On 01/20/2017 09:09 AM, Sebastian Andrzej Siewior wrote:
> On 2017-01-20 08:32:37 [-0800], Jens Axboe wrote:
>> That's alright, sounds like it's not a -next regression, but rather something
>> that is already broken. I can reproduce a lot of breakage if I enable
>> CONFIG_DEBUG_TEST_DRIVER_REMOVE, in fact my system doesn't boot at all. This
>> is the first bug:
>>
>> [ 18.247895] ------------[ cut here ]------------
>> [ 18.247907] WARNING: CPU: 21 PID: 2223 at drivers/ata/libata-core.c:6522 ata_host_detach+0x11b]
>> [ 18.247908] Modules linked in: igb(+) ahci(+) libahci i2c_algo_bit dca libata nvme(+) nvme_core
>> [ 18.247917] CPU: 21 PID: 2223 Comm: systemd-udevd Tainted: G W 4.10.0-rc4+ #30
>> [ 18.247919] Hardware name: Dell Inc. PowerEdge T630/0NT78X, BIOS 2.3.4 11/09/2016
>> [ 18.247919] Call Trace:
>> [ 18.247928] dump_stack+0x68/0x93
>> [ 18.247934] __warn+0xc6/0xe0
>> [ 18.247937] warn_slowpath_null+0x18/0x20
>> [ 18.247943] ata_host_detach+0x11b/0x120 [libata]
> …
>
>> and it's even more downhill from there. That option is marked unstable, are we
>> expecting it to work right now?
>
> Well, as per 248ff0216543 ("driver core: Make Kconfig text for
> DEBUG_TEST_DRIVER_REMOVE stronger"):
>
> | The current state of driver removal is not great.
> | CONFIG_DEBUG_TEST_DRIVER_REMOVE finds lots of errors. The help text
> | currently undersells exactly how many errors this option will find. Add
> | a bit more description to indicate this option shouldn't be turned on
> | unless you actually want to debug driver removal. The text can be
> | changed later when more drivers are fixed up.
>
> so it looks like the option is working but it uncovers bugs. I've put
> you in TO because the breakage in kvm test went away after I disabled
> the MQ support in SCSI. So I *assumed* that MQ was not doing something
> right in the removal path. I don't know if this libata-core backtrace is
> a false positive or not.
Sure, I get that, my question is just if it's always finding valid bugs,
or if the test itself is buggy. The fact that I can't boot anything after
enabling it makes me suspicious.
Or maybe the state of load/remove/load is just pretty sad.
--
Jens Axboe
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