Re: [PATCH] parisc: Try to fix random segmentation faults in package builds

[John David Anglin <dave.anglin@bell.net>]

On 2024-06-04 11:07 a.m., matoro wrote:
>> Thanks a ton Dave, I've applied this on top of 6.9.2 and also think I'm seeing improvement!  No panics yet, I have a couple week's worth of 
>> package testing to catch up on so I'll report if I see anything!
>
> I've seen a few warnings in my dmesg while testing, although I didn't see any immediately corresponding failures.  Any danger?
We have determined most of the warnings arise from pages that have been swapped out.  Mostly, it seems these
pages have been flushed to memory before the pte is changed to a swap pte.  There might be issues for pages that
have been cleared.  It is possible the random faults aren't related to the warning I added for pages with an invalid pfn
in flush_cache_page_if_present.  The only thing I know for certain is there is no way to flush these pages on parisc
other than flushing the whole cache.

My c8000 has run almost two weeks without any random faults.  On the other hand, Helge has two machines that
frequently fault and generate these warnings.

Flushing the whole cache in flush_cache_mm and flush_cache_range might eliminate the random faults but
there will be a significant performance hit.

Dave

-- 
John David Anglin  dave.anglin@bell.net