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11848b9647
linux-next/drivers
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Michael Chan 11848b9647 bnx2: Remove some unnecessary smp_mb() in tx fast path. 
smp_mb() inside bnx2_tx_avail() is used twice in the normal
bnx2_start_xmit() path (see illustration below).  The full memory
barrier is only necessary during race conditions with tx completion.
We can speed up the tx path by replacing smp_mb() in bnx2_tx_avail()
with a compiler barrier.  The compiler barrier is to force the
compiler to fetch the tx_prod and tx_cons from memory.

In the race condition between bnx2_start_xmit() and bnx2_tx_int(),
we have the following situation:

bnx2_start_xmit()                       bnx2_tx_int()
    if (!bnx2_tx_avail())
            BUG();

    ...

    if (!bnx2_tx_avail())
            netif_tx_stop_queue();          update_tx_index();
            smp_mb();                       smp_mb();
            if (bnx2_tx_avail())            if (netif_tx_queue_stopped() &&
                    netif_tx_wake_queue();      bnx2_tx_avail())

With smp_mb() removed from bnx2_tx_avail(), we need to add smp_mb() to
bnx2_start_xmit() as shown above to properly order netif_tx_stop_queue()
and bnx2_tx_avail() to check the ring index.  If it is not strictly
ordered, the tx queue can be stopped forever.

This improves performance by about 5% with 2 ports running bi-directional
64-byte packets.

