Bug#827323: linux: Regression v4.5 -> v4.6: system freeze after suspend/resume due to iAMT watchdog
Hi
It may be that fdd9b8655933 uncovered the bug in iTCO_wdt because it actually removes iAMT watchdog and new
implementation does not creates one for not provisioned ME.
So before that patch there was two watchdog devices and systemd maybe worked with iAMT one.
After that patch only one watchdog exists in the system - iTCO and system works with it.
Thanks
--
Sasha
-----Original Message-----
From: Sebastian Reichel [mailto:sre@debian.org]
Sent: Wednesday, June 15, 2016 14:30
To: Usyskin, Alexander <alexander.usyskin@intel.com>
Cc: 827323@bugs.debian.org
Subject: Re: Bug#827323: linux: Regression v4.5 -> v4.6: system freeze after suspend/resume due to iAMT watchdog
Hi,
On Wed, Jun 15, 2016 at 08:00:30AM +0000, Usyskin, Alexander wrote:
> I assume that "This happened with 4.6, but not with v4.5.", yes?
Yes, sorry.
> Do you have vPro system?
Yes, my CPU is i7-5600U.
> Have you provisioned your ME device?
No, I don't think so.
> If not, the iAMT watchdog should not be exposed to user-space and
> should not affect systemd. Do you have /dev/watchdog* with identity
> "iamt_wdt" at you system?
# ls /sys/class/watchdog
watchdog0
# wd_identify
iTCO_wdt
That's also, what was used by systemd:
Jun 15 01:24:49 earth kernel: iTCO_wdt: Intel TCO WatchDog Timer Driver v1.11 Jun 15 01:24:49 earth kernel: iTCO_wdt: Found a Wildcat Point_LP TCO device (Version=2, TCOBASE=0x1860) Jun 15 01:24:49 earth kernel: iTCO_wdt: initialized. heartbeat=30 sec (nowayout=0) Jun 15 01:24:49 earth systemd[1]: Hardware watchdog 'iTCO_wdt', version 0 Jun 15 01:24:49 earth systemd[1]: Set hardware watchdog to 30s.
I have checked with wd_keepalive and I have a few more observations:
* The freeze did not appear when wd_keepalive is used instead of systemd
* The freeze appears, if I kill wd_keepalive, so the freeze itself seems
to be a bug in the iTCO_wdt driver/hardware.
So looks like fdd9b8655933 somehow results in systemd being too slow to ping the watchdog in time.
-- Sebastian
> -----Original Message-----
> From: Sebastian Reichel [mailto:sre@debian.org]
> Sent: Wednesday, June 15, 2016 02:44
> To: Debian Bug Tracking System <submit@bugs.debian.org>
> Subject: Bug#827323: linux: Regression v4.5 -> v4.6: system freeze
> after suspend/resume due to iAMT watchdog
>
> Source: linux
> Version: 4.5.5-1
> Severity: normal
>
> Hi,
>
> My Lenovo Thinkpad X250 freezes a couple of seconds after resuming
> from suspend. This happened with 4.5, but not with v4.6. I bisected
> the problem using mainline kernel with Debian config to the following
> commit:
>
> sre@earth ~/src/linux (git)-[fdd9b86...|bisect] % git bisect bad
> fdd9b8655933c3eb3154fe1ed351c17b654258bd is the first bad commit
> commit fdd9b8655933c3eb3154fe1ed351c17b654258bd
> Author: Alexander Usyskin <alexander.usyskin@intel.com>
> Date: Fri Jan 8 00:49:21 2016 +0200
>
> mei: wd: drop the watchdog code from the core mei driver
>
> Instead of integrating the iAMT watchdog in the mei core driver
> we will create a watchdog device on the mei client bus and
> create a driver for it.
>
> This patch removes the watchdog code from the mei core driver.
>
> Signed-off-by: Alexander Usyskin <alexander.usyskin@intel.com>
> Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
>
> My system was configured to use the watchdog via "RuntimeWatchdogSec=30"
> in "/etc/systemd/system.conf". After disabling the feature no system
> freeze happens after suspend/resume cycle.
>
> -- Sebastian
>
> -- System Information:
> Debian Release: stretch/sid
> APT prefers testing
> APT policy: (1000, 'testing'), (500, 'unstable'), (200,
> 'experimental')
> Architecture: amd64 (x86_64)
> Foreign Architectures: i386, armhf
>
> Kernel: Linux 4.6.0-1-amd64 (SMP w/4 CPU cores)
> Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8)
> Shell: /bin/sh linked to /bin/dash
> Init: systemd (via /run/systemd/system)
> ---------------------------------------------------------------------
> Intel Israel (74) Limited
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