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, 20 insertions, 20 deletions

diff --git a/target/arm/tcg/helper-a64.c b/target/arm/tcg/helper-a64.c
index 8ad84623d3..198b975f20 100644
--- a/target/arm/tcg/helper-a64.c
+++ b/target/arm/tcg/helper-a64.c
@@ -809,9 +809,9 @@ void HELPER(exception_return)(CPUARMState *env, uint64_t new_pc)
         goto illegal_return;
     }
 
-    qemu_mutex_lock_iothread();
+    bql_lock();
     arm_call_pre_el_change_hook(env_archcpu(env));
-    qemu_mutex_unlock_iothread();
+    bql_unlock();
 
     if (!return_to_aa64) {
         env->aarch64 = false;
@@ -876,9 +876,9 @@ void HELPER(exception_return)(CPUARMState *env, uint64_t new_pc)
      */
     aarch64_sve_change_el(env, cur_el, new_el, return_to_aa64);
 
-    qemu_mutex_lock_iothread();
+    bql_lock();
     arm_call_el_change_hook(env_archcpu(env));
-    qemu_mutex_unlock_iothread();
+    bql_unlock();
 
     return;
 
diff --git a/target/arm/tcg/m_helper.c b/target/arm/tcg/m_helper.c
index a26adb75aa..d1f1e02acc 100644
--- a/target/arm/tcg/m_helper.c
+++ b/target/arm/tcg/m_helper.c
@@ -373,8 +373,8 @@ void HELPER(v7m_preserve_fp_state)(CPUARMState *env)
     bool ts = is_secure && (env->v7m.fpccr[M_REG_S] & R_V7M_FPCCR_TS_MASK);
     bool take_exception;
 
-    /* Take the iothread lock as we are going to touch the NVIC */
-    qemu_mutex_lock_iothread();
+    /* Take the BQL as we are going to touch the NVIC */
+    bql_lock();
 
     /* Check the background context had access to the FPU */
     if (!v7m_cpacr_pass(env, is_secure, is_priv)) {
@@ -428,7 +428,7 @@ void HELPER(v7m_preserve_fp_state)(CPUARMState *env)
     take_exception = !stacked_ok &&
         armv7m_nvic_can_take_pending_exception(env->nvic);
 
-    qemu_mutex_unlock_iothread();
+    bql_unlock();
 
     if (take_exception) {
         raise_exception_ra(env, EXCP_LAZYFP, 0, 1, GETPC());
diff --git a/target/arm/tcg/op_helper.c b/target/arm/tcg/op_helper.c
index 9de0fa2d1f..105ab63ed7 100644
--- a/target/arm/tcg/op_helper.c
+++ b/target/arm/tcg/op_helper.c
@@ -482,9 +482,9 @@ void HELPER(cpsr_write_eret)(CPUARMState *env, uint32_t val)
 {
     uint32_t mask;
 
-    qemu_mutex_lock_iothread();
+    bql_lock();
     arm_call_pre_el_change_hook(env_archcpu(env));
-    qemu_mutex_unlock_iothread();
+    bql_unlock();
 
     mask = aarch32_cpsr_valid_mask(env->features, &env_archcpu(env)->isar);
     cpsr_write(env, val, mask, CPSRWriteExceptionReturn);
@@ -497,9 +497,9 @@ void HELPER(cpsr_write_eret)(CPUARMState *env, uint32_t val)
     env->regs[15] &= (env->thumb ? ~1 : ~3);
     arm_rebuild_hflags(env);
 
-    qemu_mutex_lock_iothread();
+    bql_lock();
     arm_call_el_change_hook(env_archcpu(env));
-    qemu_mutex_unlock_iothread();
+    bql_unlock();
 }
 
 /* Access to user mode registers from privileged modes.  */
@@ -858,9 +858,9 @@ void HELPER(set_cp_reg)(CPUARMState *env, const void *rip, uint32_t value)
     const ARMCPRegInfo *ri = rip;
 
     if (ri->type & ARM_CP_IO) {
-        qemu_mutex_lock_iothread();
+        bql_lock();
         ri->writefn(env, ri, value);
-        qemu_mutex_unlock_iothread();
+        bql_unlock();
     } else {
         ri->writefn(env, ri, value);
     }
@@ -872,9 +872,9 @@ uint32_t HELPER(get_cp_reg)(CPUARMState *env, const void *rip)
     uint32_t res;
 
     if (ri->type & ARM_CP_IO) {
-        qemu_mutex_lock_iothread();
+        bql_lock();
         res = ri->readfn(env, ri);
-        qemu_mutex_unlock_iothread();
+        bql_unlock();
     } else {
         res = ri->readfn(env, ri);
     }
@@ -887,9 +887,9 @@ void HELPER(set_cp_reg64)(CPUARMState *env, const void *rip, uint64_t value)
     const ARMCPRegInfo *ri = rip;
 
     if (ri->type & ARM_CP_IO) {
-        qemu_mutex_lock_iothread();
+        bql_lock();
         ri->writefn(env, ri, value);
-        qemu_mutex_unlock_iothread();
+        bql_unlock();
     } else {
         ri->writefn(env, ri, value);
     }
@@ -901,9 +901,9 @@ uint64_t HELPER(get_cp_reg64)(CPUARMState *env, const void *rip)
     uint64_t res;
 
     if (ri->type & ARM_CP_IO) {
-        qemu_mutex_lock_iothread();
+        bql_lock();
         res = ri->readfn(env, ri);
-        qemu_mutex_unlock_iothread();
+        bql_unlock();
     } else {
         res = ri->readfn(env, ri);
     }
diff --git a/target/arm/tcg/psci.c b/target/arm/tcg/psci.c
index 6c1239bb96..9080a91d9c 100644
--- a/target/arm/tcg/psci.c
+++ b/target/arm/tcg/psci.c
@@ -107,7 +107,7 @@ void arm_handle_psci_call(ARMCPU *cpu)
             }
             target_cpu = ARM_CPU(target_cpu_state);
 
-            g_assert(qemu_mutex_iothread_locked());
+            g_assert(bql_locked());
             ret = target_cpu->power_state;
             break;
         default: