Overhead of arm64 LSE per-CPU atomics?

[Catalin Marinas]

On Wed, Nov 05, 2025 at 11:47:07AM -0800, Paul E. McKenney wrote:
> On Wed, Nov 05, 2025 at 07:16:42PM +0000, Catalin Marinas wrote:
> > I think we should change the percpu atomics, it makes more sense to do
> > them near, but I'll keep the others as they are. Planning to post a
> > proper patch tomorrow and see if Will NAKs it ;) (I've been in meetings
> > all day). Something like below but with more comments and a commit log:
> 
> I do like fixing this in the arm64 percpu atomics.  However, this gets
> me assembler errors, perhaps because I am using an old version of gcc
> or perhaps because I am still based off of v6.17-rc1:
> 
> 	/tmp/ccYlMkU1.s: Assembler messages:
> 	/tmp/ccYlMkU1.s:9292: Error: invalid addressing mode at operand 2 -- `stadd x2,x4,[x0]'
> 	/tmp/ccYlMkU1.s:9428: Error: invalid addressing mode at operand 2 -- `stadd x3,x6,[x1]'
> 	/tmp/ccYlMkU1.s:9299: Error: attempt to move .org backwards
> 	/tmp/ccYlMkU1.s:9435: Error: attempt to move .org backwards

Are you sure it is applied correctly? There shouldn't be any trace of
stadd in asm/percpu.h.

-- 
Catalin