On Wed, Jul 17, 2024 at 09:33:01AM -0400, Peter Xu wrote: > Hi, Michael, > > On Wed, Jul 17, 2024 at 04:55:52AM -0400, Michael S. Tsirkin wrote: > > I just want to understand how we managed to have two threads > > talking in parallel. BQL is normally enough, which path > > manages to invoke vhost-user with BQL not taken? > > Just check BQL taken on each vhost user invocation and > > you will figure it out. > > Prasad mentioned how the race happened in the cover letter: > > https://lore.kernel.org/r/20240711131424.181615-1-ppan...@redhat.com > > Thread-1 Thread-2 > > vhost_dev_start postcopy_ram_incoming_cleanup > vhost_device_iotlb_miss postcopy_notify > vhost_backend_update_device_iotlb vhost_user_postcopy_notifier > vhost_user_send_device_iotlb_msg vhost_user_postcopy_end > process_message_reply process_message_reply > vhost_user_read vhost_user_read > vhost_user_read_header vhost_user_read_header > "Fail to update device iotlb" "Failed to receive reply to > postcopy_end" > > The normal case should be that thread-2 is postcopy_ram_listen_thread(), > and this happens when postcopy migration is close to the end. > > Thanks, > > -- > Peter Xu
OK, so postcopy_ram_ things run without the BQL? -- MST
