Rename "QEMU global mutex" to "BQL" in comments and docs

The term "QEMU global mutex" is identical to the more widely used Big
QEMU Lock ("BQL"). Update the code comments and documentation to use
"BQL" instead of "QEMU global mutex".

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Acked-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Paul Durrant <paul@xen.org>
Reviewed-by: Akihiko Odaki <akihiko.odaki@daynix.com>
Reviewed-by: Cédric Le Goater <clg@kaod.org>
Reviewed-by: Harsh Prateek Bora <harshpb@linux.ibm.com>
Message-id: 20240102153529.486531-6-stefanha@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

include/block/blockjob.h

@@ -54,7 +54,7 @@ typedef struct BlockJob {
 
     /**
      * Speed that was set with @block_job_set_speed.
-     * Always modified and read under QEMU global mutex (GLOBAL_STATE_CODE).
+     * Always modified and read under the BQL (GLOBAL_STATE_CODE).
      */
     int64_t speed;
 
@@ -66,7 +66,7 @@ typedef struct BlockJob {
 
     /**
      * Block other operations when block job is running.
-     * Always modified and read under QEMU global mutex (GLOBAL_STATE_CODE).
+     * Always modified and read under the BQL (GLOBAL_STATE_CODE).
      */
     Error *blocker;
 
@@ -89,7 +89,7 @@ typedef struct BlockJob {
 
     /**
      * BlockDriverStates that are involved in this block job.
-     * Always modified and read under QEMU global mutex (GLOBAL_STATE_CODE).
+     * Always modified and read under the BQL (GLOBAL_STATE_CODE).
      */
     GSList *nodes;
 } BlockJob;

include/io/task.h

@@ -149,7 +149,7 @@ typedef void (*QIOTaskWorker)(QIOTask *task,
  * lookups) to be easily run non-blocking. Reporting the
  * results in the main thread context means that the caller
  * typically does not need to be concerned about thread
- * safety wrt the QEMU global mutex.
+ * safety wrt the BQL.
  *
  * For example, the socket_listen() method will block the caller
  * while DNS lookups take place if given a name, instead of IP

include/qemu/coroutine-core.h

@@ -22,7 +22,7 @@
  * rather than callbacks, for operations that need to give up control while
  * waiting for events to complete.
  *
- * These functions are re-entrant and may be used outside the global mutex.
+ * These functions are re-entrant and may be used outside the BQL.
  *
  * Functions that execute in coroutine context cannot be called
  * directly from normal functions.  Use @coroutine_fn to mark such

include/qemu/coroutine.h

@@ -26,7 +26,7 @@
  * rather than callbacks, for operations that need to give up control while
  * waiting for events to complete.
  *
- * These functions are re-entrant and may be used outside the global mutex.
+ * These functions are re-entrant and may be used outside the BQL.
  *
  * Functions that execute in coroutine context cannot be called
  * directly from normal functions.  Use @coroutine_fn to mark such