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

[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 [off-list ref] wrote:

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On Fri, Feb 23, 2018 at 11:00 AM, Randy Dunlap [off-list ref] wrote:

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[adding netdev]

On 02/23/2018 08:05 AM, Khalid Aziz wrote:

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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:

...

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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