easy kernel crash on TC2 with mainline kernel - linaro-kernel

21 Nov 2013


      I've been banging my head on this one for quite a while now.  The 
problem is that there is very little debug out put available.  Could you 
see if you get the same?
Mainline kernel (I'm using commit 527d151131 right now but older kernels 
are also affected).  Most interesting config options:
CONFIG_BL_SWITCHER=n
CONFIG_ARCH_VEXPRESS_TC2_PM=y
CONFIG_ARM_BIG_LITTLE_CPUIDLE=y
CONFIG_ARM_BIG_LITTLE_CPUFREQ=y
CONFIG_ARM_VEXPRESS_SPC_CPUFREQ=y
To crash the kernel within 5 seconds:
#!/bin/bash
echo 0 > /sys/kernel/bL_switcher/active
sleep 1
while true; do
  for i in 0 1 2 3
  do echo 0 > /sys/devices/system/cpu/cpu$i/online
  done
  for i in 3 2 1 0
  do echo 1 > /sys/devices/system/cpu/cpu$i/online
  done
  for i in 4 3 2 1
  do echo 0 > /sys/devices/system/cpu/cpu$i/online
  done
  for i in 1 2 3 4
  do echo 1 > /sys/devices/system/cpu/cpu$i/online
  done
done
What I get is:
[...]
CPU1: Booted secondary processor
CPU0: Booted secondary processor
Unable to handle kernel NULL pointer dereference at virtual address 0000000c
pgd = c0004000
[ the output stops there ]
The last CPU to be booted up is not always the same.
Are you able to reproduce?
Nicolas