[Qemu-devel] [PATCH v2 2/9] cpus: Add a sync version of cpu_remove()

[Matthew Rosato <mjrosato@linux.vnet.ibm.com>]

From: 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>
Signed-off-by: Matthew Rosato <mjrosato@linux.vnet.ibm.com>
               [Call cpu_remove() directly from cpu_remove_sync()]
---
 cpus.c            | 12 ++++++++++++
 include/qom/cpu.h |  8 ++++++++
 2 files changed, 20 insertions(+)

diff --git a/cpus.c b/cpus.c
index af2b274..c2444ba 100644
--- a/cpus.c
+++ b/cpus.c
@@ -1070,6 +1070,8 @@ static void *qemu_kvm_cpu_thread_fn(void *arg)
         qemu_kvm_wait_io_event(cpu);
         if (cpu->exit && !cpu_can_run(cpu)) {
             qemu_kvm_destroy_vcpu(cpu);
+            cpu->created = false;
+            qemu_cond_signal(&qemu_cpu_cond);
             qemu_mutex_unlock(&qemu_global_mutex);
             return NULL;
         }
@@ -1174,6 +1176,8 @@ 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;
         }
     }
@@ -1339,6 +1343,14 @@ 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 6a1d887..dc2b566 100644
--- a/include/qom/cpu.h
+++ b/include/qom/cpu.h
@@ -705,6 +705,14 @@ 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.
-- 
1.9.1