svcrdma: Fix race with dto_tasklet in svc_rdma_send
The svc_rdma_send function will attempt to reap SQ WR to make room for
a new request if it finds the SQ full. This function races with the
dto_tasklet that also reaps SQ WR. To avoid polling and arming the CQ
unnecessarily move the test_and_clear_bit of the RDMAXPRT_SQ_PENDING
flag and arming of the CQ to the sq_cq_reap function.
Refactor the rq_cq_reap function to match sq_cq_reap so that the
code is easier to follow.
Signed-off-by: Tom Tucker <tom@opengridcomputing.com>
diff --git a/net/sunrpc/xprtrdma/svc_rdma_transport.c b/net/sunrpc/xprtrdma/svc_rdma_transport.c
index 1e0af2f..7373417 100644
--- a/net/sunrpc/xprtrdma/svc_rdma_transport.c
+++ b/net/sunrpc/xprtrdma/svc_rdma_transport.c
@@ -228,23 +228,8 @@
list_del_init(&xprt->sc_dto_q);
spin_unlock_irqrestore(&dto_lock, flags);
- if (test_and_clear_bit(RDMAXPRT_RQ_PENDING, &xprt->sc_flags)) {
- ib_req_notify_cq(xprt->sc_rq_cq, IB_CQ_NEXT_COMP);
- rq_cq_reap(xprt);
- set_bit(XPT_DATA, &xprt->sc_xprt.xpt_flags);
- /*
- * If data arrived before established event,
- * don't enqueue. This defers RPC I/O until the
- * RDMA connection is complete.
- */
- if (!test_bit(RDMAXPRT_CONN_PENDING, &xprt->sc_flags))
- svc_xprt_enqueue(&xprt->sc_xprt);
- }
-
- if (test_and_clear_bit(RDMAXPRT_SQ_PENDING, &xprt->sc_flags)) {
- ib_req_notify_cq(xprt->sc_sq_cq, IB_CQ_NEXT_COMP);
- sq_cq_reap(xprt);
- }
+ rq_cq_reap(xprt);
+ sq_cq_reap(xprt);
svc_xprt_put(&xprt->sc_xprt);
spin_lock_irqsave(&dto_lock, flags);
@@ -297,6 +282,10 @@
struct ib_wc wc;
struct svc_rdma_op_ctxt *ctxt = NULL;
+ if (!test_and_clear_bit(RDMAXPRT_RQ_PENDING, &xprt->sc_flags))
+ return;
+
+ ib_req_notify_cq(xprt->sc_rq_cq, IB_CQ_NEXT_COMP);
atomic_inc(&rdma_stat_rq_poll);
spin_lock_bh(&xprt->sc_rq_dto_lock);
@@ -316,6 +305,15 @@
if (ctxt)
atomic_inc(&rdma_stat_rq_prod);
+
+ set_bit(XPT_DATA, &xprt->sc_xprt.xpt_flags);
+ /*
+ * If data arrived before established event,
+ * don't enqueue. This defers RPC I/O until the
+ * RDMA connection is complete.
+ */
+ if (!test_bit(RDMAXPRT_CONN_PENDING, &xprt->sc_flags))
+ svc_xprt_enqueue(&xprt->sc_xprt);
}
/*
@@ -328,6 +326,11 @@
struct ib_cq *cq = xprt->sc_sq_cq;
int ret;
+
+ if (!test_and_clear_bit(RDMAXPRT_SQ_PENDING, &xprt->sc_flags))
+ return;
+
+ ib_req_notify_cq(xprt->sc_sq_cq, IB_CQ_NEXT_COMP);
atomic_inc(&rdma_stat_sq_poll);
while ((ret = ib_poll_cq(cq, 1, &wc)) > 0) {
ctxt = (struct svc_rdma_op_ctxt *)(unsigned long)wc.wr_id;
@@ -1010,7 +1013,8 @@
if (xprt->sc_sq_depth == atomic_read(&xprt->sc_sq_count)) {
spin_unlock_bh(&xprt->sc_lock);
atomic_inc(&rdma_stat_sq_starve);
- /* See if we can reap some SQ WR */
+
+ /* See if we can opportunistically reap SQ WR to make room */
sq_cq_reap(xprt);
/* Wait until SQ WR available if SQ still full */