Re: [PATCH 00/14] sched: Support shared runqueue locking

[Andrea Righi <arighi@nvidia.com>]

On Wed, Sep 10, 2025 at 08:35:55PM +0200, Peter Zijlstra wrote:
> On Wed, Sep 10, 2025 at 07:32:12PM +0200, Andrea Righi wrote:
> 
> > [   15.160400] Call Trace:
> > [   15.160706]  dequeue_task_scx+0x14a/0x270
> > [   15.160857]  move_queued_task+0x7d/0x2d0
> > [   15.160952]  affine_move_task+0x6ca/0x700
> > [   15.161210]  __set_cpus_allowed_ptr+0x64/0xa0
> > [   15.161348]  __sched_setaffinity+0x72/0x100
> > [   15.161459]  sched_setaffinity+0x261/0x2f0
> > [   15.161569]  __x64_sys_sched_setaffinity+0x50/0x80
> > [   15.161705]  do_syscall_64+0xbb/0x370
> > [   15.161816]  entry_SYSCALL_64_after_hwframe+0x77/0x7f
> > 
> > Are we missing a DEQUEUE_LOCKED in the sched_setaffinity() path?
> 
> Yeah, the affine_move_task->move_queued_task path is messed up. It
> relied on raw_spin_lock_irqsave(&p->pi_lock); rq_lock(rq); being
> equivalent to task_rq_lock(), which is no longer true.
> 
> I fixed a few such sites earlier today but missed this one.
> 
> I'll go untangle it, but probably something for tomorrow, I'm bound to
> make a mess of it now :-)

Sure! I’ll run more tests in the meantime. For now, that's the only issue
I've found. :)

Thanks!
-Andrea