Roland Dreier 31d1e340f0 RDMA/nes: Remove volatile qualifier from struct nes_hw_cq.cq_vbase ... Remove the volatile qualifier from the cq_vbase member of struct nes_hw_cq, and add an rmb() in the one place where it looks like access order might make a difference. As usual, removing a volatile qualifier in a declaration is actually a bug fix, since a volatile qualifier is not sufficient to make sure that aggressively out-of-order CPUs don't reorder things and cause incorrect results. For example, a CPU might speculatively execute reads of other cqe fields before the NIC hardware has written those fields and before it has set the NES_CQE_VALID bit (even though those reads come after the test of the NES_CQE_VALID bit in program order), but then when the CPU actually executes the conditional test of the NES_CQE_VALID, the bit has been set, and the CPU will proceed with the results of the earlier speculative execution and end up using bogus data. This also gets rid of the warning: drivers/infiniband/hw/nes/nes_verbs.c: In function 'nes_destroy_cq': drivers/infiniband/hw/nes/nes_verbs.c:1978: warning: passing argument 3 of 'pci_free_consistent' discards qualifiers from pointer target type Signed-off-by: Roland Dreier <rolandd@cisco.com>		2008-04-23 11:55:45 -07:00
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