Commit Graph

5578 Commits

Author SHA1 Message Date
David S. Miller f6d3125fa3 Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net
Conflicts:
	net/dsa/slave.c

net/dsa/slave.c simply had overlapping changes.

Signed-off-by: David S. Miller <davem@davemloft.net>
2015-10-02 07:21:25 -07:00
Dirk Müller 038161dea1 Update KVM homepage Url
The old one appears to be a generic catch all page, which
is unhelpful.

Signed-off-by: Dirk Mueller <dmueller@suse.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2015-10-01 14:31:26 +02:00
David Ahern ec539514e5 net: Remove vrf header file
Move remaining structs to VRF driver and delete the vrf header file.

Signed-off-by: David Ahern <dsa@cumulusnetworks.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2015-09-29 20:40:33 -07:00
David Ahern 1b69c6d0ae net: Introduce L3 Master device abstraction
L3 master devices allow users of the abstraction to influence FIB lookups
for enslaved devices. Current API provides a means for the master device
to return a specific FIB table for an enslaved device, to return an
rtable/custom dst and influence the OIF used for fib lookups.

Signed-off-by: David Ahern <dsa@cumulusnetworks.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2015-09-29 20:40:32 -07:00
Linus Torvalds bcba282ab3 Merge tag 'usb-4.3-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb
Pull USB fixes from Greg KH:
 "Here are some USB driver fixes for 4.3-rc3.

  There's the usual assortment of new device ids, combined with xhci and
  gadget driver fixes.  Full details in the shortlog.  All of these have
  been in linux-next with no reported problems"

* tag 'usb-4.3-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb: (34 commits)
  MAINTAINERS: remove amd5536udc USB gadget driver maintainer
  USB: whiteheat: fix potential null-deref at probe
  xhci: init command timeout timer earlier to avoid deleting it uninitialized
  xhci: change xhci 1.0 only restrictions to support xhci 1.1
  usb: xhci: exit early in xhci_setup_device() if we're halted or dying
  usb: xhci: stop everything on the first call to xhci_stop
  usb: xhci: Clear XHCI_STATE_DYING on start
  usb: xhci: lock mutex on xhci_stop
  xhci: Move xhci_pme_quirk() behind #ifdef CONFIG_PM
  xhci: give command abortion one more chance before killing xhci
  usb: Use the USB_SS_MULT() macro to get the burst multiplier.
  usb: dwc3: gadget: Fix BUG in RT config
  usb: musb: fix cppi channel teardown for isoch transfer
  usb: phy: isp1301: Export I2C module alias information
  usb: gadget: drop null test before destroy functions
  usb: gadget: dummy_hcd: in transfer(), return data sent, not limit
  usb: gadget: dummy_hcd: fix rescan logic for transfer
  usb: gadget: dummy_hcd: fix unneeded else-if condition
  usb: gadget: dummy_hcd: emulate sending zlp in packet logic
  usb: musb: dsps: fix polling in device-only mode
  ...
2015-09-26 21:00:28 -04:00
Linus Torvalds b11e7b81bf Merge tag 'staging-4.3-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/staging
Pull staging driver fixes from Greg KH:
 "Here are some tiny staging driver and documentation fixes for 4.3-rc3.

  All of these resolve reported issues that people have found and have
  been in the linux-next tree for a while with no problems"

* tag 'staging-4.3-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/staging:
  MAINTAINERS: Update email address for Martyn Welch
  staging: ion: fix corruption of ion_import_dma_buf
  staging: dgap: Remove myself from the MAINTAINERS file
  staging: most: Add dependency to HAS_IOMEM
  staging: unisys: remove reference of visorutil
  staging: unisys: visornic: handle error return from device registration
  staging: unisys: stop device registration before visorbus registration
  staging: unisys: visorbus: Unregister driver on error
  staging: unisys: visornic: Fix receive bytes statistics
  staging: unisys: unregister netdev when create debugfs fails
  staging: fbtft: replace master->setup() with spi_setup()
  staging: fbtft: fix 9-bit SPI support detection
  staging/lustre: change Lustre URLs and mailing list
  staging/android: Update ION TODO per LPC discussion
  Staging: most: MOST and MOSTCORE should depend on HAS_DMA
  staging: most: fix HDM_USB dependencies and build errors
2015-09-26 20:56:50 -04:00
David S. Miller 4963ed48f2 Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net
Conflicts:
	net/ipv4/arp.c

The net/ipv4/arp.c conflict was one commit adding a new
local variable while another commit was deleting one.

