RDMA core mutex locking was restructured by d114c6feedfe ("RDMA/cma:
Add missing locking to rdma_accept()") [Aug 2020]. When lock
debugging is enabled, the RPC/RDMA server trips over the new lockdep
assertion in rdma_accept() because it doesn't call rdma_accept()
from its CM event handler.
As a temporary fix, have svc_rdma_accept() take the handler_mutex
explicitly. In the meantime, let's consider how to restructure the
RPC/RDMA transport to invoke rdma_accept() from the proper context.
Calls to svc_rdma_accept() are serialized with calls to
svc_rdma_free() by the generic RPC server layer.
Suggested-by: Jason Gunthorpe <[email protected]>
Link: https://lore.kernel.org/linux-rdma/[email protected]/
Fixes: d114c6feedfe ("RDMA/cma: Add missing locking to rdma_accept()")
Signed-off-by: Chuck Lever <[email protected]>
---
net/sunrpc/xprtrdma/svc_rdma_transport.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/net/sunrpc/xprtrdma/svc_rdma_transport.c b/net/sunrpc/xprtrdma/svc_rdma_transport.c
index afba4e9d5425..c895f80df659 100644
--- a/net/sunrpc/xprtrdma/svc_rdma_transport.c
+++ b/net/sunrpc/xprtrdma/svc_rdma_transport.c
@@ -475,9 +475,6 @@ static struct svc_xprt *svc_rdma_accept(struct svc_xprt *xprt)
if (!svc_rdma_post_recvs(newxprt))
goto errout;
- /* Swap out the handler */
- newxprt->sc_cm_id->event_handler = svc_rdma_cma_handler;
-
/* Construct RDMA-CM private message */
pmsg.cp_magic = rpcrdma_cmp_magic;
pmsg.cp_version = RPCRDMA_CMP_VERSION;
@@ -498,7 +495,10 @@ static struct svc_xprt *svc_rdma_accept(struct svc_xprt *xprt)
}
conn_param.private_data = &pmsg;
conn_param.private_data_len = sizeof(pmsg);
+ rdma_lock_handler(newxprt->sc_cm_id);
+ newxprt->sc_cm_id->event_handler = svc_rdma_cma_handler;
ret = rdma_accept(newxprt->sc_cm_id, &conn_param);
+ rdma_unlock_handler(newxprt->sc_cm_id);
if (ret) {
trace_svcrdma_accept_err(newxprt, ret);
goto errout;