05/07/2018 05:37, Zhang, Qi Z: > From: Thomas Monjalon [mailto:tho...@monjalon.net] > > 05/07/2018 03:38, Zhang, Qi Z: > > > From: Thomas Monjalon [mailto:tho...@monjalon.net] > > > > 04/07/2018 12:49, Zhang, Qi Z: > > > > > From: Thomas Monjalon [mailto:tho...@monjalon.net] > > > > > > 04/07/2018 03:47, Zhang, Qi Z: > > > > > > > From: Thomas Monjalon [mailto:tho...@monjalon.net] > > > > > > > > 03/07/2018 17:08, Zhang, Qi Z: > > > > > > > > > From: Thomas Monjalon [mailto:tho...@monjalon.net] > > > > > > > > > > 02/07/2018 07:44, Qi Zhang: > > > > > > > > > > > Introduce API rte_eth_dev_lock and rte_eth_dev_unlock > > > > > > > > > > > to let application lock or unlock on specific ethdev, > > > > > > > > > > > a locked device can't be detached, this help > > > > > > > > > > > applicaiton to prevent unexpected device detaching, > > > > > > > > > > > especially in multi-process > > > > envrionment. > > > > > > > > > > > > > > > > > > > > Trying to understand: a process of an application could > > > > > > > > > > try to detach a port while another process is against this > > decision. > > > > > > > > > > Why an application needs to be protected against itself? > > > > > > > > > > > > > > > > > > I think we can regard this as a help function, it help > > > > > > > > > application to simplified > > > > > > > > the situation when one process want to detach a device while > > > > > > > > another one is still using it. > > > > > > > > > Application can register a callback which can do to > > > > > > > > > necessary clean up (like > > > > > > > > stop traffic, release memory ...) before device be detached. > > > > > > > > > > > > > > > > Yes I agree such hook can be a good idea. > > > > [...] > > > > > > > > After all, it is just a pre-detach hook. > > > > > > > > > > > > > > > Wait, how is it different of RTE_ETH_EVENT_DESTROY callback? > > > > > > > > Perhaps we just need to improve the handling of the DESTROY > > event? > > > > > > > > > > > > > > I have thought about this before. > > > > > > > Not like RTE_ETH_EVENT_DESTROY and other event hook, the hook > > > > > > > here > > > > > > need to give feedback, pass or fail will impact the following > > > > > > behavior, this make it special, so I separate it from all exist > > > > > > rte_eth_event_type handle mechanism. > > > > > > > > > > > > Look at _rte_eth_dev_callback_process, there is a "ret_param". > > > > > > > > > > OK, that should work. > > > > > > > > > > > > > The alternative solution is > > > > > > > we just introduce a new event type like > > > > > > > RTE_ETH_EVENT_PRE_DETACH and reuse all exist API > > > > > > rte_eth_dev_callback_register/rte_eth_dev_callback_unregister. > > > > > > > > > > > > I don't think we need a new event. > > > > > > Let's try to use RTE_ETH_EVENT_DESTROY. > > > > > > > > > > The problem is RTE_ETH_EVENT_DESTROY is used in > > > > rte_eth_dev_release_port already. > > > > > And in PMD, rte_eth_dev_release_port is called after dev_uninit, > > > > > that mean its too late to reject a detach > > > > > > > > You're right. > > > > > > > > It's a real mess currently. > > > > The right order should be to remove ethdev ports before removing the > > > > underlying EAL device. But it's strangely not the case. > > > > > > > > We need to separate things. > > > > The function rte_eth_dev_close can be used to remove an ethdev port > > > > if we add a call to rte_eth_dev_release_port. > > > > So we could call rte_eth_dev_close in PMD remove functions. > > > > Is "close" a good time to ask confirmation to the application? > > > > Or should we ask confirmation a step before, on "stop"? > > > > > > I think the confirmation should before any cleanup stage, it should at the > > beginning of driver->remove. > > > > So you stop a port, even if the app policy is against detaching it? > > My understanding is, stop and detach is different, we may stop a device and > reconfigure it then restart it. > but for detach, properly we will not use it, unless it be probed again. > For dev_close , it should be called after dev_stop. > so we have to like below. > > If (dev->started) { > dev_stop /* but still problem here, if traffic is ongoing */ > if (dev_close()) { > dev_start() > return -EBUSY. > } > } else { > If (dev_close()) > Return _EBUSY > } > > So for me, neither rte_eth_dev_stop and rte_eth_dev_close is the right place > to check this. > But rte_eth_dev_destroy looks like a good one. We can put all the ethdev > general logic into it, > and PMD specific dev_unit will be called at last
If you want to detach a port, you need to stop it. If one process try to detach a port, but another process decides (via callback) that the port should not be detached, you will have stopped a port for no good reason. To me it is a real design issue. > > > Also we should not put it into rte_eth_dev_stop, because, rte_eth_dev_stop > > can invoked by application directly, in that case, we don't what any > > callback be > > invoked. > > > > It it the same to detach a port: it is invoked directly by application. > > I thought you wanted a callback as helper for inter-process management? > > > > > > > So , do you mean we can remove > > > > > _rte_eth_dev_callback_process(RTE_ETH_EVENT_DESTROPY) in > > > > > rte_eth_dev_release_port > > > > > > > > I would say we need RTE_ETH_EVENT_DESTROY to notify that the port is > > > > really destroyed. > > > > Maybe the right thing to do is to add a new event > > > > RTE_ETH_EVENT_CLOSE_REQUEST or something else. > > > > Note that we already have 2 removal events in ethdev: > > > > - RTE_ETH_EVENT_INTR_RMV when the port cannot be used anymore > > > > - RTE_ETH_EVENT_DESTROY when the port is going to be deleted > > > > > > > > > And where is right place to call > > > > _rte_eth_dev_callback_process(RTE_ETH_EVENT_DESTROY)? > > > > > If can't be called in rte_eth_dev_detach, because if device is > > > > > removed by > > > > rte_eal_hotplug_remove, it will be skipped. > > > > > > > > No, rte_eth_dev_detach and rte_eal_hotplug_remove are 2 different > > things. > > > > One is a mix of ethdev and EAL (and should be deprecated), the other > > > > one is for the underlying device at EAL level. > > > > > > > > > probably we need to call this at the beginning of each PMD > > > > > driver->remove?, > > > > that means, we need to change all PMD drivers? > > > > > > > > Yes, we can call rte_eth_dev_stop and rte_eth_dev_close at the > > > > beginning of PMD remove. > > > > Note that there is already a helper rte_eth_dev_destroy called in > > > > some PMD to achieve the removal, but curiously, it doesn't call stop and > > close functions. > > > > > > Currently PMD implement driver->remove with different way, > > rte_eth_dev_stop / rte_eth_dev_close / rte_eth_dev_destroy is not always be > > invoked. > > > So Before we standardize what ethdev API and what sequence should be > > > called in driver->remove (I think this is a separate task) I will > > > suggest 1. Create another help function like > > > _rte_eth_dev_allow_to_remove, 2. the help function will call > > _rte_eth_dev_callback_process(RTE_ETH_EVENT_PRE_REMOVE) and update > > ret_param which contain a reject count. > > > 3. the help function should to invoked at beginning at driver->remove and > > driver->remove will abort if the help function failed. > > > > > > But once we standardized that , we can do cleanup to merge it into another > > rte_eth_xxx API in next step. > > > > > > What do you think? > > > > No > > All the problems we have today are because we preferred add more and more > > functions instead of fixing the basic stuff. And it is especially the case > > for all the > > detach crap. > > So no. > > Let's fix stuff first. > > > > >
