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igbvf: Make next_to_watch a pointer and adjust memory barriers to avoid races

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This change is meant to address several race issues that become possible
because next_to_watch could possibly be set to a value that shows that the
descriptor is done when it is not.  In order to correct that we instead make
next_to_watch a pointer that is set to NULL during cleanup, and set to the
eop_desc after the descriptor rings have been written.

To enforce proper ordering the next_to_watch pointer is not set until after
a wmb writing the values to the last descriptor in a transmit.  In order to
guarantee that the descriptor is not read until after the eop_desc we use the
read_barrier_depends which is only really necessary on the alpha architecture.

Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
Acked-by: Greg Rose <gregory.v.rose@intel.com>
Tested-by: Sibai Li <sibai.li@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
This commit is contained in:
Alexander Duyck
2013-01-31 07:15:51 +00:00
committed by Jeff Kirsher
parent e792cd916c
commit 3eb1a40f4b
2 changed files with 31 additions and 23 deletions
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2
drivers/net/ethernet/intel/igbvf/igbvf.h
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@@ -127,8 +127,8 @@ struct igbvf_buffer {
/* Tx */
struct {
unsigned long time_stamp;
union e1000_adv_tx_desc *next_to_watch;
u16 length;
u16 next_to_watch;
u16 mapped_as_page;
};
/* Rx */