amd-xgbe: Fix race between access of desc and desc index
authorLendacky, Thomas <Thomas.Lendacky@amd.com>
Mon, 26 Oct 2015 22:13:54 +0000 (17:13 -0500)
committerDavid S. Miller <davem@davemloft.net>
Wed, 28 Oct 2015 02:49:22 +0000 (19:49 -0700)
commit20986ed826cbb36bb8f2d77f872e3c52d8d30647
treeb901d1387064b7a4710227081ee23083a421d6e1
parent8ce675ff39b9958d1c10f86cf58e357efaafc856
amd-xgbe: Fix race between access of desc and desc index

During Tx cleanup it's still possible for the descriptor data to be
read ahead of the descriptor index. A memory barrier is required between
the read of the descriptor index and the start of the Tx cleanup loop.
This allows a change to a lighter-weight barrier in the Tx transmit
routine just before updating the current descriptor index.

Since the memory barrier does result in extra overhead on arm64, keep
the previous change to not chase the current descriptor value. This
prevents the execution of the barrier for each loop performed.

Suggested-by: Alexander Duyck <alexander.duyck@gmail.com>
Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
drivers/net/ethernet/amd/xgbe/xgbe-dev.c
drivers/net/ethernet/amd/xgbe/xgbe-drv.c