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, 13 insertions, 13 deletions

diff --git a/accel/tcg/cpu-exec.c b/accel/tcg/cpu-exec.c
index c938eb96f8..67eda9865e 100644
--- a/accel/tcg/cpu-exec.c
+++ b/accel/tcg/cpu-exec.c
@@ -558,8 +558,8 @@ static void cpu_exec_longjmp_cleanup(CPUState *cpu)
         tcg_ctx->gen_tb = NULL;
     }
 #endif
-    if (qemu_mutex_iothread_locked()) {
-        qemu_mutex_unlock_iothread();
+    if (bql_locked()) {
+        bql_unlock();
     }
     assert_no_pages_locked();
 }
@@ -680,10 +680,10 @@ static inline bool cpu_handle_halt(CPUState *cpu)
 #if defined(TARGET_I386)
         if (cpu->interrupt_request & CPU_INTERRUPT_POLL) {
             X86CPU *x86_cpu = X86_CPU(cpu);
-            qemu_mutex_lock_iothread();
+            bql_lock();
             apic_poll_irq(x86_cpu->apic_state);
             cpu_reset_interrupt(cpu, CPU_INTERRUPT_POLL);
-            qemu_mutex_unlock_iothread();
+            bql_unlock();
         }
 #endif /* TARGET_I386 */
         if (!cpu_has_work(cpu)) {
@@ -749,9 +749,9 @@ static inline bool cpu_handle_exception(CPUState *cpu, int *ret)
 #else
         if (replay_exception()) {
             CPUClass *cc = CPU_GET_CLASS(cpu);
-            qemu_mutex_lock_iothread();
+            bql_lock();
             cc->tcg_ops->do_interrupt(cpu);
-            qemu_mutex_unlock_iothread();
+            bql_unlock();
             cpu->exception_index = -1;
 
             if (unlikely(cpu->singlestep_enabled)) {
@@ -812,7 +812,7 @@ static inline bool cpu_handle_interrupt(CPUState *cpu,
 
     if (unlikely(qatomic_read(&cpu->interrupt_request))) {
         int interrupt_request;
-        qemu_mutex_lock_iothread();
+        bql_lock();
         interrupt_request = cpu->interrupt_request;
         if (unlikely(cpu->singlestep_enabled & SSTEP_NOIRQ)) {
             /* Mask out external interrupts for this step. */
@@ -821,7 +821,7 @@ static inline bool cpu_handle_interrupt(CPUState *cpu,
         if (interrupt_request & CPU_INTERRUPT_DEBUG) {
             cpu->interrupt_request &= ~CPU_INTERRUPT_DEBUG;
             cpu->exception_index = EXCP_DEBUG;
-            qemu_mutex_unlock_iothread();
+            bql_unlock();
             return true;
         }
 #if !defined(CONFIG_USER_ONLY)
@@ -832,7 +832,7 @@ static inline bool cpu_handle_interrupt(CPUState *cpu,
             cpu->interrupt_request &= ~CPU_INTERRUPT_HALT;
             cpu->halted = 1;
             cpu->exception_index = EXCP_HLT;
-            qemu_mutex_unlock_iothread();
+            bql_unlock();
             return true;
         }
 #if defined(TARGET_I386)
@@ -843,14 +843,14 @@ static inline bool cpu_handle_interrupt(CPUState *cpu,
             cpu_svm_check_intercept_param(env, SVM_EXIT_INIT, 0, 0);
             do_cpu_init(x86_cpu);
             cpu->exception_index = EXCP_HALTED;
-            qemu_mutex_unlock_iothread();
+            bql_unlock();
             return true;
         }
 #else
         else if (interrupt_request & CPU_INTERRUPT_RESET) {
             replay_interrupt();
             cpu_reset(cpu);
-            qemu_mutex_unlock_iothread();
+            bql_unlock();
             return true;
         }
 #endif /* !TARGET_I386 */
@@ -873,7 +873,7 @@ static inline bool cpu_handle_interrupt(CPUState *cpu,
                  */
                 if (unlikely(cpu->singlestep_enabled)) {
                     cpu->exception_index = EXCP_DEBUG;
-                    qemu_mutex_unlock_iothread();
+                    bql_unlock();
                     return true;
                 }
                 cpu->exception_index = -1;
@@ -892,7 +892,7 @@ static inline bool cpu_handle_interrupt(CPUState *cpu,
         }
 
         /* If we exit via cpu_loop_exit/longjmp it is reset in cpu_exec */
-        qemu_mutex_unlock_iothread();
+        bql_unlock();
     }
 
     /* Finally, check if we need to exit to the main loop.  */