On Fri, 14 May 2021 22:16:10 +0200 Thomas Gleixner wrote:

On Fri, May 14 2021 at 11:56, Jakub Kicinski wrote:

quoted

On Thu, 13 May 2021 00:28:02 +0200 Thomas Gleixner wrote:  

quoted

Blame me for that decision.

No matter which variant we end up with, this needs to go into all stable
RT kernels ASAP.  

Mumble mumble. I thought we concluded that drivers used on RT can be
fixed, we've already done it for a couple drivers (by which I mean two).
If all the IRQ handler is doing is scheduling NAPI (which it is for
modern NICs) - IRQF_NO_THREAD seems like the right option.  

Yes. That works, but there are a bunch which do more than that IIRC.

quoted

Is there any driver you care about that we can convert to using
IRQF_NO_THREAD so we can have new drivers to "do the right thing"
while the old ones depend on this workaround for now?  

The start of this thread was about i40e_msix_clean_rings() which
probably falls under the IRQF_NO_THREAD category, but I'm sure that
there are others. So I chose the safe way for RT for now.

Sounds reasonable. I'll send a patch with a new helper and convert 
an example driver I'm sure falls into the "napi_schedule(); return;"
category. I just want to make sure "the right thing to do" is
accessible for people writing new drivers.