On Mon, Sep 30, 2019 at 03:52:51PM +0200, Stefan Metzmacher wrote: > Am 30.09.19 um 14:41 schrieb Jason Gunthorpe: > > On Mon, Sep 30, 2019 at 11:04:55AM +0200, Stefan Metzmacher wrote: > >> Currently there seems to be a problem when an RDMA listener or connection > >> is active on an ib_device. > >> > >> 'rmmod rdma_rxe' (the same for 'siw' and most likely all > >> others) just hangs like this until shutdown the listeners and > >> connections: > >> > >> [<0>] remove_client_context+0x97/0xe0 [ib_core] > >> [<0>] disable_device+0x90/0x120 [ib_core] > >> [<0>] __ib_unregister_device+0x41/0xa0 [ib_core] > >> [<0>] ib_unregister_driver+0xbb/0x100 [ib_core] > >> [<0>] rxe_module_exit+0x1a/0x8aa [rdma_rxe] > >> [<0>] __x64_sys_delete_module+0x147/0x290 > >> [<0>] do_syscall_64+0x5a/0x130 > >> [<0>] entry_SYSCALL_64_after_hwframe+0x44/0xa9 > >> > >> The following would be expected: > >> > >> rmmod: ERROR: Module rdma_rxe is in use > >> > >> And this change provides that. > >> > >> Once all add listeners and connections are gone > >> the module can be removed again. > >> > >> Signed-off-by: Stefan Metzmacher <metze@xxxxxxxxx> > >> Cc: stable@xxxxxxxxxxxxxxx > >> drivers/infiniband/core/cma.c | 2 ++ > >> 1 file changed, 2 insertions(+) > > > > How do you even get here? Are you using in-kernel modules to access > > rxe? > > Yes, I'm testing my smbdirect driver with Samba. > https://git.samba.org/?p=metze/linux/smbdirect.git;a=summary > > Samba's 'smbd' listens for incoming connections. > > > Drivers are supposed to declare a DEVICE_FATAL error when their module > > is removed and then progress toward cleaning up. It would seem this is > > missing in rxe. > > It's a bit hard for me to follow the code path from other drivers > and how an unload of them would trigger IB_EVENT_DEVICE_FATAL. I think the drivers just call a ib_dispatch_event on IB_EVENT_DEVICE_FATAL when they start to remove, ie before calling ib_device_unregister() > > Globally blocking module unload would break the existing dis-associate > > flows, and blocking until listeners are removed seems like all rdma > > drivers will instantly become permanetly blocked when things like SRP > > or IPoIB CM mode are running? > > So the design is to allow drivers to be unloaded while there are > active connections? > > If so is this specific to RDMA drivers? No, it is normal for networking, you can ip link set down and unload a net driver even though there are sockets open that might traverse it > > I think the proper thing is to fix rxe (and probably siw) to signal > > the DEVICE_FATAL so the CMA listeners can cleanly disconnect > > I just found that drivers/nvme/host/rdma.c and > drivers/nvme/target/rdma.c both use ib_register_client(); > in order to get notified that a device is going to be removed. > > Maybe I should also use ib_register_client()? Oh, yes, all kernel clients must use register_client and related to manage their connection to the RDMA stack otherwise they are probably racy. The remove callback there is the same idea as the device_fatal scheme is for userspace. How do you discover the RDMA device to use? Just call into CM and let it sort it out? That actually seems reasonable, but then CM should take care of the remove() to kill connections, I suppose it doesn't.. Jason
