[Qemu-devel] [PATCH 1/3] rcu: automatically unregister threads when they exit

[Paolo Bonzini <pbonzini@redhat.com>]

This simplifies management within the threads themselves.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 tests/rcutorture.c | 10 ----------
 util/rcu.c         | 12 ++++++++++++
 2 files changed, 12 insertions(+), 10 deletions(-)

diff --git a/tests/rcutorture.c b/tests/rcutorture.c
index d6b304d..000b216 100644
--- a/tests/rcutorture.c
+++ b/tests/rcutorture.c
@@ -134,8 +134,6 @@ static void *rcu_read_perf_test(void *arg)
     qemu_mutex_lock(&counts_mutex);
     n_reads += n_reads_local;
     qemu_mutex_unlock(&counts_mutex);
-
-    rcu_unregister_thread();
     return NULL;
 }
 
@@ -157,8 +155,6 @@ static void *rcu_update_perf_test(void *arg)
     qemu_mutex_lock(&counts_mutex);
     n_updates += n_updates_local;
     qemu_mutex_unlock(&counts_mutex);
-
-    rcu_unregister_thread();
     return NULL;
 }
 
@@ -283,8 +279,6 @@ static void *rcu_read_stress_test(void *arg)
         rcu_stress_count[i] += rcu_stress_local[i];
     }
     qemu_mutex_unlock(&counts_mutex);
-
-    rcu_unregister_thread();
     return NULL;
 }
 
@@ -319,8 +313,6 @@ static void *rcu_update_stress_test(void *arg)
         synchronize_rcu();
         n_updates++;
     }
-
-    rcu_unregister_thread();
     return NULL;
 }
 
@@ -336,8 +328,6 @@ static void *rcu_fake_update_stress_test(void *arg)
         synchronize_rcu();
         g_usleep(1000);
     }
-
-    rcu_unregister_thread();
     return NULL;
 }
 
diff --git a/util/rcu.c b/util/rcu.c
index 7270151..8830295 100644
--- a/util/rcu.c
+++ b/util/rcu.c
@@ -268,12 +268,22 @@ void call_rcu1(struct rcu_head *node, void (*func)(struct rcu_head *node))
     qemu_event_set(&rcu_call_ready_event);
 }
 
+static __thread Notifier unregister_thread_notifier;
+
+static void rcu_unregister_thread_notify(Notifier *n, void *data)
+{
+    rcu_unregister_thread();
+}
+
 void rcu_register_thread(void)
 {
     assert(rcu_reader.ctr == 0);
     qemu_mutex_lock(&rcu_gp_lock);
     QLIST_INSERT_HEAD(&registry, &rcu_reader, node);
     qemu_mutex_unlock(&rcu_gp_lock);
+
+    unregister_thread_notifier.notify = rcu_unregister_thread_notify;
+    qemu_thread_atexit_add(&unregister_thread_notifier);
 }
 
 void rcu_unregister_thread(void)
@@ -281,6 +291,8 @@ void rcu_unregister_thread(void)
     qemu_mutex_lock(&rcu_gp_lock);
     QLIST_REMOVE(&rcu_reader, node);
     qemu_mutex_unlock(&rcu_gp_lock);
+
+    qemu_thread_atexit_remove(&unregister_thread_notifier);
 }
 
 static void rcu_init_complete(void)
-- 
2.4.3