[Qemu-devel] [PATCH 1/3] rcu: do not let RCU callbacks pile up indefinitely

[Paolo Bonzini <pbonzini@redhat.com>]

Always process them within half a second.  Even though waiting a little
is useful, it is not okay to delay e.g. qemu_opts_del forever.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 util/rcu.c | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/util/rcu.c b/util/rcu.c
index c9c3e6e..486d7b6 100644
--- a/util/rcu.c
+++ b/util/rcu.c
@@ -223,14 +223,16 @@ static void *call_rcu_thread(void *opaque)
          * Fetch rcu_call_count now, we only must process elements that were
          * added before synchronize_rcu() starts.
          */
-        while (n < RCU_CALL_MIN_SIZE && ++tries <= 5) {
-            g_usleep(100000);
-            qemu_event_reset(&rcu_call_ready_event);
-            n = atomic_read(&rcu_call_count);
-            if (n < RCU_CALL_MIN_SIZE) {
-                qemu_event_wait(&rcu_call_ready_event);
+        while (n == 0 || (n < RCU_CALL_MIN_SIZE && ++tries <= 5)) {
+            g_usleep(10000);
+            if (n == 0) {
+                qemu_event_reset(&rcu_call_ready_event);
                 n = atomic_read(&rcu_call_count);
+                if (n == 0) {
+                    qemu_event_wait(&rcu_call_ready_event);
+                }
             }
+            n = atomic_read(&rcu_call_count);
         }
 
         atomic_sub(&rcu_call_count, n);
-- 
1.8.3.1