linux-kernel - [PATCH v2] powerpc: handle simultaneous interrupts at once

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Message-Id: <20170316085545.EEE4A68481@localhost.localdomain>
Date:   Thu, 16 Mar 2017 09:55:45 +0100 (CET)
From:   Christophe Leroy <christophe.leroy@....fr>
To:     Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Scott Wood <oss@...error.net>
Cc:     linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Subject: [PATCH v2] powerpc: handle simultaneous interrupts at once

It often happens to have simultaneous interrupts, for instance
when having double Ethernet attachment. With the current
implementation, we suffer the cost of kernel entry/exit for each
interrupt.

This patch introduces a loop in __do_irq() to handle all interrupts
at once before returning.

Signed-off-by: Christophe Leroy <christophe.leroy@....fr>
---
Changed from v1(RFC): simplified following remark from benh

 arch/powerpc/kernel/irq.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/kernel/irq.c b/arch/powerpc/kernel/irq.c
index a018f5cae899..ba0cb6c2ee7d 100644
--- a/arch/powerpc/kernel/irq.c
+++ b/arch/powerpc/kernel/irq.c
@@ -522,7 +522,11 @@ void __do_irq(struct pt_regs *regs)
 	if (unlikely(!irq))
 		__this_cpu_inc(irq_stat.spurious_irqs);
 	else
-		generic_handle_irq(irq);
+		do {
+			generic_handle_irq(irq);
+
+			irq = ppc_md.get_irq();
+		} while (irq);
 
 	trace_irq_exit(regs);
 
-- 
2.12.0