[PATCH] Fix staging:iio:ring_sw: Fix incorrect test on successful read of last value, causes infinite loop

[PATCH] Fix staging:iio:ring_sw: Fix incorrect test on successful read of last value, causes infinite loop

[Jonathan Cameron]

Signed-off-by: Jonathan Cameron <jic23@cam.ac.uk>
---

 This is a bad one. The test means that almost no reads of the last
 value ever succeed!  Result is an infinite loop.

 Another one for the 'oops' category.

 Patch is post the spin lock fix:
 [PATCH] Staging: IIO: Fix uses of spinlocks prior to init in ring implementations


 drivers/staging/iio/ring_sw.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/drivers/staging/iio/ring_sw.c b/drivers/staging/iio/ring_sw.c
index 7dff2bf..5abba8c 100644
--- a/drivers/staging/iio/ring_sw.c
+++ b/drivers/staging/iio/ring_sw.c
@@ -296,7 +296,7 @@ again:
 		return -EAGAIN;
 	memcpy(data, last_written_p_copy, ring->buf.bpd);
 
-	if (unlikely(ring->last_written_p >= last_written_p_copy))
+	if (unlikely(ring->last_written_p != last_written_p_copy))
 		goto again;
 
 	iio_unmark_sw_rb_in_use(&ring->buf);
-- 
1.6.4.4

patch staging-iio-ring_sw-fix-incorrect-test-on-successful-read-of-last-value-causes-infinite-loop.patch added to gregkh-2.6 tree

[gregkh]

This is a note to let you know that I've just added the patch titled

    Subject: staging: iio: ring_sw: Fix incorrect test on successful read=
 of last value, causes infinite loop

to my gregkh-2.6 tree.  Its filename is

    staging-iio-ring_sw-fix-incorrect-test-on-successful-read-of-last-val=
ue-causes-infinite-loop.patch

This tree can be found at=20
    http://www.kernel.org/pub/linux/kernel/people/gregkh/gregkh-2.6/patch=
es/


>>From jic23@cam.ac.uk  Thu Apr 22 16:41:09 2010
From: Jonathan Cameron <jic23@cam.ac.uk>
Date: Tue, 30 Mar 2010 17:45:04 +0100
Subject: staging: iio: ring_sw: Fix incorrect test on successful read of =
last value, causes infinite loop
To: "linux-iio@vger.kernel.org" <linux-iio@vger.kernel.org>, Greg Kroah-H=
artman <gregkh@suse.de>
Message-ID: <4BB22A90.6070801@cam.ac.uk>


This is a bad one. The test means that almost no reads of the last
value ever succeed!  Result is an infinite loop.

Another one for the 'oops' category.

Signed-off-by: Jonathan Cameron <jic23@cam.ac.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
 drivers/staging/iio/ring_sw.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/staging/iio/ring_sw.c
+++ b/drivers/staging/iio/ring_sw.c
@@ -293,7 +293,7 @@ again:
 		return -EAGAIN;
 	memcpy(data, last_written_p_copy, ring->buf.bpd);
=20
-	if (unlikely(ring->last_written_p >=3D last_written_p_copy))
+	if (unlikely(ring->last_written_p !=3D last_written_p_copy))
 		goto again;
=20
 	iio_unmark_sw_rb_in_use(&ring->buf);