ipipe: Re-read domain data pointer after interrupt handler execution

From: Jan Kiszka <[email protected]>

This caused subtle system corruptions on SMP: The context which took the IRQ may migrate to a different CPU during the execution of the IRQ handler (migration to root domain -> load balancing). So we must refresh the per-CPU domain data and not use the one obtained on entry.

---

Just for early review. I'll send 2.6.38 pull requests for these patches, some more fixes, and access optimizations for ipipe_percpu_domain_data::status next week after running more serious SMP load against them.

Note that this bug affects any ipipe version I've found in git. So the patch should be applied/backported to all versions we still support.

PS: Months of collecting oopses, more than 1 weeks of debugging. Yeah, there were more bugs, but this was likely the toughest monster.

 kernel/ipipe/core.c |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)

index 9aa4800..0ed7751 100644
@@ -1168,6 +1168,7 @@ void __ipipe_dispatch_wired_nocheck(struct ipipe_domain *head, unsigned irq) /*
 	head->irqs[irq].handler(irq, head->irqs[irq].cookie); /* Call the ISR. */
 	__ipipe_run_irqtail(irq);
 	barrier();
+	p = ipipe_cpudom_ptr(head);
 	__clear_bit(IPIPE_STALL_FLAG, &p->status);
 
 	if (__ipipe_current_domain == head) {

1.7.1