Re: Kernel panic with 4.16-rc1 (and 4.16-rc2) running selftest

From: Randy Dunlap
Date: Fri Feb 23 2018 - 19:27:13 EST


[add Matthew Wilcox; hopefully he can look/see]

On 02/23/2018 04:13 PM, Cong Wang wrote:
> On Fri, Feb 23, 2018 at 3:27 PM, Cong Wang <xiyou.wangcong@xxxxxxxxx> wrote:
>> On Fri, Feb 23, 2018 at 11:00 AM, Randy Dunlap <rdunlap@xxxxxxxxxxxxx> wrote:
>>> [adding netdev]
>>>
>>> On 02/23/2018 08:05 AM, Khalid Aziz wrote:
>>>> I am seeing a kernel panic with 4.16-rc1 and 4.16-rc2 kernels when running selftests
>>>> from tools/testing/selftests. Last messages from selftest before kernel panic are:
>>>>
>> ...
>>>> Same selftest does not cause panic on 4.15. git bisect pointed to commit 6ce711f2750031d12cec91384ac5cfa0a485b60a ("idr: Make 1-based IDRs more efficient").
>>>> Kernel config is attached.
>>
>> Looks like something horribly wrong with u32 key id idr...
>
> Adding a few printk's, I got:
>
> [ 31.231560] requested handle = ffe00000
> [ 31.232426] allocated handle = 0
> ...
> [ 31.246475] requested handle = ffd00000
> [ 31.247555] allocated handle = 1
>
>
> So the bug is here where we can't allocate a specific handle:
>
> err = idr_alloc_u32(&tp_c->handle_idr, ht, &handle,
> handle, GFP_KERNEL);
> if (err) {
> kfree(ht);
> return err;
> }
>


--
~Randy