store the next difficulty

miner.h

@@ -1338,6 +1338,7 @@ struct pool {
 	char bbversion[12];
 	char nbit[12];
 	char ntime[12];
+	double next_diff;
 	double sdiff;
 
 	struct timeval tv_lastwork;

util.c

@@ -2008,6 +2008,7 @@ static bool parse_notify(struct pool *pool, json_t *val)
 	snprintf(pool->nbit, 9, "%s", nbit);
 	snprintf(pool->ntime, 9, "%s", ntime);
 	pool->swork.clean = clean;
+	pool->sdiff = pool->next_diff;
 	alloc_len = pool->coinbase_len = cb1_len + pool->n1_len + pool->n2size + cb2_len;
 	pool->nonce2_offset = cb1_len + pool->n1_len;
 
@@ -2116,8 +2117,8 @@ static bool parse_diff(struct pool *pool, json_t *val)
 		return false;
 
 	cg_wlock(&pool->data_lock);
-	old_diff = pool->sdiff;
-	pool->sdiff = diff;
+	old_diff = pool->next_diff;
+	pool->next_diff = diff;
 	cg_wunlock(&pool->data_lock);
 
 	if (old_diff != diff) {
@@ -2915,7 +2916,7 @@ bool initiate_stratum(struct pool *pool)
 		if (!pool->stratum_url)
 			pool->stratum_url = pool->sockaddr_url;
 		pool->stratum_active = true;
-		pool->sdiff = 1;
+		pool->next_diff = pool->sdiff = 1;
 		if (opt_protocol) {
 			applog(LOG_DEBUG, "Pool %d confirmed mining.subscribe with extranonce1 %s extran2size %d",
 			       pool->pool_no, pool->nonce1, pool->n2size);