> On May 5, 2015, at 9:35 AM, Don Zickus <dzickus@xxxxxxxxxx> wrote:
>
>> On Mon, May 04, 2015 at 04:17:07PM -0700, john.hubbard@xxxxxxxxx wrote:
>> From: John Hubbard <jhubbard@xxxxxxxxxx>
>>
>> Commit 8fcf2cc768acd845c1fed837bf9cfe2d7106336d in linux-next
>> introduced a regression in some configurations. Specifically,
>> with CONFIG_NO_HZ_FULL set, and CONFIG_NO_HZ_FULL_ALL *not* set,
>> the kernel will crash in lockup_detector_init(), due to a
>> NULL tick_nohz_full_mask pointer.
>>
>> This is because the above commit uses tick_nohz_full_mask
>> (in lockup_detector_init), if CONFIG_NO_HZ_FULL is set, but
>> tick_nohz_full_mask only gets allocated if either:
>>
>> a) CONFIG_NO_HZ_FULL_ALL is set, or
>>
>> b) Someone passes in nohz_full=<any_value> on the boot
>> args line.
>>
>> To correct this, change lockup_detector_init so that it does
>> a runtime check (in addition to the ifdef check). This now
>> matches the way most of the other CONFIG_NO_HZ_FULL code does
>> it's checking. This fix is a little simpler than my original
>> proposed fix, thanks to Chris Metcalf for that.
>
> Hi Chris,
>
> If you are ok with this, I can forward it along.
>
> Cheers,
> Don
With the new dynamic test, we don't actually need the ifdef anymore. I asked John if he could respin it without that.
>
>>
>> Signed-off-by: John Hubbard <jhubbard@xxxxxxxxxx>
>> ---
>> kernel/watchdog.c | 12 ++++++++----
>> 1 file changed, 8 insertions(+), 4 deletions(-)
>>
>> diff --git a/kernel/watchdog.c b/kernel/watchdog.c
>> index 40fda2f..910d73f 100644
>> --- a/kernel/watchdog.c
>> +++ b/kernel/watchdog.c
>> @@ -921,10 +921,14 @@ void __init lockup_detector_init(void)
>> set_sample_period();
>>
>> #ifdef CONFIG_NO_HZ_FULL
>> - if (!cpumask_empty(tick_nohz_full_mask))
>> - pr_info("Disabling watchdog on nohz_full cores by default\n");
>> - cpumask_andnot(&watchdog_cpumask, cpu_possible_mask,
>> - tick_nohz_full_mask);
>> + if (tick_nohz_full_enabled()) {
>> + if (!cpumask_empty(tick_nohz_full_mask))
>> + pr_info("Disabling watchdog on nohz_full cores by default\n");
>> + cpumask_andnot(&watchdog_cpumask, cpu_possible_mask,
>> + tick_nohz_full_mask);
>> + }
>> + else
>> + cpumask_copy(&watchdog_cpumask, cpu_possible_mask);
>> #else
>> cpumask_copy(&watchdog_cpumask, cpu_possible_mask);
>> #endif
>> --
>> 2.3.7
>>
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