[Qemu-devel] [RFC PATCH v2 4/9] cpu: Add a sync version of cpu_remove()

[Bharata B Rao <bharata@linux.vnet.ibm.com>]

This sync API will be used by the CPU hotplug code to wait for the CPU to
completely get removed before flagging the failure to the device_add
command.

Sync version of this call is needed to correctly recover from CPU
realization failures when ->plug() handler fails.

Signed-off-by: Bharata B Rao <bharata@linux.vnet.ibm.com>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
---
 cpus.c            | 12 ++++++++++++
 include/qom/cpu.h |  8 ++++++++
 2 files changed, 20 insertions(+)

diff --git a/cpus.c b/cpus.c
index be0ac6a..05cb096 100644
--- a/cpus.c
+++ b/cpus.c
@@ -1068,6 +1068,8 @@ static void *qemu_kvm_cpu_thread_fn(void *arg)
     } while (!cpu->unplug || cpu_can_run(cpu));
 
     qemu_kvm_destroy_vcpu(cpu);
+    cpu->created = false;
+    qemu_cond_signal(&qemu_cpu_cond);
     qemu_mutex_unlock_iothread();
     return NULL;
 }
@@ -1168,6 +1170,8 @@ static void *qemu_tcg_cpu_thread_fn(void *arg)
         }
         if (remove_cpu) {
             qemu_tcg_destroy_vcpu(remove_cpu);
+            cpu->created = false;
+            qemu_cond_signal(&qemu_cpu_cond);
             remove_cpu = NULL;
         }
     }
@@ -1333,6 +1337,14 @@ void cpu_remove(CPUState *cpu)
     qemu_cpu_kick(cpu);
 }
 
+void cpu_remove_sync(CPUState *cpu)
+{
+    cpu_remove(cpu);
+    while (cpu->created) {
+        qemu_cond_wait(&qemu_cpu_cond, &qemu_global_mutex);
+    }
+}
+
 /* For temporary buffers for forming a name */
 #define VCPU_THREAD_NAME_SIZE 16
 
diff --git a/include/qom/cpu.h b/include/qom/cpu.h
index 0720dd7..6e20119 100644
--- a/include/qom/cpu.h
+++ b/include/qom/cpu.h
@@ -765,6 +765,14 @@ void cpu_resume(CPUState *cpu);
  */
 void cpu_remove(CPUState *cpu);
 
+ /**
+ * cpu_remove_sync:
+ * @cpu: The CPU to remove.
+ *
+ * Requests the CPU to be removed and waits till it is removed.
+ */
+void cpu_remove_sync(CPUState *cpu);
+
 /**
  * qemu_init_vcpu:
  * @cpu: The vCPU to initialize.
-- 
2.1.0