system/cpus: rename qemu_mutex_lock_iothread() to bql_lock()

The Big QEMU Lock (BQL) has many names and they are confusing. The
actual QemuMutex variable is called qemu_global_mutex but it's commonly
referred to as the BQL in discussions and some code comments. The
locking APIs, however, are called qemu_mutex_lock_iothread() and
qemu_mutex_unlock_iothread().

The "iothread" name is historic and comes from when the main thread was
split into into KVM vcpu threads and the "iothread" (now called the main
loop thread). I have contributed to the confusion myself by introducing
a separate --object iothread, a separate concept unrelated to the BQL.

The "iothread" name is no longer appropriate for the BQL. Rename the
locking APIs to:
- void bql_lock(void)
- void bql_unlock(void)
- bool bql_locked(void)

There are more APIs with "iothread" in their names. Subsequent patches
will rename them. There are also comments and documentation that will be
updated in later patches.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Paul Durrant <paul@xen.org>
Acked-by: Fabiano Rosas <farosas@suse.de>
Acked-by: David Woodhouse <dwmw@amazon.co.uk>
Reviewed-by: Cédric Le Goater <clg@kaod.org>
Acked-by: Peter Xu <peterx@redhat.com>
Acked-by: Eric Farman <farman@linux.ibm.com>
Reviewed-by: Harsh Prateek Bora <harshpb@linux.ibm.com>
Acked-by: Hyman Huang <yong.huang@smartx.com>
Reviewed-by: Akihiko Odaki <akihiko.odaki@daynix.com>
Message-id: 20240102153529.486531-2-stefanha@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

1 files changed, 6 insertions, 6 deletions

diff --git a/migration/ram.c b/migration/ram.c
index 8c7886ab79..08dc7e2909 100644
--- a/migration/ram.c
+++ b/migration/ram.c
@@ -2984,9 +2984,9 @@ static int ram_save_setup(QEMUFile *f, void *opaque)
     migration_ops = g_malloc0(sizeof(MigrationOps));
     migration_ops->ram_save_target_page = ram_save_target_page_legacy;
 
-    qemu_mutex_unlock_iothread();
+    bql_unlock();
     ret = multifd_send_sync_main(f);
-    qemu_mutex_lock_iothread();
+    bql_lock();
     if (ret < 0) {
         return ret;
     }
@@ -3221,11 +3221,11 @@ static void ram_state_pending_exact(void *opaque, uint64_t *must_precopy,
     uint64_t remaining_size = rs->migration_dirty_pages * TARGET_PAGE_SIZE;
 
     if (!migration_in_postcopy() && remaining_size < s->threshold_size) {
-        qemu_mutex_lock_iothread();
+        bql_lock();
         WITH_RCU_READ_LOCK_GUARD() {
             migration_bitmap_sync_precopy(rs, false);
         }
-        qemu_mutex_unlock_iothread();
+        bql_unlock();
         remaining_size = rs->migration_dirty_pages * TARGET_PAGE_SIZE;
     }
 
@@ -3453,7 +3453,7 @@ void colo_incoming_start_dirty_log(void)
 {
     RAMBlock *block = NULL;
     /* For memory_global_dirty_log_start below. */
-    qemu_mutex_lock_iothread();
+    bql_lock();
     qemu_mutex_lock_ramlist();
 
     memory_global_dirty_log_sync(false);
@@ -3467,7 +3467,7 @@ void colo_incoming_start_dirty_log(void)
     }
     ram_state->migration_dirty_pages = 0;
     qemu_mutex_unlock_ramlist();
-    qemu_mutex_unlock_iothread();
+    bql_unlock();
 }
 
 /* It is need to hold the global lock to call this helper */