Re: [Regression 5.7-rc1] Random hangs on 32-bit PowerPC (PowerBook6, 7)

On Mon, 18 May 2020 at 18:15, Christophe Leroy
[off-list ref] wrote:

Yeah I discovered recently that the way swap is implemented on powerpc
expects RW and other important bits not be one of the 3 least
significant bits (see __pte_to_swp_entry() )

I see, you get the swap entry by shifting the PTE right three bits.

I guess the easiest for the time being is to revert the commit with a
proper explanation of the issue, then one day we'll modify the way
powerpc manages swap.

I wonder, what issues could be observable by reverting? I'm asking
this because I've seen another hang on Linux 5.6, but it's harder to
trigger and it involves the GPU (I usually reproduce it easily by,
say, running Arctic Fox and starting a simple OpenGL game like
Chromium BSU). Of course, since this is PowerPC with AGP (even though
I have the AGP GART disabled), it's most likely something unrelated.