linux-kernel - [PATCH 3/5] logger: reorder prepare_to_wait and mutex

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Date:	Tue, 7 Feb 2012 18:30:09 -0800
From:	Tim Bird <tim.bird@...sony.com>
To:	Greg KH <gregkh@...uxfoundation.org>,
	linux-embedded <linux-embedded@...r.kernel.org>,
	linux kernel <linux-kernel@...r.kernel.org>,
	Brian Swetland <swetland@...gle.com>,
	Dima Zavin <dima@...roid.com>, Andrew Morton <akpm@...l.org>
Subject: [PATCH 3/5] logger: reorder prepare_to_wait and mutex_lock

If mutex_lock waits, it will return in state TASK_RUNNING,
rubbing out the effect of prepare_to_wait().

Signed-off-by: Tim Bird <tim.bird@...sony.com>
---
 drivers/staging/android/logger.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/drivers/staging/android/logger.c b/drivers/staging/android/logger.c
index 92cfd94..54b7cdf 100644
--- a/drivers/staging/android/logger.c
+++ b/drivers/staging/android/logger.c
@@ -172,9 +172,10 @@ static ssize_t logger_read(struct file *file, char __user *buf,

 start:
 	while (1) {
+		mutex_lock(&log->mutex);
+
 		prepare_to_wait(&log->wq, &wait, TASK_INTERRUPTIBLE);

-		mutex_lock(&log->mutex);
 		ret = (log->w_off == reader->r_off);
 		mutex_unlock(&log->mutex);
 		if (!ret)
-- 
1.7.2.3

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