Re: [PATCH 3/5] mm/vmstat: use cmpxchg loop in cpu_vm_stats_fold

Christoph Lameter
2023-02-03T09:34:59Z

On Thu, 2 Feb 2023, Marcelo Tosatti wrote:

> > I thought you would only run this while the kernel is not active on the
> > remote cpu? Then you dont need any cmpxchg and you can leave the function
> > as is.
>
> The remote cpu can enter kernel mode while this function executes.

Isnt there some lock/serializtion to stall the kernel until you are done?

> There is no mode which indicates userspace cannot enter the kernel.

There are lot of thinngs that happen upon entry to the kernel. I would
hope that you can do something there. Scheduler?