On 02/15/2016 11:01 AM, Tony Lindgren wrote:
* Rafael J. Wysocki <rafael@xxxxxxxxxx> [160215 10:44]:
On Mon, Feb 15, 2016 at 6:05 PM, Guenter Roeck <linux@xxxxxxxxxxxx> wrote:
Rafael,
Hi,
Thanks for the report!
I see crashes in various arm qemu tests due to 'cpufreq: governor: Replace
timers with utilization update callbacks' with next-20160215. An example
crash log and bisect results are attached below.
Please let me know if there is anything I can do to help tracking down
the problem.
It looks like we've uncovered some nastiness in the arch ARM code (see below).
[cut]
[ 1.340000] Unable to handle kernel NULL pointer dereference at virtual address 00000000
[ 1.340000] pgd = c0204000
[ 1.340000] [00000000] *pgd=00000000
[ 1.340000] Internal error: Oops: 80000005 [#1] SMP ARM
[ 1.340000] Modules linked in:
[ 1.340000] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 4.5.0-rc4-next-20160215 #1
[ 1.340000] Hardware name: Generic OMAP3-GP (Flattened Device Tree)
[ 1.340000] task: cb060000 ti: cb05a000 task.ti: cb05a000
[ 1.340000] PC is at 0x0
[ 1.340000] LR is at arch_send_call_function_single_ipi+0x34/0x38
Since this is ARM, arch_send_call_function_single_ipi() looks like this:
void arch_send_call_function_single_ipi(int cpu)
{
smp_cross_call(cpumask_of(cpu), IPI_CALL_FUNC_SINGLE);
}
so I'm not sure how the NULL pointer deref is possible even.
The only thing coming to mind would be that cpumask_of(cpu) triggers
this, but I'm not sure how exactly that can happen.
I need help from somebody who knows how this low-level stuff works on ARM.
That's not even an SMP machine? I suspect a bunch of out of the
65 boot failures here are related to this:
https://kernelci.org/boot/all/job/next/kernel/next-20160215/
The SMP ones seem to fail with some regulator issues?
There is another problem, introduced with 6a0712f6f199e ("PM / OPP: Add
dev_pm_opp_set_rate()"). The kernelci boot log for next-20160212:omap3-overo-tobi
and others experience that problem.
Essentially, the code now assumes that a CPU clock always has a voltage
regulator attached to it, which is not correct. I sent out a patch to fix
that problem a minute ago.
Guenter
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