Re: rcu_sched_state detected stall on CPU 0, 3.0-rc2

Let's CC netdev and linux-pm since this is obviously a suspend issue,
and may have something to do with ethtool.

On Sun, Jun 12, 2011 at 04:11:43PM -0700, Andy Isaacson wrote:

On Sun, Jun 12, 2011 at 12:58:56PM -0700, Andy Isaacson wrote:

quoted

My Thinkpad x201s threw some errors (?) a few minutes after resuming
from suspend-to-ram this morning.

[56415.672140] INFO: rcu_sched_state detected stall on CPU 0 (t=15000 jiffies)

Nothing jumps out of the backtraces at me.  Full dmesg and config
attached.  This was my first StR since upgrading from 2.6.39, let's see
if it fails again when I suspend after sending this email. :)

I haven't had a fully successful StR cycle yet (in 5 tries), although I
can't pin them all on RCU.  On try 2 it hung completely about 10 seconds
after I unlocked the screensaver, on try 3 it came back to a black
console, and on try 4 it didn't suspend at all (blinking moon LED but
battery LED and CPU fan still on).

Of course now that I'm trying to debug, I am seeing many successful
suspend-resume cycles.  I don't see any signs of difference between the
cases that hung and the cases that are now succeeding.

CCing netdev, because I suspend by running pm-suspend, and in at least
one failure, an ethtool running under pm-suspend seemed to be the
problem:

root 11558 pts/8    S+ \_ /bin/sh /usr/lib/pm-utils/sleep.d/00powers
root 11559 pts/8    S+     \_ /bin/sh /usr/sbin/pm-powersave
root 11576 pts/8    S+         \_ /bin/sh /usr/lib/pm-utils/power.d/
root 11577 pts/8    D+             \_ ethtool -s eth0 wol g

many processes were stuck in D:

USER     PID    VSZ   RSS STAT START COMMAND
root   11493      0     0 D    16:11  \_ [kworker/u:15]
nobody  1707  21472   992 D    14:31 dnsmasq --strict-order --bind-interfaces --pid-file=/var/run/libvirt/network/default.pid --conf-file= --except-interface lo --listen-address 192.168.122.1 --dhcp-range 192.168.122.2,192.168.122.254 --dhcp-leasefile=/var/lib/libvirt/dnsmasq/default.leases --dhcp-lease-max=253 --dhcp-no-override
adi    11606  41004  2424 D+   16:13  |       \_ ssh hex
root   11577   4092   324 D+   16:11  |                               \_ ethtool -s eth0 wol g
root   11595  22108   892 D+   16:12  |       \_ sudo cat /proc/11577/stack
root   11604  22108   900 D+   16:13  |       \_ sudo cat /proc/11577/stack

==> /proc/11577/wchan <==
synchronize_sched

-andy