Re: [PATCH sched_ext/for-7.4] sched_ext: Work around pahole 1.32 dropping scx_bpf_task_set_lazy_resched() from BTF

[Andrea Righi]

On Tue, Sep 29, 2026 at 09:25:02AM -1000, Tejun Heo wrote:
> On Tue, Sep 29, 2026 at 09:19:50PM +0200, Andrea Righi wrote:
> > First of all thanks for figuring this out, it was really annoying, I've been
> > holding pahole to 1.31 because of this.
> > 
> > I also looked a bit and it seems to be triggered specifically by the bool type.
> > This is with clang 22.1.8 on x86_64 without barrier_data and only changing the
> > type:
> > 
> >   bool  movl %esi, %ebp    -> dropped by pahole
> >   u32   movl %esi, %ebp    -> ok
> >   u64   movq %rsi, %r15    -> ok
> > 
> > With u32 the generated code is identical to the bool case, but clang keeps the
> > RSI entry range, so pahole is happy.
> > 
> > Should we just change lazy to u32 (or use a u64 flags) instead of using
> > barrier_data()?
> 
> I mean, bool is the right and I'm hoping clang can be fixed and the
> workaround seems to work, so keep it as-is unless there are other reasons to
> change it (e.g. this becomes a wider interface taking u64 flags or sth like
> that)?

Yeah, at the moment I don't see any valid reason to change lazy to a u64 flags.
And it's probably better to introduce a workaround in the code rather than a
workaround in the ABI, so let's keep barrier_data().

Reviewed-by: Andrea Righi <arighi@xxxxxxxxxx>

Thanks,
-Andrea