Signed-off-by: David S. Miller <davem@davemloft.net>
2015-09-26 16:08:27 -07:00
Linus Torvalds 518a7cb698 Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net
Pull networking fixes from David Miller:

 1) When we run a tap on netlink sockets, we have to copy mmap'd SKBs
    instead of cloning them.  From Daniel Borkmann.

 2) When converting classical BPF into eBPF, fix the setting of the
    source reg to BPF_REG_X.  From Tycho Andersen.

 3) Fix igmpv3/mldv2 report parsing in the bridge multicast code, from
    Linus Lussing.

 4) Fix dst refcounting for ipv6 tunnels, from Martin KaFai Lau.

 5) Set NLM_F_REPLACE flag properly when replacing ipv6 routes, from
    Roopa Prabhu.

 6) Add some new cxgb4 PCI device IDs, from Hariprasad Shenai.

 7) Fix headroom tests and SKB leaks in ipv6 fragmentation code, from
    Florian Westphal.

 8) Check DMA mapping errors in bna driver, from Ivan Vecera.

 9) Several 8139cp bug fixes (dev_kfree_skb_any in interrupt context,
    misclearing of interrupt status in TX timeout handler, etc.) from
    David Woodhouse.

10) In tipc, reset SKB header pointer after skb_linearize(), from Erik
    Hugne.

11) Fix autobind races et al. in netlink code, from Herbert Xu with
    help from Tejun Heo and others.

12) Missing SET_NETDEV_DEV in sunvnet driver, from Sowmini Varadhan.

13) Fix various races in timewait timer and reqsk_queue_hadh_req, from
    Eric Dumazet.

14) Fix array overruns in mac80211, from Johannes Berg and Dan
    Carpenter.

15) Fix data race in rhashtable_rehash_one(), from Dmitriy Vyukov.

16) Fix race between poll_one_napi and napi_disable, from Neil Horman.

17) Fix byte order in geneve tunnel port config, from John W Linville.

18) Fix handling of ARP replies over lightweight tunnels, from Jiri
    Benc.

19) We can loop when fib rule dumps cross multiple SKBs, fix from Wilson
    Kok and Roopa Prabhu.

20) Several reference count handling bug fixes in the PHY/MDIO layer
    from Russel King.

21) Fix lockdep splat in ppp_dev_uninit(), from Guillaume Nault.

22) Fix crash in icmp_route_lookup(), from David Ahern.

* git://git.kernel.org/pub/scm/linux/kernel/git/davem/net: (116 commits)
  net: Fix panic in icmp_route_lookup
  net: update docbook comment for __mdiobus_register()
  ppp: fix lockdep splat in ppp_dev_uninit()
  net: via/Kconfig: GENERIC_PCI_IOMAP required if PCI not selected
  phy: marvell: add link partner advertised modes
  net: fix net_device refcounting
  phy: add phy_device_remove()
  phy: fixed-phy: properly validate phy in fixed_phy_update_state()
  net: fix phy refcounting in a bunch of drivers
  of_mdio: fix MDIO phy device refcounting
  phy: add proper phy struct device refcounting
  phy: fix mdiobus module safety
  net: dsa: fix of_mdio_find_bus() device refcount leak
  phy: fix of_mdio_find_bus() device refcount leak
  ip6_tunnel: Reduce log level in ip6_tnl_err() to debug
  ip6_gre: Reduce log level in ip6gre_err() to debug
  fib_rules: fix fib rule dumps across multiple skbs
  bnx2x: byte swap rss_key to comply to Toeplitz specs
  net: revert "net_sched: move tp->root allocation into fw_init()"
  lwtunnel: remove source and destination UDP port config option
  ...
2015-09-26 06:01:33 -04:00
Greg Kroah-Hartman b473197724 MAINTAINERS: remove amd5536udc USB gadget driver maintainer
Thomas can no longer work on the driver, so he asked me to mark the
MAINTAINER entry as "Orphan" with the hope that someone else would
someday pick it up.

