diff --git a/crypto/drbg.c b/crypto/drbg.c
index 74f7c1e..d34926b 100644
--- a/crypto/drbg.c
+++ b/crypto/drbg.c
@@ -1181,7 +1181,6 @@ static inline int drbg_alloc_state(struct drbg_state *drbg)
 		if (!drbg->scratchpad)
 			goto err;
 	}
-	spin_lock_init(&drbg->drbg_lock);
 	return 0;
 
 err:
@@ -1189,79 +1188,6 @@ err:
 	return ret;
 }
 
-/*
- * Strategy to avoid holding long term locks: generate a shadow copy of DRBG
- * and perform all operations on this shadow copy. After finishing, restore
- * the updated state of the shadow copy into original drbg state. This way,
- * only the read and write operations of the original drbg state must be
- * locked
- */
-static inline void drbg_copy_drbg(struct drbg_state *src,
-				  struct drbg_state *dst)
-{
-	if (!src || !dst)
-		return;
-	memcpy(dst->V, src->V, drbg_statelen(src));
-	memcpy(dst->C, src->C, drbg_statelen(src));
-	dst->reseed_ctr = src->reseed_ctr;
-	dst->seeded = src->seeded;
-	dst->pr = src->pr;
-#ifdef CONFIG_CRYPTO_FIPS
-	dst->fips_primed = src->fips_primed;
-	memcpy(dst->prev, src->prev, drbg_blocklen(src));
-#endif
-	/*
-	 * Not copied:
-	 * scratchpad is initialized drbg_alloc_state;
-	 * priv_data is initialized with call to crypto_init;
-	 * d_ops and core are set outside, as these parameters are const;
-	 * test_data is set outside to prevent it being copied back.
-	 */
-}
-
-static int drbg_make_shadow(struct drbg_state *drbg, struct drbg_state **shadow)
-{
-	int ret = -ENOMEM;
-	struct drbg_state *tmp = NULL;
-
-	tmp = kzalloc(sizeof(struct drbg_state), GFP_KERNEL);
-	if (!tmp)
-		return -ENOMEM;
-
-	/* read-only data as they are defined as const, no lock needed */
-	tmp->core = drbg->core;
-	tmp->d_ops = drbg->d_ops;
-
-	ret = drbg_alloc_state(tmp);
-	if (ret)
-		goto err;
-
-	spin_lock_bh(&drbg->drbg_lock);
-	drbg_copy_drbg(drbg, tmp);
-	/* only make a link to the test buffer, as we only read that data */
-	tmp->test_data = drbg->test_data;
-	spin_unlock_bh(&drbg->drbg_lock);
-	*shadow = tmp;
-	return 0;
-
-err:
-	kzfree(tmp);
-	return ret;
-}
-
-static void drbg_restore_shadow(struct drbg_state *drbg,
-				struct drbg_state **shadow)
-{
-	struct drbg_state *tmp = *shadow;
-
-	spin_lock_bh(&drbg->drbg_lock);
-	drbg_copy_drbg(tmp, drbg);
-	spin_unlock_bh(&drbg->drbg_lock);
-	drbg_dealloc_state(tmp);
-	kzfree(tmp);
-	*shadow = NULL;
-}
-
 /*************************************************************************
  * DRBG interface functions
  *************************************************************************/
@@ -1287,13 +1213,7 @@ static int drbg_generate(struct drbg_state *drbg,
 			 struct drbg_string *addtl)
 {
 	int len = 0;
-	struct drbg_state *shadow = NULL;
 	LIST_HEAD(addtllist);
-	struct drbg_string timestamp;
-	union {
-		cycles_t cycles;
-		unsigned char char_cycles[sizeof(cycles_t)];
-	} now;
 
 	if (0 == buflen || !buf) {
 		pr_devel("DRBG: no output buffer provided\n");
@@ -1304,15 +1224,9 @@ static int drbg_generate(struct drbg_state *drbg,
 		return -EINVAL;
 	}
 
-	len = drbg_make_shadow(drbg, &shadow);
-	if (len) {
-		pr_devel("DRBG: shadow copy cannot be generated\n");
-		return len;
-	}
-
 	/* 9.3.1 step 2 */
 	len = -EINVAL;
-	if (buflen > (drbg_max_request_bytes(shadow))) {
+	if (buflen > (drbg_max_request_bytes(drbg))) {
 		pr_devel("DRBG: requested random numbers too large %u\n",
 			 buflen);
 		goto err;
@@ -1321,7 +1235,7 @@ static int drbg_generate(struct drbg_state *drbg,
 	/* 9.3.1 step 3 is implicit with the chosen DRBG */
 
