On Sun, 17 Feb 2019, Ming Lei wrote:

On Sat, Feb 16, 2019 at 06:13:13PM +0100, Thomas Gleixner wrote:

quoted

Some drivers need an extra set of interrupts which should not be marked
managed, but should get initial interrupt spreading.

Could you share the drivers and their use case?

You were Cc'ed on that old discussion:

 https://lkml.kernel.org/r/300d6fef733ca76ced581f8c6304bac6@mail.gmail.com

quoted

For both interrupt sets the interrupts are properly spread out, but the
second set is not marked managed.

Given drivers only care the managed vs non-managed interrupt numbers,
just wondering why this case can't be covered by .pre_vectors &
.post_vectors?

Well, yes, but post/pre are not subject to spreading and I really don't
want to go there.

Also this kind of usage may break blk-mq easily, in which the following
rule needs to be respected:

1) all CPUs are required to spread among each interrupt set

2) no any CPU is shared between two IRQs in same set.

I don't see how that would break blk-mq. The unmanaged set is not used by
the blk-mq stuff, that's some driver internal voodoo. So blk-mq still gets
a perfectly spread and managed interrupt set for the queues.

quoted

 	for (i = 0, usedvecs = 0; i < affd->nr_sets; i++) {
-		unsigned int this_vecs = affd->set_size[i];
+		bool managed = affd->unmanaged_sets & (1U << i) ? true : false;

The above check is inverted.

Doh. Stupid me.

Thanks,

	tglx