From 676bcd5d0245afba6b723e4d1bf4a65692fa986d Mon Sep 17 00:00:00 2001
From: "Bjoern B. Brandenburg" <bbb@cs.unc.edu>
Date: Mon, 25 Jul 2011 15:31:34 -0400
Subject: ftdev: don't hold lock while sleeping

Holding the lock prevents other tasks from opening the device.
---
 litmus/ftdev.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/litmus/ftdev.c b/litmus/ftdev.c
index 06fcf4cf77dc..99bc39ffbcef 100644
--- a/litmus/ftdev.c
+++ b/litmus/ftdev.c
@@ -230,13 +230,20 @@ static ssize_t ftdev_read(struct file *filp,
 			 * here with copied data because that data would get
 			 * lost if the task is interrupted (e.g., killed).
 			 */
+			mutex_unlock(&ftdm->lock);
 			set_current_state(TASK_INTERRUPTIBLE);
+
 			schedule_timeout(50);
+
 			if (signal_pending(current)) {
 				if (err == 0)
 					/* nothing read yet, signal problem */
 					err = -ERESTARTSYS;
-				break;
+				goto out;
+			}
+			if (mutex_lock_interruptible(&ftdm->lock)) {
+				err = -ERESTARTSYS;
+				goto out;
 			}
 		} else if (copied < 0) {
 			/* page fault */
-- 
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