linux-kernel - [tip:x86/uv] x86/uv: Fix the UV BAU destination timeout period

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Message-ID: <tip-11cab711f686893f2696a061dfca30454a624784@git.kernel.org>
Date:	Mon, 25 Jun 2012 22:59:05 -0700
From:	tip-bot for Cliff Wickman <cpw@....com>
To:	linux-tip-commits@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, hpa@...or.com, mingo@...nel.org,
	cpw@....com, tglx@...utronix.de
Subject: [tip:x86/uv] x86/uv: Fix the UV BAU destination timeout period

Commit-ID:  11cab711f686893f2696a061dfca30454a624784
Gitweb:     http://git.kernel.org/tip/11cab711f686893f2696a061dfca30454a624784
Author:     Cliff Wickman <cpw@....com>
AuthorDate: Fri, 22 Jun 2012 08:12:12 -0500
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Mon, 25 Jun 2012 14:45:04 +0200

x86/uv: Fix the UV BAU destination timeout period

Correct the calculation of a destination timeout period, which
is used to distinguish between a destination timeout and the
situation where all the target software ack resources are full
and a request is returned immediately.

The problem is that integer arithmetic was overflowing, yielding
a very large result.

Without this fix destination timeouts are identified as resource
'plugged' events and an ipi method of resource releasing is
unnecessarily employed.

Signed-off-by: Cliff Wickman <cpw@....com>
Link: http://lkml.kernel.org/r/20120622131212.GA31884@sgi.com
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 arch/x86/platform/uv/tlb_uv.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86/platform/uv/tlb_uv.c b/arch/x86/platform/uv/tlb_uv.c
index 59880af..0c48d43 100644
--- a/arch/x86/platform/uv/tlb_uv.c
+++ b/arch/x86/platform/uv/tlb_uv.c
@@ -1811,8 +1811,8 @@ static int calculate_destination_timeout(void)
 		index = (mmr_image >> BAU_URGENCY_7_SHIFT) & BAU_URGENCY_7_MASK;
 		mmr_image = uv_read_local_mmr(UVH_TRANSACTION_TIMEOUT);
 		mult2 = (mmr_image >> BAU_TRANS_SHIFT) & BAU_TRANS_MASK;
-		base = timeout_base_ns[index];
-		ts_ns = base * mult1 * mult2;
+		ts_ns = timeout_base_ns[index];
+		ts_ns *= (mult1 * mult2);
 		ret = ts_ns / 1000;
 	} else {
 		/* 4 bits  0/1 for 10/80us base, 3 bits of multiplier */
--
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