From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To: Mark Marshall <markmarshall14@gmail.com>
Cc: linux-rt-users <linux-rt-users@vger.kernel.org>,
Mark Marshall <mark.marshall@omicronenergy.com>,
thomas.graziadei@omicronenergy.com,
Thomas Gleixner <tglx@linutronix.de>,
linux-kernel@vger.kernel.org, rostedt@goodmis.org
Subject: Re: Kernel crash due to memory corruption with v5.4.26-rt17 and PowerPC e500
Date: Fri, 29 May 2020 18:15:18 +0200 [thread overview]
Message-ID: <20200529161518.svpxhkeljafbtdz2@linutronix.de> (raw)
In-Reply-To: <CAD4b4WLS36JKepz31m98Z3Ve05d63GnfBGsuuWRXpjXZqPoBrA@mail.gmail.com>
On 2020-05-29 17:38:39 [+0200], Mark Marshall wrote:
> Hi Sebastian & list,
Hi,
> I had assumed that my e-mail had got lost or overlooked, I was meaning to
> post a follow up message this week...
>
> All I could find from the debugging and tracing that we added was that
> something was going wrong with the mm data structures somewhere in the
> exec code. In the end I just spent a week or two pouring over the diffs
> of this code between the versions that I new worked and didn't work.
>
> I eventually found the culprit. On the working kernel versions there is
> a patch called "mm: Protect activate_mm() by preempt_[disable&enable]_rt()".
> This is commit f0b4a9cb253a on the V4.19.82-rt30 branch, for instance.
> Although the commit message talks about ARM, it seems that we need this for
> PowerPC too (I guess, any PowerPC with the "nohash" MMU?).
Could you drop me your config, please? I need to dig here a little and I
should have seen this on qemu, right?
> Could you please add this commit back to the RT branch? I'm not sure how
> to find out the history of this commit. For instance, why has it been
> removed from the RT patchset? How are these things tracked, generally?
I dropped that patch in v5.4.3-rt1. I couldn't reproduce the issue that
was documented in the patch and the code that triggered the warning was
removed / reworked in commit
b5466f8728527 ("ARM: mm: remove IPI broadcasting on ASID rollover")
So it looked like no longer needed and then got dropped during the
rebase.
In order to get it back into the RT queue I need to understand why it is
required. What exactly is it fixing. Let me stare at for a little…
> Best regards,
> Mark
Sebastian
next prev parent reply other threads:[~2020-05-29 16:15 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-04 9:40 Kernel crash due to memory corruption with v5.4.26-rt17 and PowerPC e500 Mark Marshall
2020-05-29 13:14 ` Sebastian Andrzej Siewior
2020-05-29 15:38 ` Mark Marshall
2020-05-29 16:15 ` Sebastian Andrzej Siewior [this message]
2020-05-29 16:37 ` Sebastian Andrzej Siewior
2020-07-06 16:50 ` Sebastian Andrzej Siewior
2020-07-10 10:59 ` Thomas Graziadei
2020-08-12 12:45 ` Thomas Graziadei
2020-08-19 7:11 ` 'Sebastian Andrzej Siewior'
2020-09-01 7:41 ` 'Sebastian Andrzej Siewior'
2020-05-29 19:03 ` Mark Marshall
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