From: Amos Kong <akong@redhat.com>
Date: Mon, 8 Dec 2014 08:50:36 +0000 (+0800)
Subject: hwrng: move some code out mutex_lock for avoiding underlying deadlock
X-Git-Url: http://drtracing.org/?a=commitdiff_plain;h=1dacb395d68a14825ee48c0843335e3181aea675;p=deliverable%2Flinux.git

hwrng: move some code out mutex_lock for avoiding underlying deadlock

In next patch, we use reference counting for each struct hwrng,
changing reference count also needs to take mutex_lock. Before
releasing the lock, if we try to stop a kthread that waits to
take the lock to reduce the referencing count, deadlock will
occur.

Signed-off-by: Amos Kong <akong@redhat.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
---

diff --git a/drivers/char/hw_random/core.c b/drivers/char/hw_random/core.c
index 2dd3144d69b1..b4c0e873d362 100644
--- a/drivers/char/hw_random/core.c
+++ b/drivers/char/hw_random/core.c
@@ -470,12 +470,12 @@ void hwrng_unregister(struct hwrng *rng)
 		}
 	}
 	if (list_empty(&rng_list)) {
+		mutex_unlock(&rng_mutex);
 		unregister_miscdev();
 		if (hwrng_fill)
 			kthread_stop(hwrng_fill);
-	}
-
-	mutex_unlock(&rng_mutex);
+	} else
+		mutex_unlock(&rng_mutex);
 }
 EXPORT_SYMBOL_GPL(hwrng_unregister);