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>

4 files changed, 15 insertions, 15 deletions

diff --git a/util/async.c b/util/async.c
index 460529057c..36a8e76ab0 100644
--- a/util/async.c
+++ b/util/async.c
@@ -727,7 +727,7 @@ AioContext *qemu_get_current_aio_context(void)
     if (ctx) {
         return ctx;
     }
-    if (qemu_mutex_iothread_locked()) {
+    if (bql_locked()) {
         /* Possibly in a vCPU thread.  */
         return qemu_get_aio_context();
     }
diff --git a/util/main-loop.c b/util/main-loop.c
index 63b4cda84a..a0386cfeb6 100644
--- a/util/main-loop.c
+++ b/util/main-loop.c
@@ -299,13 +299,13 @@ static int os_host_main_loop_wait(int64_t timeout)
 
     glib_pollfds_fill(&timeout);
 
-    qemu_mutex_unlock_iothread();
+    bql_unlock();
     replay_mutex_unlock();
 
     ret = qemu_poll_ns((GPollFD *)gpollfds->data, gpollfds->len, timeout);
 
     replay_mutex_lock();
-    qemu_mutex_lock_iothread();
+    bql_lock();
 
     glib_pollfds_poll();
 
@@ -514,7 +514,7 @@ static int os_host_main_loop_wait(int64_t timeout)
 
     poll_timeout_ns = qemu_soonest_timeout(poll_timeout_ns, timeout);
 
-    qemu_mutex_unlock_iothread();
+    bql_unlock();
 
     replay_mutex_unlock();
 
@@ -522,7 +522,7 @@ static int os_host_main_loop_wait(int64_t timeout)
 
     replay_mutex_lock();
 
-    qemu_mutex_lock_iothread();
+    bql_lock();
     if (g_poll_ret > 0) {
         for (i = 0; i < w->num; i++) {
             w->revents[i] = poll_fds[n_poll_fds + i].revents;
diff --git a/util/qsp.c b/util/qsp.c
index 2fe3764906..6b783e2e7f 100644
--- a/util/qsp.c
+++ b/util/qsp.c
@@ -124,7 +124,7 @@ static const char * const qsp_typenames[] = {
     [QSP_CONDVAR]   = "condvar",
 };
 
-QemuMutexLockFunc qemu_bql_mutex_lock_func = qemu_mutex_lock_impl;
+QemuMutexLockFunc bql_mutex_lock_func = qemu_mutex_lock_impl;
 QemuMutexLockFunc qemu_mutex_lock_func = qemu_mutex_lock_impl;
 QemuMutexTrylockFunc qemu_mutex_trylock_func = qemu_mutex_trylock_impl;
 QemuRecMutexLockFunc qemu_rec_mutex_lock_func = qemu_rec_mutex_lock_impl;
@@ -439,7 +439,7 @@ void qsp_enable(void)
 {
     qatomic_set(&qemu_mutex_lock_func, qsp_mutex_lock);
     qatomic_set(&qemu_mutex_trylock_func, qsp_mutex_trylock);
-    qatomic_set(&qemu_bql_mutex_lock_func, qsp_bql_mutex_lock);
+    qatomic_set(&bql_mutex_lock_func, qsp_bql_mutex_lock);
     qatomic_set(&qemu_rec_mutex_lock_func, qsp_rec_mutex_lock);
     qatomic_set(&qemu_rec_mutex_trylock_func, qsp_rec_mutex_trylock);
     qatomic_set(&qemu_cond_wait_func, qsp_cond_wait);
@@ -450,7 +450,7 @@ void qsp_disable(void)
 {
     qatomic_set(&qemu_mutex_lock_func, qemu_mutex_lock_impl);
     qatomic_set(&qemu_mutex_trylock_func, qemu_mutex_trylock_impl);
-    qatomic_set(&qemu_bql_mutex_lock_func, qemu_mutex_lock_impl);
+    qatomic_set(&bql_mutex_lock_func, qemu_mutex_lock_impl);
     qatomic_set(&qemu_rec_mutex_lock_func, qemu_rec_mutex_lock_impl);
     qatomic_set(&qemu_rec_mutex_trylock_func, qemu_rec_mutex_trylock_impl);
     qatomic_set(&qemu_cond_wait_func, qemu_cond_wait_impl);
diff --git a/util/rcu.c b/util/rcu.c
index e587bcc483..bb7f633b5c 100644
--- a/util/rcu.c
+++ b/util/rcu.c
@@ -283,24 +283,24 @@ static void *call_rcu_thread(void *opaque)
 
         qatomic_sub(&rcu_call_count, n);
         synchronize_rcu();
-        qemu_mutex_lock_iothread();
+        bql_lock();
         while (n > 0) {
             node = try_dequeue();
             while (!node) {
-                qemu_mutex_unlock_iothread();
+                bql_unlock();
                 qemu_event_reset(&rcu_call_ready_event);
                 node = try_dequeue();
                 if (!node) {
                     qemu_event_wait(&rcu_call_ready_event);
                     node = try_dequeue();
                 }
-                qemu_mutex_lock_iothread();
+                bql_lock();
             }
 
             n--;
             node->func(node);
         }
-        qemu_mutex_unlock_iothread();
+        bql_unlock();
     }
     abort();
 }
@@ -337,13 +337,13 @@ static void drain_rcu_callback(struct rcu_head *node)
 void drain_call_rcu(void)
 {
     struct rcu_drain rcu_drain;
-    bool locked = qemu_mutex_iothread_locked();
+    bool locked = bql_locked();
 
     memset(&rcu_drain, 0, sizeof(struct rcu_drain));
     qemu_event_init(&rcu_drain.drain_complete_event, false);
 
     if (locked) {
-        qemu_mutex_unlock_iothread();
+        bql_unlock();
     }
 
 
@@ -365,7 +365,7 @@ void drain_call_rcu(void)
     qatomic_dec(&in_drain_call_rcu);
 
     if (locked) {
-        qemu_mutex_lock_iothread();
+        bql_lock();
     }
 
 }