On Fri, May 02, 2008 at 11:28:34AM -0500, Tom Tucker wrote:
> 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 calling the function
> unnecessarily use test_and_clear_bit with the RDMAXPRT_SQ_PENDING
> flag to serialize access to the sq_cq_reap function.
OK. I won't pretend to understand much of this, but--would it be worth
pulling out the added code here into a helper function, since it now
exists in two different places? (Especially if correctness depends on
the same thing happening in both the places this bit can be cleared.)
--b.
>
> Signed-off-by: Tom Tucker <tom@xxxxxxxxxxxxxxxxxxxxx>
>
> ---
> net/sunrpc/xprtrdma/svc_rdma_transport.c | 8 ++++++--
> 1 files changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/net/sunrpc/xprtrdma/svc_rdma_transport.c b/net/sunrpc/xprtrdma/svc_rdma_transport.c
> index 1e0af2f..14f83a1 100644
> --- a/net/sunrpc/xprtrdma/svc_rdma_transport.c
> +++ b/net/sunrpc/xprtrdma/svc_rdma_transport.c
> @@ -1010,8 +1010,12 @@ int svc_rdma_send(struct svcxprt_rdma *xprt, struct ib_send_wr *wr)
> 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 */
> - sq_cq_reap(xprt);
> +
> + /* See if we can opportunistically reap SQ WR to make room */
> + 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);
> + }
>
> /* Wait until SQ WR available if SQ still full */
> wait_event(xprt->sc_send_wait,
--
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