linux-kernel - Re: Occasional hung with UM after enable VMAP

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Message-ID: <5c9b8e61-1158-1004-8280-04cc3c921ad1@collabora.com>
Date:   Wed, 5 Jan 2022 09:59:25 -0300
From:   Walter Lozano <walter.lozano@...labora.com>
To:     Anton Ivanov <anton.ivanov@...-begemot.co.uk>,
        Johannes Berg <johannes@...solutions.net>,
        linux-um@...ts.infradead.org, linux-kernel@...r.kernel.org
Cc:     Sjoerd Simons <sjoerd.simons@...labora.com>,
        ritesh sarraf <ritesh.sarraf@...labora.com>
Subject: Re: Occasional hung with UM after enable VMAP_STACK

Hi Anton,

On 1/4/22 18:39, Anton Ivanov wrote:
> On 04/01/2022 19:26, Walter Lozano wrote:
>> Hi Johannes,
>>
>> On 1/4/22 16:04, Johannes Berg wrote:
>>> On Tue, 2022-01-04 at 15:10 -0300, Walter Lozano wrote:
>>>> Hi all,
>>>>
>>>> I noticed that after "um: enable VMAP_STACK" [1] I experienced some
>>>> occasional hung in my Gitlab CI jobs that use user-mode-linux to build
>>>> distro images.
>>>>
>>> Did you actually *enable* VMAP_STACK in the config as well? The commit
>>> just makes it *possible* to enable it, you still have to set it
>>> yourself. So you should be able to easily check with/without that
>>> setting.
>>
>> Thank you for your quick response. The Debian configuration on 
>> package user-mode-linux have these settings
>>
>> CONFIG_HAVE_ARCH_VMAP_STACK=y
>> CONFIG_VMAP_STACK=y
>>
>>
>> as you can see in [1]. I did run some tests disabling those settings, 
>> which passed without any hung.
>>
>> Unfortunately the "occasional" behavior makes this issue a bit tricky 
>> to debug.
>>
>> Regards,
>>
>> Walter
>>
>> [1] 
>> https://salsa.debian.org/uml-team/user-mode-linux/-/blob/master/config.amd64#L321 
>>
>>
>
> Just to narrow things down - 64 bit or 32 bit?
>
Thank you for commenting on this thread. All my tests were done with 64 
bits.

Regards,

-- 
Walter Lozano
Collabora Ltd.