From aa9938973e1410c34500992ff304c131f6fde9b2 Mon Sep 17 00:00:00 2001
From: Con Kolivas <kernel@kolivas.org>
Date: Tue, 5 Nov 2013 09:08:52 +1100
Subject: [PATCH] Use only a trylock in flush queue to prevent deadlocks.

---
 cgminer.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/cgminer.c b/cgminer.c
index bd5a7ed2..d1046459 100644
--- a/cgminer.c
+++ b/cgminer.c
@@ -6614,7 +6614,13 @@ static void flush_queue(struct cgpu_info *cgpu)
 {
 	struct work *work = NULL;
 
-	wr_lock(&cgpu->qlock);
+	if (unlikely(!cgpu))
+		return;
+
+	/* Use only a trylock in case we get into a deadlock with a queueing
+	 * function holding the read lock when we're called. */
+	if (wr_trylock(&cgpu->qlock))
+		return;
 	work = cgpu->unqueued_work;
 	cgpu->unqueued_work = NULL;
 	wr_unlock(&cgpu->qlock);