From 24b8b44780a2c53ecb738f4a1c08d114f5eda27c Mon Sep 17 00:00:00 2001 From: Tom Tucker Date: Wed, 13 Aug 2008 11:05:41 -0500 Subject: [PATCH] svcrdma: Fix race between svc_rdma_recvfrom thread and the dto_tasklet RDMA_READ completions are kept on a separate queue from the general I/O request queue. Since a separate lock is used to protect the RDMA_READ completion queue, a race exists between the dto_tasklet and the svc_rdma_recvfrom thread where the dto_tasklet sets the XPT_DATA bit and adds I/O to the read-completion queue. Concurrently, the recvfrom thread checks the generic queue, finds it empty and resets the XPT_DATA bit. A subsequent svc_xprt_enqueue will fail to enqueue the transport for I/O and cause the transport to "stall". The fix is to protect both lists with the same lock and set the XPT_DATA bit with this lock held. Signed-off-by: Tom Tucker Signed-off-by: J. Bruce Fields --- include/linux/sunrpc/svc_rdma.h | 1 - net/sunrpc/xprtrdma/svc_rdma_recvfrom.c | 8 ++++---- net/sunrpc/xprtrdma/svc_rdma_transport.c | 5 ++--- 3 files changed, 6 insertions(+), 8 deletions(-) diff --git a/include/linux/sunrpc/svc_rdma.h b/include/linux/sunrpc/svc_rdma.h index ef2e3a20bf3b..dc05b54bd3a3 100644 --- a/include/linux/sunrpc/svc_rdma.h +++ b/include/linux/sunrpc/svc_rdma.h @@ -143,7 +143,6 @@ struct svcxprt_rdma { unsigned long sc_flags; struct list_head sc_dto_q; /* DTO tasklet I/O pending Q */ struct list_head sc_read_complete_q; - spinlock_t sc_read_complete_lock; struct work_struct sc_work; }; /* sc_flags */ diff --git a/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c b/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c index b4b17f44cb29..74de31a06616 100644 --- a/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c +++ b/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c @@ -443,18 +443,18 @@ int svc_rdma_recvfrom(struct svc_rqst *rqstp) dprintk("svcrdma: rqstp=%p\n", rqstp); - spin_lock_bh(&rdma_xprt->sc_read_complete_lock); + spin_lock_bh(&rdma_xprt->sc_rq_dto_lock); if (!list_empty(&rdma_xprt->sc_read_complete_q)) { ctxt = list_entry(rdma_xprt->sc_read_complete_q.next, struct svc_rdma_op_ctxt, dto_q); list_del_init(&ctxt->dto_q); } - spin_unlock_bh(&rdma_xprt->sc_read_complete_lock); - if (ctxt) + if (ctxt) { + spin_unlock_bh(&rdma_xprt->sc_rq_dto_lock); return rdma_read_complete(rqstp, ctxt); + } - spin_lock_bh(&rdma_xprt->sc_rq_dto_lock); if (!list_empty(&rdma_xprt->sc_rq_dto_q)) { ctxt = list_entry(rdma_xprt->sc_rq_dto_q.next, struct svc_rdma_op_ctxt, diff --git a/net/sunrpc/xprtrdma/svc_rdma_transport.c b/net/sunrpc/xprtrdma/svc_rdma_transport.c index 19ddc382b777..900cb69728c6 100644 --- a/net/sunrpc/xprtrdma/svc_rdma_transport.c +++ b/net/sunrpc/xprtrdma/svc_rdma_transport.c @@ -359,11 +359,11 @@ static void sq_cq_reap(struct svcxprt_rdma *xprt) if (test_bit(RDMACTXT_F_LAST_CTXT, &ctxt->flags)) { struct svc_rdma_op_ctxt *read_hdr = ctxt->read_hdr; BUG_ON(!read_hdr); + spin_lock_bh(&xprt->sc_rq_dto_lock); set_bit(XPT_DATA, &xprt->sc_xprt.xpt_flags); - spin_lock_bh(&xprt->sc_read_complete_lock); list_add_tail(&read_hdr->dto_q, &xprt->sc_read_complete_q); - spin_unlock_bh(&xprt->sc_read_complete_lock); + spin_unlock_bh(&xprt->sc_rq_dto_lock); svc_xprt_enqueue(&xprt->sc_xprt); } svc_rdma_put_context(ctxt, 0); @@ -428,7 +428,6 @@ static struct svcxprt_rdma *rdma_create_xprt(struct svc_serv *serv, init_waitqueue_head(&cma_xprt->sc_send_wait); spin_lock_init(&cma_xprt->sc_lock); - spin_lock_init(&cma_xprt->sc_read_complete_lock); spin_lock_init(&cma_xprt->sc_rq_dto_lock); cma_xprt->sc_ord = svcrdma_ord; -- 2.20.1