cpu: expose qemu_cpu_list_lock for lock-guard use

Expose qemu_cpu_list_lock globally so that we can use
WITH_QEMU_LOCK_GUARD and QEMU_LOCK_GUARD to simplify a few code paths
now and in future.

Signed-off-by: Jamie Iles <quic_jiles@quicinc.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20230427020925.51003-2-quic_jiles@quicinc.com>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

cpus-common.c

@@ -25,7 +25,7 @@
 #include "qemu/lockable.h"
 #include "trace/trace-root.h"
 
-static QemuMutex qemu_cpu_list_lock;
+QemuMutex qemu_cpu_list_lock;
 static QemuCond exclusive_cond;
 static QemuCond exclusive_resume;
 static QemuCond qemu_work_cond;

include/exec/cpu-common.h

@@ -32,6 +32,7 @@ extern intptr_t qemu_host_page_mask;
 #define REAL_HOST_PAGE_ALIGN(addr) ROUND_UP((addr), qemu_real_host_page_size())
 
 /* The CPU list lock nests outside page_(un)lock or mmap_(un)lock */
+extern QemuMutex qemu_cpu_list_lock;
 void qemu_init_cpu_list(void);
 void cpu_list_lock(void);
 void cpu_list_unlock(void);

linux-user/elfload.c

@@ -17,6 +17,7 @@
 #include "qemu/guest-random.h"
 #include "qemu/units.h"
 #include "qemu/selfmap.h"
+#include "qemu/lockable.h"
 #include "qapi/error.h"
 #include "qemu/error-report.h"
 #include "target_signal.h"
@@ -4238,14 +4239,14 @@ static int fill_note_info(struct elf_note_info *info,
         info->notes_size += note_size(&info->notes[i]);
 
     /* read and fill status of all threads */
-    cpu_list_lock();
-    CPU_FOREACH(cpu) {
-        if (cpu == thread_cpu) {
-            continue;
+    WITH_QEMU_LOCK_GUARD(&qemu_cpu_list_lock) {
+        CPU_FOREACH(cpu) {
+            if (cpu == thread_cpu) {
+                continue;
+            }
+            fill_thread_info(info, cpu->env_ptr);
         }
-        fill_thread_info(info, cpu->env_ptr);
     }
-    cpu_list_unlock();
 
     return (0);
 }

migration/dirtyrate.c

@@ -150,25 +150,25 @@ int64_t vcpu_calculate_dirtyrate(int64_t calc_time_ms,
 retry:
     init_time_ms = qemu_clock_get_ms(QEMU_CLOCK_REALTIME);
 
-    cpu_list_lock();
-    gen_id = cpu_list_generation_id_get();
-    records = vcpu_dirty_stat_alloc(stat);
-    vcpu_dirty_stat_collect(stat, records, true);
-    cpu_list_unlock();
+    WITH_QEMU_LOCK_GUARD(&qemu_cpu_list_lock) {
+        gen_id = cpu_list_generation_id_get();
+        records = vcpu_dirty_stat_alloc(stat);
+        vcpu_dirty_stat_collect(stat, records, true);
+    }
 
     duration = dirty_stat_wait(calc_time_ms, init_time_ms);
 
     global_dirty_log_sync(flag, one_shot);
 
-    cpu_list_lock();
-    if (gen_id != cpu_list_generation_id_get()) {
-        g_free(records);
-        g_free(stat->rates);
-        cpu_list_unlock();
-        goto retry;
+    WITH_QEMU_LOCK_GUARD(&qemu_cpu_list_lock) {
+        if (gen_id != cpu_list_generation_id_get()) {
+            g_free(records);
+            g_free(stat->rates);
+            cpu_list_unlock();
+            goto retry;
+        }
+        vcpu_dirty_stat_collect(stat, records, false);
     }
-    vcpu_dirty_stat_collect(stat, records, false);
-    cpu_list_unlock();
 
     for (i = 0; i < stat->nvcpu; i++) {
         dirtyrate = do_calculate_dirtyrate(records[i], duration);

trace/control-target.c

@@ -8,6 +8,7 @@
  */
 
 #include "qemu/osdep.h"
+#include "qemu/lockable.h"
 #include "cpu.h"
 #include "trace/trace-root.h"
 #include "trace/control.h"
@@ -116,11 +117,9 @@ static bool adding_first_cpu1(void)
 
 static bool adding_first_cpu(void)
 {
-    bool res;
-    cpu_list_lock();
-    res = adding_first_cpu1();
-    cpu_list_unlock();
-    return res;
+    QEMU_LOCK_GUARD(&qemu_cpu_list_lock);
+
+    return adding_first_cpu1();
 }
 
 void trace_init_vcpu(CPUState *vcpu)