Hi Ferruh, I remembered now the motivation behind separating rte_kni_release() and rte_kni_free().
The problem is that the DPDK thread which calls rte_kni_release() _cannot_ be the same thread which handles callbacks from the KNI driver via rte_kni_handle_request(). This is because the thread which calls rte_kni_release() will be stuck down in ioctl(RTE_KNI_IOCTL_RELEASE) when the kernel calls the RTE_KNI_REQ_CFG_NETWORK_IF callback to the DPDK application. Since that thread cannot call rte_kni_handle_request(), the callback would then just timeout unless some other thread calls rte_kni_handle_request(). So then you are in a bit of a chicken and egg situation. You _have_ to have a separate thread calling rte_kni_handle_request periodically, but that thread also _cannot_ run after rte_kni_release returns (actually it's worse than that because it's actually after the ioctl(RTE_KNI_IOCTL_RELEASE) returns and the fifos are freed). So in order to resolve this, I separated the release from the freeing stages. This allows the DPDK application to keep the rte_kni_handle_request() thread running while rte_kni_release() is called so that it can handle the interface state callback, then kill that thread so that it cannot touch any 'struct rte_kni' resources, then free the struct rte_kni resources. thanks dan On Wed, Aug 29, 2018 at 7:59 AM, Ferruh Yigit <ferruh.yi...@intel.com> wrote: >> When the kernel network interface is removed with unregister_netdev(), >> if the interface is up, it will generate a callback to mark the >> interface down, which calls kni_net_release(). kni_net_release() will >> block waiting for the DPDK application to call rte_kni_handle_request() >> to handle the callback, but it also needs the thread in the KNI driver >> (either the per-dev thread for multi-thread or the per-driver thread) >> to call kni_net_poll_resp() in order to wake the thread sleeping in >> kni_net_release (actually kni_net_process_request()). >> >> So now, KNI interfaces should be removed as such: >> >> 1) The user calls rte_kni_release(). This only unregisters the >> netdev in the kernel, but touches nothing else. This allows all the >> threads to run which are necessary to handle the callback into the >> DPDK application to mark the interface down. >> >> 2) The user stops the thread running rte_kni_handle_request(). >> After rte_kni_release() has been called, there will be no more >> callbacks for that interface so it is not necessary. It cannot be >> running at the same time that rte_kni_free() frees all of the FIFOs >> and DPDK memory for that KNI interface. >> >> 3) The user calls rte_kni_free(). This performs the RTE_KNI_IOCTL_FREE >> ioctl which calls kni_ioctl_free(). This function removes the struct >> kni_dev from the list of interfaces to poll (and kills the per-dev >> kthread, if configured for multi-thread), then frees the memory in >> the FIFOs.
