Use a portable boolean to tell us when ckdb is offline and change it under lock

src/stratifier.c

@@ -286,6 +286,8 @@ struct stratifier_data {
 	/* Serialises sends/receives to ckdb if possible */
 	pthread_mutex_t ckdb_lock;
 
+	bool ckdb_offline;
+
 	/* Variable length enonce1 always refers back to a u64 */
 	union {
 		uint64_t u64;
@@ -3326,9 +3328,33 @@ static void parse_ckdb_cmd(ckpool_t __maybe_unused *ckp, const char *cmd)
 	json_decref(val);
 }
 
+/* Test a value under lock and set it, returning the original value */
+static bool test_and_set(bool *val, pthread_mutex_t *lock)
+{
+	bool ret;
+
+	mutex_lock(lock);
+	ret = *val;
+	*val = true;
+	mutex_unlock(lock);
+
+	return ret;
+}
+
+static bool test_and_clear(bool *val, pthread_mutex_t *lock)
+{
+	bool ret;
+
+	mutex_lock(lock);
+	ret = *val;
+	*val = false;
+	mutex_unlock(lock);
+
+	return ret;
+}
+
 static void ckdbq_process(ckpool_t *ckp, char *msg)
 {
-	static bool failed = false;
 	sdata_t *sdata = ckp->data;
 	char *buf = NULL;
 
@@ -3338,18 +3364,15 @@ static void ckdbq_process(ckpool_t *ckp, char *msg)
 		mutex_unlock(&sdata->ckdb_lock);
 
 		if (unlikely(!buf)) {
-			if (!failed) {
-				failed = true;
+			if (!test_and_set(&sdata->ckdb_offline, &sdata->ckdb_lock))
 				LOGWARNING("Failed to talk to ckdb, queueing messages");
-			}
 			sleep(5);
 		}
 	}
 	free(msg);
-	if (failed) {
-		failed = false;
+	if (test_and_clear(&sdata->ckdb_offline, &sdata->ckdb_lock))
 		LOGWARNING("Successfully resumed talking to ckdb");
-	}
+
 	/* TODO: Process any requests from ckdb that are heartbeat responses
 	 * with specific requests. */
 	if (likely(buf)) {