hwrng: core - Use struct completion for cleanup_done

There is no point in doing a manual completion for cleanup_done
when struct completion fits in perfectly.
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

drivers/char/hw_random/core.c

@@ -60,7 +60,6 @@ static DEFINE_MUTEX(rng_mutex);
 static DEFINE_MUTEX(reading_mutex);
 static int data_avail;
 static u8 *rng_buffer, *rng_fillbuf;
-static DECLARE_WAIT_QUEUE_HEAD(rng_done);
 static unsigned short current_quality;
 static unsigned short default_quality; /* = 0; default to "off" */
 
@@ -100,10 +99,7 @@ static inline void cleanup_rng(struct kref *kref)
 	if (rng->cleanup)
 		rng->cleanup(rng);
 
-	/* cleanup_done should be updated after cleanup finishes */
-	smp_wmb();
-	rng->cleanup_done = true;
-	wake_up_all(&rng_done);
+	complete(&rng->cleanup_done);
 }
 
 static void set_current_rng(struct hwrng *rng)
@@ -498,7 +494,7 @@ int hwrng_register(struct hwrng *rng)
 		add_early_randomness(rng);
 	}
 
-	rng->cleanup_done = false;
+	init_completion(&rng->cleanup_done);
 
 out_unlock:
 	mutex_unlock(&rng_mutex);
@@ -532,9 +528,7 @@ void hwrng_unregister(struct hwrng *rng)
 	} else
 		mutex_unlock(&rng_mutex);
 
-	/* Just in case rng is reading right now, wait. */
-	wait_event(rng_done, rng->cleanup_done &&
-		   atomic_read(&rng->ref.refcount) == 0);
+	wait_for_completion(&rng->cleanup_done);
 }
 EXPORT_SYMBOL_GPL(hwrng_unregister);
 

include/linux/hw_random.h

@@ -12,6 +12,7 @@
 #ifndef LINUX_HWRANDOM_H_
 #define LINUX_HWRANDOM_H_
 
+#include <linux/completion.h>
 #include <linux/types.h>
 #include <linux/list.h>
 #include <linux/kref.h>
@@ -46,7 +47,7 @@ struct hwrng {
 	/* internal. */
 	struct list_head list;
 	struct kref ref;
-	bool cleanup_done;
+	struct completion cleanup_done;
 };
 
 /** Register a new Hardware Random Number Generator driver. */