[Qemu-devel] [PATCH v7 62/73] cpu: introduce cpu_has_work_with_iothread_lock

[Emilio G. Cota]

It will gain some users soon.

Suggested-by: Paolo Bonzini <address@hidden>
Reviewed-by: Richard Henderson <address@hidden>
Reviewed-by: Alex Bennée <address@hidden>
Signed-off-by: Emilio G. Cota <address@hidden>
---
 include/qom/cpu.h | 37 ++++++++++++++++++++++++++++++++++---
 1 file changed, 34 insertions(+), 3 deletions(-)

diff --git a/include/qom/cpu.h b/include/qom/cpu.h
index 651e1ab4d8..fc768bbe00 100644
--- a/include/qom/cpu.h
+++ b/include/qom/cpu.h
@@ -27,6 +27,7 @@
 #include "qapi/qapi-types-run-state.h"
 #include "qemu/bitmap.h"
 #include "qemu/fprintf-fn.h"
+#include "qemu/main-loop.h"
 #include "qemu/rcu_queue.h"
 #include "qemu/queue.h"
 #include "qemu/thread.h"
@@ -87,6 +88,8 @@ struct TranslationBlock;
  * @reset_dump_flags: #CPUDumpFlags to use for reset logging.
  * @has_work: Callback for checking if there is work to do. Called with the
  * CPU lock held.
+ * @has_work_with_iothread_lock: Callback for checking if there is work to do.
+ * Called with both the BQL and the CPU lock held.
  * @do_interrupt: Callback for interrupt handling.
  * @do_unassigned_access: Callback for unassigned access handling.
  * (this is deprecated: new targets should use do_transaction_failed instead)
@@ -170,6 +173,7 @@ typedef struct CPUClass {
     void (*reset)(CPUState *cpu);
     int reset_dump_flags;
     bool (*has_work)(CPUState *cpu);
+    bool (*has_work_with_iothread_lock)(CPUState *cpu);
     void (*do_interrupt)(CPUState *cpu);
     CPUUnassignedAccess do_unassigned_access;
     void (*do_unaligned_access)(CPUState *cpu, vaddr addr,
@@ -809,14 +813,41 @@ const char *parse_cpu_model(const char *cpu_model);
 static inline bool cpu_has_work(CPUState *cpu)
 {
     CPUClass *cc = CPU_GET_CLASS(cpu);
+    bool has_cpu_lock = cpu_mutex_locked(cpu);
+    bool (*func)(CPUState *cpu);
     bool ret;
 
+    /* some targets require us to hold the BQL when checking for work */
+    if (cc->has_work_with_iothread_lock) {
+        if (qemu_mutex_iothread_locked()) {
+            func = cc->has_work_with_iothread_lock;
+            goto call_func;
+        }
+
+        if (has_cpu_lock) {
+            /* avoid deadlock by acquiring the locks in order */
+            cpu_mutex_unlock(cpu);
+        }
+        qemu_mutex_lock_iothread();
+        cpu_mutex_lock(cpu);
+
+        ret = cc->has_work_with_iothread_lock(cpu);
+
+        qemu_mutex_unlock_iothread();
+        if (!has_cpu_lock) {
+            cpu_mutex_unlock(cpu);
+        }
+        return ret;
+    }
+
     g_assert(cc->has_work);
-    if (cpu_mutex_locked(cpu)) {
-        return cc->has_work(cpu);
+    func = cc->has_work;
+ call_func:
+    if (has_cpu_lock) {
+        return func(cpu);
     }
     cpu_mutex_lock(cpu);
-    ret = cc->has_work(cpu);
+    ret = func(cpu);
     cpu_mutex_unlock(cpu);
     return ret;
 }
-- 
2.17.1