From 67c00d57c68dd4c1e48c5e85b9e9cb4218cbff6c Mon Sep 17 00:00:00 2001
From: Con Kolivas <kernel@kolivas.org>
Date: Wed, 4 Feb 2015 23:42:16 +1100
Subject: [PATCH] Fine grain the locking for read/write sections using the
 upgradeable variants in the stratifier where suitable

---
 src/stratifier.c | 38 ++++++++++++++++++++++++++++----------
 1 file changed, 28 insertions(+), 10 deletions(-)

diff --git a/src/stratifier.c b/src/stratifier.c
index cfc959db..6be91432 100644
--- a/src/stratifier.c
+++ b/src/stratifier.c
@@ -1160,15 +1160,19 @@ static stratum_instance_t *ref_instance_by_id(sdata_t *sdata, const int64_t id)
 {
 	stratum_instance_t *client;
 
-	ck_wlock(&sdata->instance_lock);
+	ck_ilock(&sdata->instance_lock);
 	client = __instance_by_id(sdata, id);
 	if (client) {
 		if (unlikely(client->dropped))
 			client = NULL;
-		else
+		else {
+			/* Upgrade to write lock to modify client refcount */
+			ck_ulock(&sdata->instance_lock);
 			__inc_instance_ref(client);
+			ck_dwilock(&sdata->instance_lock);
+		}
 	}
-	ck_wunlock(&sdata->instance_lock);
+	ck_uilock(&sdata->instance_lock);
 
 	return client;
 }
@@ -1292,7 +1296,7 @@ static uint64_t disconnected_sessionid_exists(sdata_t *sdata, const char *sessio
 	/* Number is in BE but we don't swap either of them */
 	hex2bin(&enonce1_64, sessionid, slen);
 
-	ck_wlock(&sdata->instance_lock);
+	ck_ilock(&sdata->instance_lock);
 	HASH_ITER(hh, sdata->stratum_instances, client, tmp) {
 		if (client->id == id)
 			continue;
@@ -1307,11 +1311,16 @@ static uint64_t disconnected_sessionid_exists(sdata_t *sdata, const char *sessio
 		/* Delete the entry once we are going to use it since there
 		 * will be a new instance with the enonce1_64 */
 		old_id = client->id;
+
+		/* Upgrade to write lock to disconnect */
+		ck_ulock(&sdata->instance_lock);
 		__del_disconnected(sdata, client);
+		ck_dwilock(&sdata->instance_lock);
+
 		ret = enonce1_64;
 	}
 out_unlock:
-	ck_wunlock(&sdata->instance_lock);
+	ck_uilock(&sdata->instance_lock);
 out:
 	if (ret)
 		LOGNOTICE("Reconnecting old instance %ld to instance %ld", old_id, id);
@@ -1406,8 +1415,10 @@ static void drop_client(sdata_t *sdata, const int64_t id)
 
 	LOGINFO("Stratifier asked to drop client %ld", id);
 
-	ck_wlock(&sdata->instance_lock);
+	ck_ilock(&sdata->instance_lock);
 	client = __instance_by_id(sdata, id);
+	/* Upgrade to write lock */
+	ck_ulock(&sdata->instance_lock);
 	if (client && !client->dropped) {
 		user = client->user_instance;
 		ckp = client->ckp;
@@ -2171,8 +2182,10 @@ static user_instance_t *generate_user(ckpool_t *ckp, stratum_instance_t *client,
 	if (unlikely(len > 127))
 		username[127] = '\0';
 
-	ck_wlock(&sdata->instance_lock);
+	ck_ilock(&sdata->instance_lock);
 	HASH_FIND_STR(sdata->user_instances, username, user);
+	/* Upgrade to write lock */
+	ck_ulock(&sdata->instance_lock);
 	if (!user) {
 		/* New user instance. Secondary user id will be NULL */
 		user = ckzalloc(sizeof(user_instance_t));
@@ -3451,8 +3464,10 @@ static void srecv_process(ckpool_t *ckp, char *buf)
 	json_object_clear(val);
 
 	/* Parse the message here */
-	ck_wlock(&sdata->instance_lock);
+	ck_ilock(&sdata->instance_lock);
 	client = __instance_by_id(sdata, msg->client_id);
+	/* Upgrade to write lock */
+	ck_ulock(&sdata->instance_lock);
 	/* If client_id instance doesn't exist yet, create one */
 	if (unlikely(!client)) {
 		if (likely(!__dropped_instance(sdata, msg->client_id))) {
@@ -3545,17 +3560,20 @@ static stratum_instance_t *preauth_ref_instance_by_id(sdata_t *sdata, const int6
 {
 	stratum_instance_t *client;
 
-	ck_wlock(&sdata->instance_lock);
+	ck_ilock(&sdata->instance_lock);
 	client = __instance_by_id(sdata, id);
 	if (client) {
 		if (client->dropped || client->authorising || client->authorised)
 			client = NULL;
 		else {
+			/* Upgrade to write lock to modify client data */
+			ck_ulock(&sdata->instance_lock);
 			__inc_instance_ref(client);
 			client->authorising = true;
+			ck_dwilock(&sdata->instance_lock);
 		}
 	}
-	ck_wunlock(&sdata->instance_lock);
+	ck_uilock(&sdata->instance_lock);
 
 	return client;
 }