The last bit written to a completion descriptor by hardware is the color
bit. Driver must read all other descriptor fields only after reading the
color bit to avoid reading stale descriptor fields.  There is a rmb() after
reading the color bit to avoid any compiler/cpu reordering of the reads.
The color bit is the generation bit that toggles each pass through the
completion descriptor ring.
Signed-off-by: NScott Feldman <scofeldm@cisco.com>
Signed-off-by: NVasanthy Kolluri <vkolluri@cisco.com>
Signed-off-by: NRoopa Prabhu <roprabhu@cisco.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Signed-off-by: NScott Feldman <scofeldm@cisco.com>
Signed-off-by: NJeff Garzik <jgarzik@redhat.com>