECISE ioctl()
> semantics are more aligned to using a kind of "one-shot" way of
> retrieving
> the PTM timestamps. But this causes a bit more code to be written:
> the
> trigger registers for the PTM dialogs are not cleared
> automatically.
>
> i225 can be configured to send "fake" packets with the PTM
> information, adding support for handling these types of packets is
> left for the future.
>
> PTM improves the accuracy of time synchronization, for example,
> using
> phc2sys, while a simple application is sending packets as fast as
> possible. First, without .getcrosststamp():
>
> phc2sys[191.382]: enp4s0 sys offset -959 s2 freq -454
> delay 4492
> phc2sys[191.482]: enp4s0 sys offset 798 s2 freq +1015
> delay 4069
> phc2sys[191.583]: enp4s0 sys offset 962 s2 freq +1418
> delay 3849
> phc2sys[191.683]: enp4s0 sys offset 924 s2 freq +1669
> delay 3753
> phc2sys[191.783]: enp4s0 sys offset 664 s2 freq +1686
> delay 3349
> phc2sys[191.883]: enp4s0 sys offset 218 s2 freq +1439
> delay 2585
> phc2sys[191.983]: enp4s0 sys offset 761 s2 freq +2048
> delay 3750
> phc2sys[192.083]: enp4s0 sys offset 756 s2 freq +2271
> delay 4061
> phc2sys[192.183]: enp4s0 sys offset 809 s2 freq +2551
> delay 4384
> phc2sys[192.283]: enp4s0 sys offset -108 s2 freq +1877
> delay 2480
> phc2sys[192.383]: enp4s0 sys offset -1145 s2 freq +807
> delay 4438
> phc2sys[192.484]: enp4s0 sys offset 571 s2 freq +2180
> delay 3849
> phc2sys[192.584]: enp4s0 sys offset 241 s2 freq +2021
> delay 3389
> phc2sys[192.684]: enp4s0 sys offset 405 s2 freq +2257
> delay 3829
> phc2sys[192.784]: enp4s0 sys offset 17 s2 freq +1991
> delay 3273
> phc2sys[192.884]: enp4s0 sys offset 152 s2 freq +2131
> delay 3948
> phc2sys[192.984]: enp4s0 sys offset -187 s2 freq +1837
> delay 3162
> phc2sys[193.084]: enp4s0 sys offset -1595 s2 freq +373
> delay 4557
> phc2sys[193.184]: enp4s0 sys offset 107 s2 freq +1597
> delay 3740
> phc2sys[193.284]: enp4s0 sys offset 199 s2 freq +1721
> delay 4010
> phc2sys[193.385]: enp4s0 sys offset -169 s2 freq +1413
> delay 3701
> phc2sys[193.485]: enp4s0 sys offset -47 s2 freq +1484
> delay 3581
> phc2sys[193.585]: enp4s0 sys offset -65 s2 freq +1452
> delay 3778
> phc2sys[193.685]: enp4s0 sys offset 95 s2 freq +1592
> delay 3888
> phc2sys[193.785]: enp4s0 sys offset 206 s2 freq +1732
> delay 4445
> phc2sys[193.885]: enp4s0 sys offset -652 s2 freq +936
> delay 2521
> phc2sys[193.985]: enp4s0 sys offset -203 s2 freq +1189
> delay 3391
> phc2sys[194.085]: enp4s0 sys offset -376 s2 freq +955
> delay 2951
> phc2sys[194.185]: enp4s0 sys offset -134 s2 freq +1084
> delay 3330
> phc2sys[194.285]: enp4s0 sys offset -22 s2 freq +1156
> delay 3479
> phc2sys[194.386]: enp4s0 sys offset 32 s2 freq +1204
> delay 3602
> phc2sys[194.486]: enp4s0 sys offset 122 s2 freq +1303
> delay 3731
>
> Statistics for this run (total of 2179 lines), in nanoseconds:
> average: -1.12
> stdev: 634.80
> max: 1551
> min: -2215
>
> With .getcrosststamp() via PCIe PTM:
>
> phc2sys[367.859]: enp4s0 sys offset 6 s2 freq +1727
> delay 0
> phc2sys[367.959]: enp4s0 sys offset -2 s2 freq +1721
> delay 0
> phc2sys[368.059]: enp4s0 sys offset 5 s2 freq +1727
> delay 0
> phc2sys[368.160]: enp4s0 sys offset -1 s2 freq +1723
> delay 0
> phc2sys[368.260]: enp4s0 sys offset -4 s2 freq +1719
> delay 0
> phc2sys[368.360]: enp4s0 sys offset -5 s2 freq +1717
> delay 0
> phc2sys[368.460]: enp4s0 sys offset 1 s2 freq +1722
> delay 0
> phc2sys[368.560]: enp4s0 sys offset -3 s2 freq +1718
