Messages in this thread | | | Date | Fri, 29 May 2020 18:15:18 +0200 | From | Sebastian Andrzej Siewior <> | Subject | Re: Kernel crash due to memory corruption with v5.4.26-rt17 and PowerPC e500 |
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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
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