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

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Date:   Tue, 4 Jan 2022 16:26:57 -0300
From:   Walter Lozano <walter.lozano@...labora.com>
To:     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 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 


-- 
Walter Lozano
Collabora Ltd.