2 files changed, 47 insertions, 4 deletions
diff --git a/include/block/block-common.h b/include/block/block-common.h
index 4168681..469300f 100644
--- a/include/block/block-common.h
+++ b/include/block/block-common.h
@@ -45,11 +45,14 @@
  * - co_wrapper_mixed_bdrv_rdlock are co_wrapper_mixed functions but
  *   automatically take and release the graph rdlock when creating a new
  *   coroutine.
+ *
+ * These functions should not be called from a coroutine_fn; instead,
+ * call the wrapped function directly.
  */
-#define co_wrapper
-#define co_wrapper_mixed
-#define co_wrapper_bdrv_rdlock
-#define co_wrapper_mixed_bdrv_rdlock
+#define co_wrapper                     no_coroutine_fn
+#define co_wrapper_mixed               no_coroutine_fn coroutine_mixed_fn
+#define co_wrapper_bdrv_rdlock         no_coroutine_fn
+#define co_wrapper_mixed_bdrv_rdlock   no_coroutine_fn coroutine_mixed_fn
 
 #include "block/blockjob.h"
 
diff --git a/include/qemu/osdep.h b/include/qemu/osdep.h
index d1be7bf..88c9fac 100644
--- a/include/qemu/osdep.h
+++ b/include/qemu/osdep.h
@@ -177,6 +177,46 @@ extern "C" {
 #define coroutine_fn
 #endif
 
+/**
+ * Mark a function that can suspend when executed in coroutine context,
+ * but can handle running in non-coroutine context too.
+ */
+#ifdef __clang__
+#define coroutine_mixed_fn __attribute__((__annotate__("coroutine_mixed_fn")))
+#else
+#define coroutine_mixed_fn
+#endif
+
+/**
+ * Mark a function that should not be called from a coroutine context.
+ * Usually there will be an analogous, coroutine_fn function that should
+ * be used instead.
+ *
+ * When the function is also marked as coroutine_mixed_fn, the function should
+ * only be called if the caller does not know whether it is in coroutine
+ * context.
+ *
+ * Functions that are only no_coroutine_fn, on the other hand, should not
+ * be called from within coroutines at all.  This for example includes
+ * functions that block.
+ *
+ * In the future it would be nice to enable compiler or static checker
+ * support for catching such errors.  This annotation is the first step
+ * towards this, and in the meantime it serves as documentation.
+ *
+ * For example:
+ *
+ *   static void no_coroutine_fn foo(void) {
+ *       ....
+ *   }
+ */
+#ifdef __clang__
+#define no_coroutine_fn __attribute__((__annotate__("no_coroutine_fn")))
+#else
+#define no_coroutine_fn
+#endif
+
+
 /*
  * For mingw, as of v6.0.0, the function implementing the assert macro is
  * not marked as noreturn, so the compiler cannot delete code following an