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myri10ge: small rx_done refactoring

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Avoid theoretical race condition regarding accessing dev->features
NETIF_F_LRO flag, which is illustrated below.

CPU1					CPU2

myri10ge_clean_rx_done():		myri10ge_set_flags():
					or
					myri10ge_set_rx_csum():

if (dev->features & NETIF_F_LRO)
        setup lro
					dev->features |= NETIF_F_LRO
					or
					dev->features &= ~NETIF_F_LRO;
if (dev->features & NETIF_F_LRO)
        flush lro

On the way reduce myri10ge_rx_done() number of arguments and calls by
moving mgp->small_bytes check into that function. That reduce code size

from:
   text	   data	    bss	    dec	    hex	filename
  36644	    248	    100	  36992	   9080	drivers/net/myri10ge/myri10ge.o

to:
   text	   data	    bss	    dec	    hex	filename
  36037	    247	    100	  36384	   8e20	drivers/net/myri10ge/myri10ge.o

on my i686 system, what should also make myri10ge_clean_rx_done()
being faster.

Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Stanislaw Gruszka 2011-03-25 01:21:51 +00:00 committed by David S. Miller
parent edf947f100
commit b3cd965739
1 changed files with 23 additions and 14 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

37
drivers/net/myri10ge/myri10ge.c
View File

@ -1312,17 +1312,26 @@ myri10ge_unmap_rx_page(struct pci_dev *pdev,
* page into an skb */
static inline int
myri10ge_rx_done(struct myri10ge_slice_state *ss, struct myri10ge_rx_buf *rx,
int bytes, int len, __wsum csum)
myri10ge_rx_done(struct myri10ge_slice_state *ss, int len, __wsum csum,
int lro_enabled)
{
struct myri10ge_priv *mgp = ss->mgp;
struct sk_buff *skb;
struct skb_frag_struct rx_frags[MYRI10GE_MAX_FRAGS_PER_FRAME];
int i, idx, hlen, remainder;
struct myri10ge_rx_buf *rx;
int i, idx, hlen, remainder, bytes;
struct pci_dev *pdev = mgp->pdev;
struct net_device *dev = mgp->dev;
u8 *va;
if (len <= mgp->small_bytes) {
rx = &ss->rx_small;
bytes = mgp->small_bytes;
} else {
rx = &ss->rx_big;
bytes = mgp->big_bytes;
}
len += MXGEFW_PAD;
idx = rx->cnt & rx->mask;
va = page_address(rx->info[idx].page) + rx->info[idx].page_offset;
@ -1341,7 +1350,7 @@ myri10ge_rx_done(struct myri10ge_slice_state *ss, struct myri10ge_rx_buf *rx,
remainder -= MYRI10GE_ALLOC_SIZE;
}
if (dev->features & NETIF_F_LRO) {
if (lro_enabled) {
rx_frags[0].page_offset += MXGEFW_PAD;
rx_frags[0].size -= MXGEFW_PAD;
len -= MXGEFW_PAD;
@ -1463,7 +1472,7 @@ myri10ge_clean_rx_done(struct myri10ge_slice_state *ss, int budget)
{
struct myri10ge_rx_done *rx_done = &ss->rx_done;
struct myri10ge_priv *mgp = ss->mgp;
struct net_device *netdev = mgp->dev;
unsigned long rx_bytes = 0;
unsigned long rx_packets = 0;
unsigned long rx_ok;
@ -1474,18 +1483,18 @@ myri10ge_clean_rx_done(struct myri10ge_slice_state *ss, int budget)
u16 length;
__wsum checksum;
/*
* Prevent compiler from generating more than one ->features memory
* access to avoid theoretical race condition with functions that
* change NETIF_F_LRO flag at runtime.
*/
bool lro_enabled = ACCESS_ONCE(mgp->dev->features) & NETIF_F_LRO;
while (rx_done->entry[idx].length != 0 && work_done < budget) {
length = ntohs(rx_done->entry[idx].length);
rx_done->entry[idx].length = 0;
checksum = csum_unfold(rx_done->entry[idx].checksum);
if (length <= mgp->small_bytes)
rx_ok = myri10ge_rx_done(ss, &ss->rx_small,
mgp->small_bytes,
length, checksum);
else
rx_ok = myri10ge_rx_done(ss, &ss->rx_big,
mgp->big_bytes,
length, checksum);
rx_ok = myri10ge_rx_done(ss, length, checksum, lro_enabled);
rx_packets += rx_ok;
rx_bytes += rx_ok * (unsigned long)length;
cnt++;
@ -1497,7 +1506,7 @@ myri10ge_clean_rx_done(struct myri10ge_slice_state *ss, int budget)
ss->stats.rx_packets += rx_packets;
ss->stats.rx_bytes += rx_bytes;
if (netdev->features & NETIF_F_LRO)
if (lro_enabled)
lro_flush_all(&rx_done->lro_mgr);
/* restock receive rings if needed */