linux-kernel - [PATCH v2 4/9] hyperv: Replace smp_read_barrier_depends() with lockless

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Message-Id: <1416582363-20661-5-git-send-email-bobby.prani@gmail.com>
Date:	Fri, 21 Nov 2014 10:05:58 -0500
From:	Pranith Kumar <bobby.prani@...il.com>
To:	"K. Y. Srinivasan" <kys@...rosoft.com>,
	Haiyang Zhang <haiyangz@...rosoft.com>,
	devel@...uxdriverproject.org (open list:Hyper-V CORE AND...),
	linux-kernel@...r.kernel.org (open list)
Subject: [PATCH v2 4/9] hyperv: Replace smp_read_barrier_depends() with lockless_dereference()

Recently lockless_dereference() was added which can be used in place of
hard-coding smp_read_barrier_depends(). The following PATCH makes the change.

Signed-off-by: Pranith Kumar <bobby.prani@...il.com>
---
 include/linux/hyperv.h | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/include/linux/hyperv.h b/include/linux/hyperv.h
index 08cfaff..06418b1 100644
--- a/include/linux/hyperv.h
+++ b/include/linux/hyperv.h
@@ -127,13 +127,12 @@ hv_get_ringbuffer_availbytes(struct hv_ring_buffer_info *rbi,
 			  u32 *read, u32 *write)
 {
 	u32 read_loc, write_loc, dsize;
-
-	smp_read_barrier_depends();
+	struct hv_ring_buffer_info *rbi_p = lockless_dereference(rbi);
 
 	/* Capture the read/write indices before they changed */
-	read_loc = rbi->ring_buffer->read_index;
-	write_loc = rbi->ring_buffer->write_index;
-	dsize = rbi->ring_datasize;
+	read_loc = rbi_p->ring_buffer->read_index;
+	write_loc = rbi_p->ring_buffer->write_index;
+	dsize = rbi_p->ring_datasize;
 
 	*write = write_loc >= read_loc ? dsize - (write_loc - read_loc) :
 		read_loc - write_loc;
-- 
1.9.1

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