[PATCH v10 62/73] cpu: introduce cpu_has_work_with_iothread_lock

[Robert Foley]

From: "Emilio G. Cota" <cota@braap.org>

It will gain some users soon.

Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Emilio G. Cota <cota@braap.org>
Signed-off-by: Robert Foley <robert.foley@linaro.org>
---
 include/hw/core/cpu.h | 37 ++++++++++++++++++++++++++++++++++---
 1 file changed, 34 insertions(+), 3 deletions(-)

diff --git a/include/hw/core/cpu.h b/include/hw/core/cpu.h
index 79da78cd10..720bc85a84 100644
--- a/include/hw/core/cpu.h
+++ b/include/hw/core/cpu.h
@@ -26,6 +26,7 @@
 #include "exec/memattrs.h"
 #include "qapi/qapi-types-run-state.h"
 #include "qemu/bitmap.h"
+#include "qemu/main-loop.h"
 #include "qemu/rcu_queue.h"
 #include "qemu/queue.h"
 #include "qemu/thread.h"
@@ -82,6 +83,8 @@ 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_unaligned_access: Callback for unaligned access handling, if
  * the target defines #TARGET_ALIGNED_ONLY.
@@ -167,6 +170,7 @@ typedef struct CPUClass {
 
     int reset_dump_flags;
     bool (*has_work)(CPUState *cpu);
+    bool (*has_work_with_iothread_lock)(CPUState *cpu);
     void (*do_interrupt)(CPUState *cpu);
     void (*do_unaligned_access)(CPUState *cpu, vaddr addr,
                                 MMUAccessType access_type,
@@ -805,14 +809,41 @@ const char *parse_cpu_option(const char *cpu_option);
 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