> delay 0
> phc2sys[368.660]: enp4s0 sys offset 5 s2 freq +1725
> delay 0
> phc2sys[368.760]: enp4s0 sys offset -1 s2 freq +1721
> delay 0
> phc2sys[368.860]: enp4s0 sys offset 0 s2 freq +1721
> delay 0
> phc2sys[368.960]: enp4s0 sys offset 0 s2 freq +1721
> delay 0
> phc2sys[369.061]: enp4s0 sys offset 4 s2 freq +1725
> delay 0
> phc2sys[369.161]: enp4s0 sys offset 1 s2 freq +1724
> delay 0
> phc2sys[369.261]: enp4s0 sys offset 4 s2 freq +1727
> delay 0
> phc2sys[369.361]: enp4s0 sys offset 8 s2 freq +1732
> delay 0
> phc2sys[369.461]: enp4s0 sys offset 7 s2 freq +1733
> delay 0
> phc2sys[369.561]: enp4s0 sys offset 4 s2 freq +1733
> delay 0
> phc2sys[369.661]: enp4s0 sys offset 1 s2 freq +1731
> delay 0
> phc2sys[369.761]: enp4s0 sys offset 1 s2 freq +1731
> delay 0
> phc2sys[369.861]: enp4s0 sys offset -5 s2 freq +1725
> delay 0
> phc2sys[369.961]: enp4s0 sys offset -4 s2 freq +1725
> delay 0
> phc2sys[370.062]: enp4s0 sys offset 2 s2 freq +1730
> delay 0
> phc2sys[370.162]: enp4s0 sys offset -7 s2 freq +1721
> delay 0
> phc2sys[370.262]: enp4s0 sys offset -3 s2 freq +1723
> delay 0
> phc2sys[370.362]: enp4s0 sys offset 1 s2 freq +1726
> delay 0
> phc2sys[370.462]: enp4s0 sys offset -3 s2 freq +1723
> delay 0
> phc2sys[370.562]: enp4s0 sys offset -1 s2 freq +1724
> delay 0
> phc2sys[370.662]: enp4s0 sys offset -4 s2 freq +1720
> delay 0
> phc2sys[370.762]: enp4s0 sys offset -7 s2 freq +1716
> delay 0
> phc2sys[370.862]: enp4s0 sys offset -2 s2 freq +1719
> delay 0
>
> Statistics for this run (total of 2179 lines), in nanoseconds:
> average: 0.14
> stdev: 5.03
> max: 48
> min: -27
>
> For reference, the statistics for runs without PCIe congestion show
> that the improvements from enabling PTM are less dramatic. For two
> runs of 16466 entries:
> without PTM: avg -0.04 stdev 10.57 max 39 min -42
> with PTM: avg 0.01 stdev 4.20 max 19 min -16
>
> One possible explanation is that when PTM is not enabled, and
> there's a lot
> of traffic in the PCIe fabric, some register reads will take more
> time
> than the others because of congestion on the PCIe fabric.
>
> When PTM is enabled, even if the PTM dialogs take more time to
> complete under heavy traffic, the time measurements do not depend
> on
> the time to read the registers.
>
> This was implemented following the i225 EAS version 0.993.
>
> Signed-off-by: Vinicius Costa Gomes <vinicius.gomes@...el.com>
> Tested-by: Dvora Fuxbrumer <dvorax.fuxbrumer@...ux.intel.com>
> Signed-off-by: Tony Nguyen <anthony.l.nguyen@...el.com>
>
> drivers/net/ethernet/intel/igc/igc.h | 1 +
> drivers/net/ethernet/intel/igc/igc_defines.h | 31 +++++
> drivers/net/ethernet/intel/igc/igc_ptp.c | 179
> +++++++++++++++++++++++++++
> drivers/net/ethernet/intel/igc/igc_regs.h | 23 ++++
> 4 files changed, 234 insertions(+)
>
>
> On Wed, 2021-11-24 at 08:33 +0100, Greg KH wrote:
> > On Wed, Nov 24, 2021 at 08:28:39AM +0100, Stefan Dietrich wrote:
> > > Summary: When attempting to rise or shut down a NIC manually or via
> > > network-manager under 5.15, the machine reboots or freezes.
> > >
> > > Occurs with: 5.15.4-051504-generic and earlier 5.15 mainline (
> > > https://kernel.ubuntu.com/~kernel-ppa/mainline/v5.15.4/) as well as
> > > liquorix flavours.
> > > Does not occur with: 5.14 and 5.13 (both with various flavours)
> >
> > Can you use 'git bisect' between 5.14 and 5.15 to find the problem
> > commit?
> >
> > thanks,
> >
> > greg k-h
>
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