tech@, visa@,

I think I finally figured out why my small octen is hangs randomly under
load, it was very long week of printf-based debugin.

So, octciu_next_irq() operates on a uint64_t pending interrupt bitmap, and
irq spans the full 0..63 range. Using 1u << irq therefore builds a 32 bit
mask for a 64 bit word; once irq >= 32, the selected pending bit is no
longer cleared correctly.

The immediate consequence is loss of forward progress in the dispatcher
loop: the same interrupt can remain logically pending in the local copy of
isr, the loop can revisit it indefinitely, and the CPU can remain trapped in
interrupt handling.

After I applied that, I can't hang it anymore on my tests.

Ok? Probably it worth to include into 7.9

Index: sys/arch/octeon/dev/octciu.c
===================================================================
RCS file: /home/cvs/src/sys/arch/octeon/dev/octciu.c,v
diff -u -p -r1.20 octciu.c
--- sys/arch/octeon/dev/octciu.c	4 Apr 2026 09:00:20 -0000	1.20
+++ sys/arch/octeon/dev/octciu.c	16 Apr 2026 10:54:54 -0000
@@ -452,7 +452,7 @@ octciu_next_irq(uint64_t *isr)
 	: "=r" (tmp) : "0" (tmp));
 
 	irq = 63u - tmp;
-	*isr &= ~(1u << irq);
+	*isr &= ~(1ULL << irq);
 	return irq;
 }
 


-- 
wbr, Kirill