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, 13 insertions, 13 deletions

diff --git a/accel/kvm/kvm-accel-ops.c b/accel/kvm/kvm-accel-ops.c
index 6195150a0b..45ff06e953 100644
--- a/accel/kvm/kvm-accel-ops.c
+++ b/accel/kvm/kvm-accel-ops.c
@@ -33,7 +33,7 @@ static void *kvm_vcpu_thread_fn(void *arg)
 
     rcu_register_thread();
 
-    qemu_mutex_lock_iothread();
+    bql_lock();
     qemu_thread_get_self(cpu->thread);
     cpu->thread_id = qemu_get_thread_id();
     cpu->neg.can_do_io = true;
@@ -58,7 +58,7 @@ static void *kvm_vcpu_thread_fn(void *arg)
 
     kvm_destroy_vcpu(cpu);
     cpu_thread_signal_destroyed(cpu);
-    qemu_mutex_unlock_iothread();
+    bql_unlock();
     rcu_unregister_thread();
     return NULL;
 }
diff --git a/accel/kvm/kvm-all.c b/accel/kvm/kvm-all.c
index eb17773f0b..bbc60146d1 100644
--- a/accel/kvm/kvm-all.c
+++ b/accel/kvm/kvm-all.c
@@ -806,7 +806,7 @@ static void kvm_dirty_ring_flush(void)
      * should always be with BQL held, serialization is guaranteed.
      * However, let's be sure of it.
      */
-    assert(qemu_mutex_iothread_locked());
+    assert(bql_locked());
     /*
      * First make sure to flush the hardware buffers by kicking all
      * vcpus out in a synchronous way.
@@ -1391,9 +1391,9 @@ static void *kvm_dirty_ring_reaper_thread(void *data)
         trace_kvm_dirty_ring_reaper("wakeup");
         r->reaper_state = KVM_DIRTY_RING_REAPER_REAPING;
 
-        qemu_mutex_lock_iothread();
+        bql_lock();
         kvm_dirty_ring_reap(s, NULL);
-        qemu_mutex_unlock_iothread();
+        bql_unlock();
 
         r->reaper_iteration++;
     }
@@ -2817,7 +2817,7 @@ int kvm_cpu_exec(CPUState *cpu)
         return EXCP_HLT;
     }
 
-    qemu_mutex_unlock_iothread();
+    bql_unlock();
     cpu_exec_start(cpu);
 
     do {
@@ -2857,11 +2857,11 @@ int kvm_cpu_exec(CPUState *cpu)
 
 #ifdef KVM_HAVE_MCE_INJECTION
         if (unlikely(have_sigbus_pending)) {
-            qemu_mutex_lock_iothread();
+            bql_lock();
             kvm_arch_on_sigbus_vcpu(cpu, pending_sigbus_code,
                                     pending_sigbus_addr);
             have_sigbus_pending = false;
-            qemu_mutex_unlock_iothread();
+            bql_unlock();
         }
 #endif
 
@@ -2927,7 +2927,7 @@ int kvm_cpu_exec(CPUState *cpu)
              * still full.  Got kicked by KVM_RESET_DIRTY_RINGS.
              */
             trace_kvm_dirty_ring_full(cpu->cpu_index);
-            qemu_mutex_lock_iothread();
+            bql_lock();
             /*
              * We throttle vCPU by making it sleep once it exit from kernel
              * due to dirty ring full. In the dirtylimit scenario, reaping
@@ -2939,7 +2939,7 @@ int kvm_cpu_exec(CPUState *cpu)
             } else {
                 kvm_dirty_ring_reap(kvm_state, NULL);
             }
-            qemu_mutex_unlock_iothread();
+            bql_unlock();
             dirtylimit_vcpu_execute(cpu);
             ret = 0;
             break;
@@ -2956,9 +2956,9 @@ int kvm_cpu_exec(CPUState *cpu)
                 break;
             case KVM_SYSTEM_EVENT_CRASH:
                 kvm_cpu_synchronize_state(cpu);
-                qemu_mutex_lock_iothread();
+                bql_lock();
                 qemu_system_guest_panicked(cpu_get_crash_info(cpu));
-                qemu_mutex_unlock_iothread();
+                bql_unlock();
                 ret = 0;
                 break;
             default:
@@ -2973,7 +2973,7 @@ int kvm_cpu_exec(CPUState *cpu)
     } while (ret == 0);
 
     cpu_exec_end(cpu);
-    qemu_mutex_lock_iothread();
+    bql_lock();
 
     if (ret < 0) {
         cpu_dump_state(cpu, stderr, CPU_DUMP_CODE);