linux-kernel - [PATCH 4.13 14/85] parisc: Fix detection of nonsynchronous cr16 cycle counters

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Date:   Tue, 24 Oct 2017 15:06:48 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Helge Deller <deller@....de>
Subject: [PATCH 4.13 14/85] parisc: Fix detection of nonsynchronous cr16 cycle counters

4.13-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Helge Deller <deller@....de>

commit 8642b31ba9eef8a01845146a26682d4869e62513 upstream.

For CPUs which have an unknown or invalid CPU location (physical location)
assume that their cycle counters aren't syncronized across CPUs.

Signed-off-by: Helge Deller <deller@....de>
Fixes: c8c3735997a3 ("parisc: Enhance detection of synchronous cr16 clocksources")
Signed-off-by: Helge Deller <deller@....de>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 arch/parisc/kernel/time.c |    5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

--- a/arch/parisc/kernel/time.c
+++ b/arch/parisc/kernel/time.c
@@ -253,7 +253,10 @@ static int __init init_cr16_clocksource(
 		cpu0_loc = per_cpu(cpu_data, 0).cpu_loc;
 
 		for_each_online_cpu(cpu) {
-			if (cpu0_loc == per_cpu(cpu_data, cpu).cpu_loc)
+			if (cpu == 0)
+				continue;
+			if ((cpu0_loc != 0) &&
+			    (cpu0_loc == per_cpu(cpu_data, cpu).cpu_loc))
 				continue;
 
 			clocksource_cr16.name = "cr16_unstable";