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>

2 files changed, 11 insertions, 11 deletions

diff --git a/hw/remote/mpqemu-link.c b/hw/remote/mpqemu-link.c
index 9bd98e8219..d04ac93621 100644
--- a/hw/remote/mpqemu-link.c
+++ b/hw/remote/mpqemu-link.c
@@ -33,7 +33,7 @@
  */
 bool mpqemu_msg_send(MPQemuMsg *msg, QIOChannel *ioc, Error **errp)
 {
-    bool iolock = qemu_mutex_iothread_locked();
+    bool drop_bql = bql_locked();
     bool iothread = qemu_in_iothread();
     struct iovec send[2] = {};
     int *fds = NULL;
@@ -63,8 +63,8 @@ bool mpqemu_msg_send(MPQemuMsg *msg, QIOChannel *ioc, Error **errp)
      * for IOThread case.
      * Also skip lock handling while in a co-routine in the main context.
      */
-    if (iolock && !iothread && !qemu_in_coroutine()) {
-        qemu_mutex_unlock_iothread();
+    if (drop_bql && !iothread && !qemu_in_coroutine()) {
+        bql_unlock();
     }
 
     if (!qio_channel_writev_full_all(ioc, send, G_N_ELEMENTS(send),
@@ -74,9 +74,9 @@ bool mpqemu_msg_send(MPQemuMsg *msg, QIOChannel *ioc, Error **errp)
         trace_mpqemu_send_io_error(msg->cmd, msg->size, nfds);
     }
 
-    if (iolock && !iothread && !qemu_in_coroutine()) {
+    if (drop_bql && !iothread && !qemu_in_coroutine()) {
         /* See above comment why skip locking here. */
-        qemu_mutex_lock_iothread();
+        bql_lock();
     }
 
     return ret;
@@ -96,7 +96,7 @@ static ssize_t mpqemu_read(QIOChannel *ioc, void *buf, size_t len, int **fds,
                            size_t *nfds, Error **errp)
 {
     struct iovec iov = { .iov_base = buf, .iov_len = len };
-    bool iolock = qemu_mutex_iothread_locked();
+    bool drop_bql = bql_locked();
     bool iothread = qemu_in_iothread();
     int ret = -1;
 
@@ -106,14 +106,14 @@ static ssize_t mpqemu_read(QIOChannel *ioc, void *buf, size_t len, int **fds,
      */
     assert(qemu_in_coroutine() || !iothread);
 
-    if (iolock && !iothread && !qemu_in_coroutine()) {
-        qemu_mutex_unlock_iothread();
+    if (drop_bql && !iothread && !qemu_in_coroutine()) {
+        bql_unlock();
     }
 
     ret = qio_channel_readv_full_all_eof(ioc, &iov, 1, fds, nfds, errp);
 
-    if (iolock && !iothread && !qemu_in_coroutine()) {
-        qemu_mutex_lock_iothread();
+    if (drop_bql && !iothread && !qemu_in_coroutine()) {
+        bql_lock();
     }
 
     return (ret <= 0) ? ret : iov.iov_len;
diff --git a/hw/remote/vfio-user-obj.c b/hw/remote/vfio-user-obj.c
index 8b10c32a3c..d9b879e056 100644
--- a/hw/remote/vfio-user-obj.c
+++ b/hw/remote/vfio-user-obj.c
@@ -400,7 +400,7 @@ static int vfu_object_mr_rw(MemoryRegion *mr, uint8_t *buf, hwaddr offset,
         }
 
         if (release_lock) {
-            qemu_mutex_unlock_iothread();
+            bql_unlock();
             release_lock = false;
         }