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 2dd3144d69b1c626652816c01d928f6d928442b1..b4c0e873d36245c07b6b8ecb1f102e7ab2e411b7 100644 (file)
--- 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);