Reviewed-by: Benjamin Li <benli@broadcom.com>
Reviewed-by: Matt Carlson <mcarlson@broadcom.com>
Signed-off-by: Michael Chan <mchan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2010-07-19 20:30:06 -07:00
..
accessibility
acpi Merge branch 'idle-release' of git://git.kernel.org/pub/scm/linux/kernel/git/lenb/linux-idle-2.6 2010-05-28 16:14:17 -07:00
amba
ata libata: implement dump_id force param 2010-05-25 19:41:19 -04:00
atm atm: Convert pci_table entries to PCI_VDEVICE (if PCI_ANY_ID is used) 2010-07-15 19:05:21 -07:00
auxdisplay auxdisplay: section cleanup in cfag12864bfb driver 2010-05-25 08:07:09 -07:00
base device.h drivers/base/core.c Convert dev_<level> logging macros to functions 2010-07-04 10:40:17 -07:00
block Merge remote branch 'origin' into secretlab/next-devicetree 2010-05-22 00:36:56 -06:00
bluetooth drivers: bluetooth: bluecard_cs.c: Fixed include error, changed to linux/io.h 2010-07-01 21:28:14 -07:00
cdrom of: Always use 'struct device.of_node' to get device node pointer. 2010-05-18 16:10:44 -06:00
char drop unused dentry argument to ->fsync 2010-05-27 22:05:02 -04:00
clocksource Merge branch 'timers-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip 2010-05-19 17:10:57 -07:00
connector
cpufreq Merge branch 'x86-cpu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip 2010-05-18 08:49:13 -07:00
cpuidle Merge branch 'idle-release' of git://git.kernel.org/pub/scm/linux/kernel/git/lenb/linux-idle-2.6 2010-05-28 16:14:17 -07:00
crypto Merge remote branch 'origin' into secretlab/next-devicetree 2010-05-22 00:36:56 -06:00
dca
dio
dma Merge branch 'next' of git://git.kernel.org/pub/scm/linux/kernel/git/djbw/async_tx 2010-05-30 09:12:43 -07:00
edac drivers/edac: convert logging messages direct uses of __FILE__ to %s, __FILE 2010-05-27 09:12:52 -07:00
eisa
firewire Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ieee1394/linux1394-2.6 2010-05-27 10:22:06 -07:00
firmware sysfs: add struct file* to bin_attr callbacks 2010-05-21 09:37:31 -07:00
gpio gpio: Fix inverted rdc321x gpio data out registers 2010-05-28 01:37:59 +02:00
gpu Merge branch 'drm-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/airlied/drm-2.6 2010-05-28 16:14:40 -07:00
hid Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/dtor/input 2010-05-27 09:19:55 -07:00
hwmon hwmon: (lm75) Add support for the Texas Instruments TMP105 2010-05-27 19:59:03 +02:00
i2c Merge remote branch 'origin' into secretlab/next-devicetree 2010-05-22 00:36:56 -06:00
ide m68k: amiga - Amiga Gayle IDE platform device conversion 2010-05-26 19:51:09 +02:00
idle intel_idle: native hardware cpuidle driver for latest Intel processors 2010-05-28 14:26:20 -04:00
ieee1394 Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ieee1394/linux1394-2.6 2010-05-27 10:22:06 -07:00
ieee802154
infiniband IB/{nes, ipoib}: Pass supported flags to ethtool_op_set_flags() 2010-07-04 11:48:14 -07:00
input input: Touchscreen driver for TPS6507x 2010-05-28 01:37:38 +02:00
isdn drivers: isdn: get rid of custom strtoul() 2010-07-15 19:05:25 -07:00
leds leds: Fix leds-gpio openfirmware compile issue 2010-05-28 08:35:27 +01:00
lguest
macintosh Merge branch 'bkl/ioctl' of git://git.kernel.org/pub/scm/linux/kernel/git/frederic/random-tracing 2010-05-24 08:01:10 -07:00
mca
md md: convert cpu notifier to return encapsulate errno value 2010-05-27 09:12:48 -07:00
media Merge branch 'bkl/ioctl' of git://git.kernel.org/pub/scm/linux/kernel/git/frederic/random-tracing 2010-05-24 08:01:10 -07:00
memstick
message drivers/message/i2o/i2o_config.c: use memdup_user 2010-05-27 09:12:41 -07:00
mfd mfd: Rename twl5031 sih modules 2010-05-28 01:38:02 +02:00
misc lktdm: add support for hardlockup, softlockup and hung task crashes 2010-05-27 09:12:54 -07:00
mmc drivers/mmc/host: use ERR_CAST 2010-05-27 09:12:40 -07:00
mtd drop unused dentry argument to ->fsync 2010-05-27 22:05:02 -04:00
net bnx2: Remove some unnecessary smp_mb() in tx fast path. 2010-07-19 20:30:06 -07:00
nubus
of Merge remote branch 'origin' into secretlab/next-devicetree 2010-05-22 00:36:56 -06:00
oprofile
parisc net: fix 64 bit counters on 32 bit arches 2010-07-07 14:58:56 -07:00
parport m68k: amiga - Parallel port platform device conversion 2010-05-26 19:51:09 +02:00
pci Merge branch 'release' of git://git.kernel.org/pub/scm/linux/kernel/git/lenb/linux-acpi-2.6 2010-05-28 14:42:18 -07:00
pcmcia Merge branch 'bkl/ioctl' of git://git.kernel.org/pub/scm/linux/kernel/git/frederic/random-tracing 2010-05-24 08:01:10 -07:00
platform Move N014, N051 and CR620 dmi information to load scm dmi table 2010-05-20 10:16:13 -04:00
pnp
power Merge git://git.infradead.org/battery-2.6 2010-05-25 08:16:34 -07:00
pps
ps3
rapidio rapidio: fix new kernel-doc warnings 2010-05-30 09:02:47 -07:00
regulator mfd: AB3100 register access change to abx500 API 2010-05-28 01:37:45 +02:00
rtc mfd: AB3100 register access change to abx500 API 2010-05-28 01:37:45 +02:00
s390 qeth: handle missing z/VM authorization of OSX 2010-06-23 13:16:37 -07:00
sbus Merge branch 'bkl/ioctl' of git://git.kernel.org/pub/scm/linux/kernel/git/frederic/random-tracing 2010-05-24 08:01:10 -07:00
scsi net: fix 64 bit counters on 32 bit arches 2010-07-07 14:58:56 -07:00
serial pcnet_cs: add new id (TOSHIBA Modem/LAN Card) 2010-06-16 18:10:54 -07:00
sfi SFI: add sysfs interface for SFI tables. 2010-05-27 12:46:20 -04:00
sh sh: simplify WARN usage in SH clock driver 2010-05-13 17:43:11 +09:00
sn
spi spi/xilinx: Fix compile error 2010-05-25 00:48:24 -06:00
ssb ssb: remove the ssb DMA API 2010-06-04 16:00:42 -04:00
staging net: preserve ifreq parameter when calling generic phy_mii_ioctl(). 2010-07-18 19:15:25 -07:00
tc
telephony drivers/telephony/ixj.c: use memdup_user 2010-05-27 09:12:42 -07:00
thermal
uio
usb usb/atm/ueagle-atm.c: call atm_dev_signal_change() when signal changes. 2010-07-09 00:09:24 -07:00
uwb
vhost Merge branch 'master' of master.kernel.org:/pub/scm/linux/kernel/git/davem/net-2.6 2010-07-07 15:59:38 -07:00
video drop unused dentry argument to ->fsync 2010-05-27 22:05:02 -04:00
virtio Merge branch 'virtio' of git://git.kernel.org/pub/scm/linux/kernel/git/rusty/linux-2.6-for-linus 2010-05-21 17:22:52 -07:00
vlynq vlynq: make whole Kconfig-menu dependant on architecture 2010-05-14 16:59:54 +02:00
w1 sysfs: add struct file* to bin_attr callbacks 2010-05-21 09:37:31 -07:00
watchdog mfd: Change rdc321x resources flags to IORESOURCE_IO 2010-05-28 01:37:52 +02:00
xen xen: fix build when SYSRQ is disabled 2010-05-25 08:07:07 -07:00
zorro sysfs: add struct file* to bin_attr callbacks 2010-05-21 09:37:31 -07:00
Kconfig
Makefile intel_idle: native hardware cpuidle driver for latest Intel processors 2010-05-28 14:26:20 -04:00