From: Shai Fultheim <shai@scalemp.com>
Date: Thu, 19 Apr 2012 22:12:32 +0000 (+0300)
Subject: x86: Conditionally update time when ack-ing pending irqs
X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=42fa4250436304d4650fa271f37671f6cee24e08;p=linux-beck.git

x86: Conditionally update time when ack-ing pending irqs

On virtual environments, apic_read could take a long time. As a
result, under certain conditions the ack pending loop may exit
without any queued irqs left, but after more than one second. A
warning will be printed needlessly in this case.

If the loop is about to exit regardless of max_loops, don't
update it.

Signed-off-by: Shai Fultheim <shai@scalemp.com>
[ rebased and reworded the commit message]
Signed-off-by: Ido Yariv <ido@wizery.com>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1334873552-31346-1-git-send-email-ido@wizery.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---

diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c
index edc24480469f..3beab627190e 100644
--- a/arch/x86/kernel/apic/apic.c
+++ b/arch/x86/kernel/apic/apic.c
@@ -1325,11 +1325,13 @@ void __cpuinit setup_local_APIC(void)
 			       acked);
 			break;
 		}
-		if (cpu_has_tsc) {
-			rdtscll(ntsc);
-			max_loops = (cpu_khz << 10) - (ntsc - tsc);
-		} else
-			max_loops--;
+		if (queued) {
+			if (cpu_has_tsc) {
+				rdtscll(ntsc);
+				max_loops = (cpu_khz << 10) - (ntsc - tsc);
+			} else
+				max_loops--;
+		}
 	} while (queued && max_loops > 0);
 	WARN_ON(max_loops <= 0);