linux-kernel - Re: "mm/vmalloc: Add flag for freeing of special permsissions" broke udev on ia64

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Date:   Wed, 12 Aug 2020 04:50:17 +0000
From:   "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>
To:     "glaubitz@...sik.fu-berlin.de" <glaubitz@...sik.fu-berlin.de>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "linux-ia64@...r.kernel.org" <linux-ia64@...r.kernel.org>,
        "Luck, Tony" <tony.luck@...el.com>,
        "frank.scheiner@....de" <frank.scheiner@....de>,
        "jrtc27@...c27.com" <jrtc27@...c27.com>,
        "slyfox@...too.org" <slyfox@...too.org>,
        "matorola@...il.com" <matorola@...il.com>
Subject: Re: "mm/vmalloc: Add flag for freeing of special permsissions" broke
 udev on ia64

On Tue, 2020-08-11 at 23:54 +0200, John Paul Adrian Glaubitz wrote:
> Hi Rick!
> 
> I have been bisecting some regressions on ia64 and one problem I ran
> into is that
> udev is causing the kernel to crash after the following change from
> 2019:
> 
> commit 868b104d7379e28013e9d48bdd2db25e0bdcf751
> Author: Rick Edgecombe <rick.p.edgecombe@...el.com>
> Date:   Thu Apr 25 17:11:36 2019 -0700
> 
>     mm/vmalloc: Add flag for freeing of special permsissions
> 
> With your patch applied, udev crashes on ia64 when trying to load
> modules, I'm pasting
> the whole boot message sequence below.
> 
> Any idea what could cause this problem on ia64?
> 
> Thanks,
> Adrian
> 

Hi,

On non-x86, this patchset shouldn't have changed much, just always
flush the TLB and purge the vmalloc area in cases where previously this
would only happen intermittently. Despite this, it also caused a
problem on sparc. In the end the sparc issue turned out to be an issue
with sparc's kernel range TLB flush implementation that was just now
being hit earlier during boot instead of after the system had been up
for some time. So I'm at first wondering if there might be something
like that uncovered here.

Unfortunately, it's unlikely that I can get access to ia64 hardware in
the near term to debug. Would you be able to test some debug patches?
Also, can you post your config?

Thanks,

Rick