On Fri, Aug 24, 2012 at 04:01:37PM +0200, Daniel Wagner wrote:
quoted hunk
@@ -306,6 +312,11 @@ static void __exit exit_cgroup_cls(void)
synchronize_rcu();
#endif
+#if IS_MODULE(CONFIG_NET_CLS_CGROUP)
+ static_key_slow_dec(&cgroup_cls_enabled);
+ rcu_barrier();
Why is this rcu_barrier() necessary? In general, please explain what
synchronization is going on when using sync constructs which aren't
obvious - e.g. memory barriers, rcu barriers.
Thanks.
--
tejun
On 25.08.2012 01:26, Tejun Heo wrote:
On Fri, Aug 24, 2012 at 04:01:37PM +0200, Daniel Wagner wrote:
quoted
@@ -306,6 +312,11 @@ static void __exit exit_cgroup_cls(void)
synchronize_rcu();
#endif
+#if IS_MODULE(CONFIG_NET_CLS_CGROUP)
+ static_key_slow_dec(&cgroup_cls_enabled);
+ rcu_barrier();
Why is this rcu_barrier() necessary?
I have read the rcubarrier.txt document and I got from that that an
rcu_barrier() is needed when unloading a module. But maybe I got it wrong.
So the idea after disabling the jump lables all pending readers in
task_cls_classid() have left. THe same thing is done in the old code
with the dynamic id part. With the difference that synchronize_rcu() is
used.
In general, please explain what
synchronization is going on when using sync constructs which aren't
obvious - e.g. memory barriers, rcu barriers.
Sure, I will keep this in mind.