| Message ID | 20190930090455.10772-1-metze@samba.org (mailing list archive) |
|---|---|
| State | Rejected |
| Delegated to: | Jason Gunthorpe |
| Headers | show |
| Series | rdma/core: add __module_get()/module_put() to cma_[de]ref_dev() | expand |
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@samba.org> > Cc: stable@vger.kernel.org > --- > 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? 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. 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? I think the proper thing is to fix rxe (and probably siw) to signal the DEVICE_FATAL so the CMA listeners can cleanly disconnect Jason
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@samba.org> >> Cc: stable@vger.kernel.org >> --- >> 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. Can you give me an explicit example of what the backtrace would look like for the code that triggers IB_EVENT_DEVICE_FATAL? > 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? For filesystems it typically not allowed that the driver is unloaded while it's mounted. > 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()? Thanks! metze
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@samba.org> > >> Cc: stable@vger.kernel.org > >> 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
>>> 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 Ok. >>> 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. Ok, thanks! I'll take a look at it. > 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.. On the client: rdma_create_id() rdma_resolve_addr() rdma_resolve_route() rdma_connect() On the server: rdma_create_id() rdma_bind_addr() rdma_listen() rdma_accept() I just pass in an ipv4 or ipv6 addresses. metze
On Wed, Oct 02, 2019 at 12:03:14AM +0200, Stefan Metzmacher wrote: > >>> 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 > > Ok. > > >>> 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. > > Ok, thanks! I'll take a look at it. > > > 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.. > > On the client: > > rdma_create_id() > rdma_resolve_addr() > rdma_resolve_route() > rdma_connect() > > On the server: > rdma_create_id() > rdma_bind_addr() > rdma_listen() > rdma_accept() > > I just pass in an ipv4 or ipv6 addresses. Ah, the only working flow today is to destroy your IDs when a remove comes, and CM IDs become linked to a single rdma device so you know which IDs to tear down on destroy Jason
diff --git a/drivers/infiniband/core/cma.c b/drivers/infiniband/core/cma.c index a68d0ccf67a4..d10f3d01fa02 100644 --- a/drivers/infiniband/core/cma.c +++ b/drivers/infiniband/core/cma.c @@ -276,6 +276,7 @@ enum { void cma_ref_dev(struct cma_device *cma_dev) { atomic_inc(&cma_dev->refcount); + __module_get(cma_dev->device->ops.owner); } struct cma_device *cma_enum_devices_by_ibdev(cma_device_filter filter, @@ -512,6 +513,7 @@ static void cma_attach_to_dev(struct rdma_id_private *id_priv, void cma_deref_dev(struct cma_device *cma_dev) { + module_put(cma_dev->device->ops.owner); if (atomic_dec_and_test(&cma_dev->refcount)) complete(&cma_dev->comp); }
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@samba.org> Cc: stable@vger.kernel.org --- drivers/infiniband/core/cma.c | 2 ++ 1 file changed, 2 insertions(+)