 	/* 9.3.1 step 4 */
-	if (addtl && addtl->len > (drbg_max_addtl(shadow))) {
+	if (addtl && addtl->len > (drbg_max_addtl(drbg))) {
 		pr_devel("DRBG: additional information string too long %zu\n",
 			 addtl->len);
 		goto err;
@@ -1332,46 +1246,34 @@ static int drbg_generate(struct drbg_state *drbg,
 	 * 9.3.1 step 6 and 9 supplemented by 9.3.2 step c is implemented
 	 * here. The spec is a bit convoluted here, we make it simpler.
 	 */
-	if ((drbg_max_requests(shadow)) < shadow->reseed_ctr)
-		shadow->seeded = false;
+	if ((drbg_max_requests(drbg)) < drbg->reseed_ctr)
+		drbg->seeded = false;
 
 	/* allocate cipher handle */
-	len = shadow->d_ops->crypto_init(shadow);
+	len = drbg->d_ops->crypto_init(drbg);
 	if (len)
 		goto err;
 
-	if (shadow->pr || !shadow->seeded) {
+	if (drbg->pr || !drbg->seeded) {
 		pr_devel("DRBG: reseeding before generation (prediction "
 			 "resistance: %s, state %s)\n",
 			 drbg->pr ? "true" : "false",
 			 drbg->seeded ? "seeded" : "unseeded");
 		/* 9.3.1 steps 7.1 through 7.3 */
-		len = drbg_seed(shadow, addtl, true);
+		len = drbg_seed(drbg, addtl, true);
 		if (len)
 			goto err;
 		/* 9.3.1 step 7.4 */
 		addtl = NULL;
 	}
 
-	/*
-	 * Mix the time stamp into the DRBG state if the DRBG is not in
-	 * test mode. If there are two callers invoking the DRBG at the same
-	 * time, i.e. before the first caller merges its shadow state back,
-	 * both callers would obtain the same random number stream without
-	 * changing the state here.
-	 */
-	if (!drbg->test_data) {
-		now.cycles = random_get_entropy();
-		drbg_string_fill(&timestamp, now.char_cycles, sizeof(cycles_t));
-		list_add_tail(&timestamp.list, &addtllist);
-	}
 	if (addtl && 0 < addtl->len)
 		list_add_tail(&addtl->list, &addtllist);
 	/* 9.3.1 step 8 and 10 */
-	len = shadow->d_ops->generate(shadow, buf, buflen, &addtllist);
+	len = drbg->d_ops->generate(drbg, buf, buflen, &addtllist);
 
 	/* 10.1.1.4 step 6, 10.1.2.5 step 7, 10.2.1.5.2 step 7 */
-	shadow->reseed_ctr++;
+	drbg->reseed_ctr++;
 	if (0 >= len)
 		goto err;
 
@@ -1391,7 +1293,7 @@ static int drbg_generate(struct drbg_state *drbg,
 	 * case somebody has a need to implement the test of 11.3.3.
 	 */
 #if 0
-	if (shadow->reseed_ctr && !(shadow->reseed_ctr % 4096)) {
+	if (drbg->reseed_ctr && !(drbg->reseed_ctr % 4096)) {
 		int err = 0;
 		pr_devel("DRBG: start to perform self test\n");
 		if (drbg->core->flags & DRBG_HMAC)
@@ -1410,8 +1312,6 @@ static int drbg_generate(struct drbg_state *drbg,
 			 * are returned when reusing this DRBG cipher handle
 			 */
 			drbg_uninstantiate(drbg);
-			drbg_dealloc_state(shadow);
-			kzfree(shadow);
 			return 0;
 		} else {
 			pr_devel("DRBG: self test successful\n");
@@ -1425,8 +1325,7 @@ static int drbg_generate(struct drbg_state *drbg,
 	 */
 	len = 0;
 err:
-	shadow->d_ops->crypto_fini(shadow);
-	drbg_restore_shadow(drbg, &shadow);
+	drbg->d_ops->crypto_fini(drbg);
 	return len;
 }
 
