linux-kernel - [char-misc-next 3/8] mei: drop read complete queue emptiness check

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Date:	Thu, 16 Jun 2016 17:58:54 +0300
From:	Tomas Winkler <tomas.winkler@...el.com>
To:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:	Alexander Usyskin <alexander.usyskin@...el.com>,
	linux-kernel@...r.kernel.org,
	Tomas Winkler <tomas.winkler@...el.com>
Subject: [char-misc-next 3/8] mei: drop read complete queue emptiness check

From: Alexander Usyskin <alexander.usyskin@...el.com>

In the course of the read flow we want to wait for read completion only
if the read queue is empty.
However the calling list_empty(&cl->rd_completed) is a duplication as the
same check was performed by mei_cl_read_cb() and the waiting is skipped
if it returns not NULL.

Signed-off-by: Alexander Usyskin <alexander.usyskin@...el.com>
Signed-off-by: Tomas Winkler <tomas.winkler@...el.com>
---
 drivers/misc/mei/bus.c  | 3 ++-
 drivers/misc/mei/main.c | 3 ++-
 2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/misc/mei/bus.c b/drivers/misc/mei/bus.c
index 1f33fea9299f..63411ddfb83d 100644
--- a/drivers/misc/mei/bus.c
+++ b/drivers/misc/mei/bus.c
@@ -126,7 +126,8 @@ ssize_t __mei_cl_recv(struct mei_cl *cl, u8 *buf, size_t length)
 		goto out;
 
 	/* wait on event only if there is no other waiter */
-	if (list_empty(&cl->rd_completed) && !waitqueue_active(&cl->rx_wait)) {
+	/* synchronized under device mutex */
+	if (!waitqueue_active(&cl->rx_wait)) {
 
 		mutex_unlock(&bus->device_lock);
 
diff --git a/drivers/misc/mei/main.c b/drivers/misc/mei/main.c
index a8d0471f817f..3326bde7fba1 100644
--- a/drivers/misc/mei/main.c
+++ b/drivers/misc/mei/main.c
@@ -183,7 +183,8 @@ static ssize_t mei_read(struct file *file, char __user *ubuf,
 		goto out;
 	}
 
-	if (list_empty(&cl->rd_completed) && !waitqueue_active(&cl->rx_wait)) {
+	/* synchronized under device mutex */
+	if (!waitqueue_active(&cl->rx_wait)) {
 		if (file->f_flags & O_NONBLOCK) {
 			rets = -EAGAIN;
 			goto out;
-- 
2.5.5