store the next difficulty

miner.h

@@ -1306,6 +1306,7 @@ struct pool {
 	unsigned char *coinbase;
 	size_t nonce2_offset;
 	unsigned char header_bin[128];
+	double next_diff;
 	int merkle_offset;
 
 	struct timeval tv_lastwork;

util.c

@@ -1550,6 +1550,7 @@ static bool parse_notify(struct pool *pool, json_t *val)
 	pool->swork.nbit = nbit;
 	pool->swork.ntime = ntime;
 	pool->swork.clean = clean;
+	pool->swork.diff = pool->next_diff;
 	alloc_len = pool->swork.cb_len = cb1_len + pool->n1_len + pool->n2size + cb2_len;
 	pool->nonce2_offset = cb1_len + pool->n1_len;
 
@@ -1647,8 +1648,8 @@ static bool parse_diff(struct pool *pool, json_t *val)
 		return false;
 
 	cg_wlock(&pool->data_lock);
-	old_diff = pool->swork.diff;
-	pool->swork.diff = diff;
+	old_diff = pool->next_diff;
+	pool->next_diff = diff;
 	cg_wunlock(&pool->data_lock);
 
 	if (old_diff != diff) {
@@ -2531,7 +2532,7 @@ out:
 		if (!pool->stratum_url)
 			pool->stratum_url = pool->sockaddr_url;
 		pool->stratum_active = true;
-		pool->swork.diff = 1;
+		pool->next_diff = pool->swork.diff = 1;
 		if (opt_protocol) {
 			applog(LOG_DEBUG, "%s confirmed mining.subscribe with extranonce1 %s extran2size %d",
 			       get_pool_name(pool), pool->nonce1, pool->n2size);