Prevent data race between T1C and T2C

T2C uses the translated blocks (IRs) to establish the LLVM-IR. However,
the cache might be modified by the main thread while the background
thread is compiling.

Author: vacantron

src/emulate.c

@@ -832,11 +832,19 @@ static block_t *block_find_or_translate(riscv_t *rv)
 #else
     list_add(&next_blk->list, &rv->block_list);
 
+#if RV32_HAS(T2C)
+    pthread_mutex_lock(&rv->cache_lock);
+#endif
+
     /* insert the block into block cache */
     block_t *replaced_blk = cache_put(rv->block_cache, rv->PC, next_blk);
 
-    if (!replaced_blk)
+    if (!replaced_blk) {
+#if RV32_HAS(T2C)
+        pthread_mutex_unlock(&rv->cache_lock);
+#endif
         return next_blk;
+    }
 
     list_del_init(&replaced_blk->list);
 
@@ -872,6 +880,9 @@ static block_t *block_find_or_translate(riscv_t *rv)
     }
 
     mpool_free(rv->block_mp, replaced_blk);
+#if RV32_HAS(T2C)
+    pthread_mutex_unlock(&rv->cache_lock);
+#endif
 #endif
 
     assert(next_blk);

src/riscv.c

@@ -201,7 +201,9 @@ static void *t2c_runloop(void *arg)
             pthread_mutex_lock(&rv->wait_queue_lock);
             list_del_init(&entry->list);
             pthread_mutex_unlock(&rv->wait_queue_lock);
+            pthread_mutex_lock(&rv->cache_lock);
             t2c_compile(rv, entry->block);
+            pthread_mutex_unlock(&rv->cache_lock);
             free(entry);
         }
     }
@@ -324,6 +326,7 @@ riscv_t *rv_create(riscv_user_t rv_attr)
     rv->jit_cache = jit_cache_init();
     /* prepare wait queue. */
     pthread_mutex_init(&rv->wait_queue_lock, NULL);
+    pthread_mutex_init(&rv->cache_lock, NULL);
     INIT_LIST_HEAD(&rv->wait_queue);
     /* activate the background compilation thread. */
     pthread_create(&t2c_thread, NULL, t2c_runloop, rv);
@@ -422,6 +425,7 @@ void rv_delete(riscv_t *rv)
     rv->quit = true;
     pthread_join(t2c_thread, NULL);
     pthread_mutex_destroy(&rv->wait_queue_lock);
+    pthread_mutex_destroy(&rv->cache_lock);
     jit_cache_exit(rv->jit_cache);
 #endif
     jit_state_exit(rv->jit_state);

src/riscv_private.h

@@ -175,7 +175,7 @@ struct riscv_internal {
     struct list_head block_list; /**< list of all translated blocks */
 #if RV32_HAS(T2C)
     struct list_head wait_queue;
-    pthread_mutex_t wait_queue_lock;
+    pthread_mutex_t wait_queue_lock, cache_lock;
     volatile bool quit; /**< Determine the main thread is terminated or not */
 #endif
 #endif