Re: RFC: remove set_fs for m68k

[Michael Schmitz <schmitzmic@gmail.com>]

Hi Christoph,

On 15/07/21 7:26 am, Michael Schmitz wrote:
> I've got a vague recollection that I've seen weird crashes in the past 
> related to temperature extremes (we've had a few unusually cold days 
> in our parts just now), so I've gone back to a kernel from the switch 
> stack / refactoring exit tests (which ran the stress tests fine 
> earlier) to rule that one out. Looking good so far, so I begin to 
> wonder whether we need to introduce get_fc() and use that to restore 
> the original sfc/dfc instead of assuming USER_DATA is always correct?

No crashes with the known good kernel after over a day of stress testing 
- I'll try Andreas' patch once the current test run has completed.

One thing I noticed with either your final or your v2 patch series - as 
far as the tests ran at all, run times were 30% increased. That's a lot 
more than I would have expected. Large byte size user copies were 
already handled by the code in arch/m68k/lib/uaccess.c which wasn't 
explicitly inlined though the calling raw_copy_to/from_user() was. Could 
the change to no longer inline raw_copy_to/from_user() have such a large 
impact?

Cheers,

     Michael