linux-kernel - [PATCH] block: reduce spin

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Date:	Thu, 19 May 2011 22:43:09 -0400
From:	Eduardo Silva <edsiper@...il.com>
To:	Mike Miller <mike.miller@...com>
Cc:	iss_storagedev@...com, linux-kernel@...r.kernel.org
Subject: [PATCH] block: reduce spin_lock critical region

the critical region is originally composed by a conditional plus
a memory copy, the memory copy routine don't need protection.
Moving the memcpy() outside the conditional also help to fix the
16 compiler warning messages generated in __u8 sn[16] def.

Signed-off-by: Eduardo Silva <edsiper@...il.com>
---
 drivers/block/cciss.c |   19 +++++++++----------
 1 files changed, 9 insertions(+), 10 deletions(-)

diff --git a/drivers/block/cciss.c b/drivers/block/cciss.c
index 9bf1398..199b35e 100644
--- a/drivers/block/cciss.c
+++ b/drivers/block/cciss.c
@@ -621,20 +621,19 @@ static ssize_t dev_show_unique_id(struct device *dev,
 	spin_lock_irqsave(&h->lock, flags);
 	if (h->busy_configuring)
 		ret = -EBUSY;
-	else
-		memcpy(sn, drv->serial_no, sizeof(sn));
 	spin_unlock_irqrestore(&h->lock, flags);
 
 	if (ret)
 		return ret;
-	else
-		return snprintf(buf, 16 * 2 + 2,
-				"%02X%02X%02X%02X%02X%02X%02X%02X"
-				"%02X%02X%02X%02X%02X%02X%02X%02X\n",
-				sn[0], sn[1], sn[2], sn[3],
-				sn[4], sn[5], sn[6], sn[7],
-				sn[8], sn[9], sn[10], sn[11],
-				sn[12], sn[13], sn[14], sn[15]);
+
+	memcpy(sn, drv->serial_no, sizeof(sn));
+	return snprintf(buf, 16 * 2 + 2,
+			"%02X%02X%02X%02X%02X%02X%02X%02X"
+			"%02X%02X%02X%02X%02X%02X%02X%02X\n",
+			sn[0], sn[1], sn[2], sn[3],
+			sn[4], sn[5], sn[6], sn[7],
+			sn[8], sn[9], sn[10], sn[11],
+			sn[12], sn[13], sn[14], sn[15]);
 }
 static DEVICE_ATTR(unique_id, S_IRUGO, dev_show_unique_id, NULL);
 
-- 
1.7.4.1



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