On 07/27/2015 06:52 PM, Paolo Bonzini wrote: > > > On 27/07/2015 12:44, Wen Congyang wrote: >>> * rcu_register_thread() may add nodes to ®istry; it will not >>> * wake up synchronize_rcu, but that is okay because at least >>> another >>> * thread must exit its RCU read-side critical section before >>> * synchronize_rcu is done. The next iteration of the loop will >>> * process the new thread or set ->waiting for it. Hence, this can >>> * at worst cause synchronize_rcu() to wait for longer. >> I don't understand this. The next iteration of the loop will move the new >> thread's >> rcu_reader from registry to qsreaders even if we call rcu_read_lock() in the >> new thread. >> Because rcu_gp_ongoing() will return false. > > You're right. This proves that a comment was necessary! :)
Yes, I agree with it. > > Second try: > > * rcu_register_thread() may add nodes to ®istry; it will not > * wake up synchronize_rcu, but that is okay because at least another > * thread must exit its RCU read-side critical section before > * synchronize_rcu is done. The next iteration of the loop will > * move the new thread's rcu_reader from ®istry to &qsreaders, > * because rcu_gp_ongoing() will return false. I will update the comment and send it again. Thanks Wen Congyang > > Paolo > . >