@@ -1449,7 +1348,9 @@ static int drbg_generate_long(struct drbg_state *drbg,
 		unsigned int chunk = 0;
 		slice = ((buflen - len) / drbg_max_request_bytes(drbg));
 		chunk = slice ? drbg_max_request_bytes(drbg) : (buflen - len);
+		mutex_lock(&drbg->drbg_mutex);
 		tmplen = drbg_generate(drbg, buf + len, chunk, addtl);
+		mutex_unlock(&drbg->drbg_mutex);
 		if (0 > tmplen)
 			return tmplen;
 		len += tmplen;
@@ -1477,10 +1378,11 @@ static int drbg_generate_long(struct drbg_state *drbg,
 static int drbg_instantiate(struct drbg_state *drbg, struct drbg_string *pers,
 			    int coreref, bool pr)
 {
-	int ret = -ENOMEM;
+	int ret = -EOPNOTSUPP;
 
 	pr_devel("DRBG: Initializing DRBG core %d with prediction resistance "
 		 "%s\n", coreref, pr ? "enabled" : "disabled");
+	mutex_lock(&drbg->drbg_mutex);
 	drbg->core = &drbg_cores[coreref];
 	drbg->pr = pr;
 	drbg->seeded = false;
@@ -1501,7 +1403,7 @@ static int drbg_instantiate(struct drbg_state *drbg, struct drbg_string *pers,
 		break;
 #endif /* CONFIG_CRYPTO_DRBG_CTR */
 	default:
-		return -EOPNOTSUPP;
+		goto unlock;
 	}
 
 	/* 9.1 step 1 is implicit with the selected DRBG type */
@@ -1516,7 +1418,7 @@ static int drbg_instantiate(struct drbg_state *drbg, struct drbg_string *pers,
 
 	ret = drbg_alloc_state(drbg);
 	if (ret)
-		return ret;
+		goto unlock;
 
 	ret = -EFAULT;
 	if (drbg->d_ops->crypto_init(drbg))
@@ -1526,10 +1428,13 @@ static int drbg_instantiate(struct drbg_state *drbg, struct drbg_string *pers,
 	if (ret)
 		goto err;
 
+	mutex_unlock(&drbg->drbg_mutex);
 	return 0;
 
 err:
 	drbg_dealloc_state(drbg);
+unlock:
+	mutex_unlock(&drbg->drbg_mutex);
 	return ret;
 }
 
@@ -1544,10 +1449,10 @@ err:
  */
 static int drbg_uninstantiate(struct drbg_state *drbg)
 {
-	spin_lock_bh(&drbg->drbg_lock);
+	mutex_lock(&drbg->drbg_mutex);
 	drbg_dealloc_state(drbg);
 	/* no scrubbing of test_data -- this shall survive an uninstantiate */
-	spin_unlock_bh(&drbg->drbg_lock);
+	mutex_unlock(&drbg->drbg_mutex);
 	return 0;
 }
 
@@ -1562,9 +1467,9 @@ static inline void drbg_set_testdata(struct drbg_state *drbg,
 {
 	if (!test_data || !test_data->testentropy)
 		return;
-	spin_lock_bh(&drbg->drbg_lock);
+	mutex_lock(&drbg->drbg_mutex);;
 	drbg->test_data = test_data;
-	spin_unlock_bh(&drbg->drbg_lock);
+	mutex_unlock(&drbg->drbg_mutex);
 }
 
 /***************************************************************
@@ -1717,6 +1622,7 @@ static int drbg_kcapi_init(struct crypto_tfm *tfm)
 	bool pr = false;
 	int coreref = 0;
 
+	mutex_init(&drbg->drbg_mutex);
 	drbg_convert_tfm_core(crypto_tfm_alg_driver_name(tfm), &coreref, &pr);
 	/*
 	 * when personalization string is needed, the caller must call reset
diff --git a/include/crypto/drbg.h b/include/crypto/drbg.h
index 5186f75..a43a7ed 100644
--- a/include/crypto/drbg.h
+++ b/include/crypto/drbg.h
@@ -49,7 +49,7 @@
 #include <crypto/internal/rng.h>
 #include <crypto/rng.h>
 #include <linux/fips.h>
-#include <linux/spinlock.h>
+#include <linux/mutex.h>
 #include <linux/list.h>
 
 /*
@@ -104,7 +104,7 @@ struct drbg_test_data {
 };
 
 struct drbg_state {
-	spinlock_t drbg_lock;	/* lock around DRBG */
+	struct mutex drbg_mutex;	/* lock around DRBG */
 	unsigned char *V;	/* internal state 10.1.1.1 1a) */
 	/* hash: static value 10.1.1.1 1b) hmac / ctr: key */
 	unsigned char *C;
