From: Sunil Muthuswamy <sunilmut@xxxxxxxxxxxxx> Date: Mon, 17 Jun 2019 19:26:25 +0000 > Currently, hvsock can enter into a state where epoll_wait on EPOLLOUT will > not return even when the hvsock socket is writable, under some race > condition. This can happen under the following sequence: ... > Now, the EPOLLOUT will never return even if the socket write buffer is > empty. > > The fix is to set the pending size to the default size and never change it. > This way the host will always notify the guest whenever the writable space > is bigger than the pending size. The host is already optimized to *only* > notify the guest when the pending size threshold boundary is crossed and > not everytime. > > This change also reduces the cpu usage somewhat since hv_stream_has_space() > is in the hotpath of send: > vsock_stream_sendmsg()->hv_stream_has_space() > Earlier hv_stream_has_space was setting/clearing the pending size on every > call. > > Signed-off-by: Sunil Muthuswamy <sunilmut@xxxxxxxxxxxxx> > Reviewed-by: Dexuan Cui <decui@xxxxxxxxxxxxx> > --- > - Resubmitting the patch after taking care of some spurious warnings. Applied and queued up for -stable.
