Subject: Re: [REGRESSION] rseq: refactoring in v6.19 broke everyone on arm64 and tcmalloc everywhere

From: Thomas Gleixner <[email-masked]>
Date: Fri, 24 Apr 2026 21:44:16 +0200

On Fri, Apr 24 2026 at 17:03, Peter Zijlstra wrote:
> On Fri, Apr 24, 2026 at 04:16:08PM +0200, Thomas Gleixner wrote:
>> > I was really hoping that we would only need to do the "redundant"
>> > cpu_id_start writes would only be needed on membarrier_rseq IPIs where
>> > it really is a pay-for-what-you-use functionality,
>> 
>> That's fine and can be solved without adding this sequence overhead into
>> the scheduler hotpath.
>
> Something like so? (probably needs help for !GENERIC bits)

Yes and yes :)

Let me stare at that !generic tif bits case.