Re: [RFC PATCH kernel] powerpc/xive: Drop deregistered irqs

On 12/07/2019 18:29, Benjamin Herrenschmidt wrote:

On Fri, 2019-07-12 at 18:20 +1000, Alexey Kardashevskiy wrote:

quoted

diff --git a/arch/powerpc/sysdev/xive/common.c b/arch/powerpc/sysdev/xive/common.c
index 082c7e1c20f0..65742e280337 100644
--- a/arch/powerpc/sysdev/xive/common.c
+++ b/arch/powerpc/sysdev/xive/common.c

@@ -148,8 +148,12 @@ static u32 xive_scan_interrupts(struct xive_cpu *xc, bool just_peek)
  		irq = xive_read_eq(&xc->queue[prio], just_peek);
  
  		/* Found something ? That's it */
-		if (irq)
-			break;
+		if (irq) {
+			/* Another CPU may have shut this irq down, check it */
+			if (irq_to_desc(irq))

What if it gets deregistered here .... ?

Yeah that is the problem.

quoted

+				break;
+			irq = 0;
+		}
  
  		/* Clear pending bits */
  		xc->pending_prio &= ~(1 << prio);

Wouldn't it be better to check the return value from generic_handle_irq
instead ?

Where exactly, here?
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/powerpc/kernel/irq.c#n614

If so, then in order to do EOI, I'll need the desc which is gone, or I am missing the point?


-- 
Alexey