On Wednesday, December 13, 2017 10:06:40 PM CET Thomas Gleixner wrote: > On Wed, 13 Dec 2017, Thomas Gleixner wrote: > > On Wed, 13 Dec 2017, Thomas Gleixner wrote: > > > On Wed, 13 Dec 2017, Linus Torvalds wrote: > > > > > > > On Wed, Dec 13, 2017 at 8:41 AM, Thomas Gleixner <t...@linutronix.de> > > > > wrote: > > > > > > > > > > Definitely. That was fragile forever but puzzles me is that I can't > > > > > figure > > > > > out what now causes that spurious interrupt to surface out of the > > > > > blue. > > > > > > > > Perhaps just timing? > > > > > > That's what I'm trying to figure out right now, because that is the only > > > sensible explanation left. The whole machinery of suspend is exactly the > > > same with and without the vector changes. I instrumented all functions > > > involved and the picture is the same. I even do not see any fundamental > > > timing differences where one would say: That's it. > > > > > > What puzzles me even more is that in the range of commits I'm fiddling > > > with > > > there is no other change than the vector management stuff and the point > > > where it breaks makes no sense at all. The point Maarten bisected it to > > > works nicely here, so that might just point to a very subtle timing issue. > > > > After doing more debugging on this it turns out that this looks like a > > legacy interrupt coming in. The vector number is always 55, which is legacy > > IRQ 7 as seen from the PIC. The corresponding IOAPIC interrupt pin is > > masked and vector 55 is completely unused. > > > > More questions than answers. Still investigating. > > And it does not explain Maartens report which gets a spurious vector 33 on > CPU4 after the non boot cpus have been brought online again. And that's the > vector which was assigned before the affinity was moved by unplugging CPU4. > > Hrmpf. Even more mystery to solve.
Any chance to look at /proc/interrupts from a machine where that can be reproduced? I'm also curious if that can be reproduced by doing CPU offline/online without suspending?