linux-kernel - [PATCH 1/3] x86: UV BAU destination timeout period

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Message-ID: <20120622131212.GA31884@sgi.com>
Date:	Fri, 22 Jun 2012 08:12:12 -0500
From:	Cliff Wickman <cpw@....com>
To:	linux-kernel@...r.kernel.org
Cc:	mingo@...e.hu, x86@...nel.org
Subject: [PATCH 1/3] x86: 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>
---
 arch/x86/platform/uv/tlb_uv.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

Index: linux/arch/x86/platform/uv/tlb_uv.c
===================================================================
--- linux.orig/arch/x86/platform/uv/tlb_uv.c
+++ linux/arch/x86/platform/uv/tlb_uv.c
@@ -1811,8 +1811,8 @@ static int calculate_destination_timeout
 		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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