J. Bruce Fields wrote:
On Wed, Aug 13, 2008 at 11:05:41AM -0500, Tom Tucker wrote:
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 <tom@xxxxxxxxxxxxxxxxxxxxx>
OK. As a bugfix, would you like this sent in now for 2.6.27?
Yes I would if that's possible. I put it before all the other patches so it
would be independent.
Thanks,
Tom
--b.
---
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 ef2e3a2..dc05b54 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 b4b17f4..74de31a 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 19ddc38..900cb69 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;
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