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svcrdma: Fix race between svc_rdma_recvfrom thread and the dto_tasklet

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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@opengridcomputing.com>
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
This commit is contained in:
Tom Tucker 2008-08-13 11:05:41 -05:00 • committed by J. Bruce Fields
parent 30a2f3c60a
commit 24b8b44780
3 changed files with 6 additions and 8 deletions
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1
include/linux/sunrpc/svc_rdma.h
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@ -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 */