Modules TSC: Basic TS context creeation and handling.

src/module.c

@@ -95,10 +95,15 @@ typedef struct RedisModulePoolAllocBlock {
  *
  * Note that not all the context structure is always filled with actual values
  * but only the fields needed in a given context. */
+
+struct RedisModuleBlockedClient;
+
 struct RedisModuleCtx {
     void *getapifuncptr;            /* NOTE: Must be the first field. */
     struct RedisModule *module;     /* Module reference. */
     client *client;                 /* Client calling a command. */
+    struct RedisModuleBlockedClient *blocked_client; /* Blocked client for
+                                                        thread safe context. */
     struct AutoMemEntry *amqueue;   /* Auto memory queue of objects to free. */
     int amqueue_len;                /* Number of slots in amqueue. */
     int amqueue_used;               /* Number of used slots in amqueue. */
@@ -115,12 +120,13 @@ struct RedisModuleCtx {
 };
 typedef struct RedisModuleCtx RedisModuleCtx;
 
-#define REDISMODULE_CTX_INIT {(void*)(unsigned long)&RM_GetApi, NULL, NULL, NULL, 0, 0, 0, NULL, 0, NULL, NULL, 0, NULL}
+#define REDISMODULE_CTX_INIT {(void*)(unsigned long)&RM_GetApi, NULL, NULL, NULL, NULL, 0, 0, 0, NULL, 0, NULL, NULL, 0, NULL}
 #define REDISMODULE_CTX_MULTI_EMITTED (1<<0)
 #define REDISMODULE_CTX_AUTO_MEMORY (1<<1)
 #define REDISMODULE_CTX_KEYS_POS_REQUEST (1<<2)
 #define REDISMODULE_CTX_BLOCKED_REPLY (1<<3)
 #define REDISMODULE_CTX_BLOCKED_TIMEOUT (1<<4)
+#define REDISMODULE_CTX_THREAD_SAFE (1<<5)
 
 /* This represents a Redis key opened with RM_OpenKey(). */
 struct RedisModuleKey {
@@ -198,6 +204,8 @@ typedef struct RedisModuleBlockedClient {
     void *privdata;     /* Module private data that may be used by the reply
                            or timeout callback. It is set via the
                            RedisModule_UnblockClient() API. */
+    client *reply_client;           /* Fake client used to accumulate replies
+                                       in thread safe contexts. */
 } RedisModuleBlockedClient;
 
 static pthread_mutex_t moduleUnblockedClientsMutex = PTHREAD_MUTEX_INITIALIZER;
@@ -3165,6 +3173,7 @@ RedisModuleBlockedClient *RM_BlockClient(RedisModuleCtx *ctx, RedisModuleCmdFunc
     bc->timeout_callback = timeout_callback;
     bc->free_privdata = free_privdata;
     bc->privdata = NULL;
+    bc->reply_client = NULL;
     c->bpop.timeout = timeout_ms ? (mstime()+timeout_ms) : 0;
 
     blockClient(c,BLOCKED_MODULE);
@@ -3300,6 +3309,56 @@ void moduleCooperativeMultiTaskingCycle(void) {
     pthread_mutex_lock(&moduleGIL);
 }
 
+/* Return a context which can be used inside threads to make Redis context
+ * calls with certain modules APIs. If 'bc' is not NULL then the module will
+ * be bound to a blocked client, and it will be possible to use the
+ * `RedisModule_Reply*` family of functions to accumulate a reply for when the
+ * client will be unblocked. Otherwise the thread safe context will be
+ * detached by a specific client.
+ *
+ * To call non-reply APIs, the thread safe context must be prepared with:
+ *
+ *  RedisModule_ThreadSafeCallStart(ctx);
+ *  ... make your call here ...
+ *  RedisModule_ThreadSafeCallStop(ctx);
+ *
+ * This is not needed when using `RedisModule_Reply*` functions, assuming
+ * that a blocked client was used when the context was created, otherwise
+ * no RedisModule_Reply* call should be made at all.
+ */
+RedisModuleCtx *RM_GetThreadSafeContext(RedisModuleBlockedClient *bc) {
+    RedisModuleCtx *ctx = zmalloc(sizeof(*ctx));
+    RedisModuleCtx empty = REDISMODULE_CTX_INIT;
+    memcpy(ctx,&empty,sizeof(empty));
+    if (bc) {
+        ctx->blocked_client = bc;
+        if (bc->reply_client == NULL)
+            bc->reply_client = createClient(-1);
+    }
+    ctx->flags |= REDISMODULE_CTX_THREAD_SAFE;
+    return ctx;
+}
+
+/* Release a thread safe context. */
+void RM_FreeThreadSafeContext(RedisModuleCtx *ctx) {
+    moduleFreeContext(ctx);
+    zfree(ctx);
+}
+
+/* Acquire the server lock before executing a thread safe API call.
+ * This is not needed for `RedisModule_Reply*` calls when there is
+ * a blocked client connected to the thread safe context. */
+void RM_ThreadSafeContextLock(RedisModuleCtx *ctx) {
+    DICT_NOTUSED(ctx);
+    pthread_mutex_lock(&moduleGIL);
+}
+
+/* Release the server lock after a thread safe API call was executed. */
+void RM_ThreadSafeContextUnlock(RedisModuleCtx *ctx) {
+    DICT_NOTUSED(ctx);
+    pthread_mutex_unlock(&moduleGIL);
+}
+
 /* --------------------------------------------------------------------------
  * Modules API internals
  * -------------------------------------------------------------------------- */