Cc: Thomas Dahlmann <dahlmann.thomas@arcor.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2015-09-25 20:45:27 -07:00
Linus Torvalds ddff42e592 Merge tag 'sound-4.3-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/tiwai/sound
Pull sound fixes from Takashi Iwai:
 "This ended up with a larger set of fixes than wished, unfortunately.

  As diffstat shows, the majority of changes are for various ASoC
  drivers (Realtek, Wolfson codec drivers, etc), in addition to a couple
  of HD-audio regression fixes.  All these are reasonably small and
  nothing to scare much"

* tag 'sound-4.3-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/tiwai/sound: (29 commits)
  ALSA: hda - Disable power_save_node for Thinkpads
  ALSA: hda/tegra - async probe for avoiding module loading deadlock
  ASoC: rt5645: Prevent the pop sound in case of playback and the jack is plugging
  ASoC: rt5645: Increase the delay time to remove the pop sound
  ASoC: rt5645: Use the type SOC_DAPM_SINGLE_AUTODISABLE to prevent the weird sound in runtime of power up
  ASoC: pxa: pxa2xx-ac97: fix dma requestor lines
  MAINTAINERS: Update website and git repo for Wolfson Microelectronics
  ASoC: fsl_ssi: Fix checking of dai format for AC97 mode
  ASoC: wm0010: fix error path
  ASoC: wm0010: fix memory leak
  ASoC: wm8960: correct the max register value of mic boost pga
  ASoC: wm8962: remove 64k sample rate support
  ASoC: davinci-mcasp: Fix devm_kasprintf format string
  ASoC: fix broken pxa SoC support
  ASoC: davinci-mcasp: Set .symmetric_rates = 1 in snd_soc_dai_driver
  ASoC: au1x: psc-i2s: Fix unused variable 'ret' warning
  ASoC: SPEAr: Make SND_SPEAR_SOC select SND_SOC_GENERIC_DMAENGINE_PCM
  ASoC: mediatek: Increase periods_min in capture
  ASoC: davinci-mcasp: Revise the FIFO threshold calculation
  ASoC: wm8960: correct gain value for input PGA and add microphone PGA
  ...
2015-09-25 11:25:30 -07:00
Linus Torvalds ced255c0c5 Merge branch 'next' of git://git.kernel.org/pub/scm/linux/kernel/git/rzhang/linux
Pull thermal management fixes from Zhang Rui:

 - Power allocator governor changes to allow binding on thermal zones
   with missing power estimates information.  From Javi Merino.

 - Add compile test flags on thermal drivers that allow it without
   producing compilation errors.  From Eduardo Valentin.

 - Fixes around memory allocation on cpu_cooling.  From Javi Merino.

 - Fix on db8500 cpufreq code to allow autoload.  From Luis de
   Bethencourt.

 - Maintainer entries for cpu cooling device

* 'next' of git://git.kernel.org/pub/scm/linux/kernel/git/rzhang/linux:
  thermal: power_allocator: exit early if there are no cooling devices
  thermal: power_allocator: don't require tzp to be present for the thermal zone
  thermal: power_allocator: relax the requirement of two passive trip points
  thermal: power_allocator: relax the requirement of a sustainable_power in tzp
  thermal: Add a function to get the minimum power
  thermal: cpu_cooling: free power table on error or when unregistering
  thermal: cpu_cooling: don't call kcalloc() under rcu_read_lock
  thermal: db8500_cpufreq_cooling: Fix module autoload for OF platform driver
  thermal: cpu_cooling: Add MAINTAINERS entry
  thermal: ti-soc: Kconfig fix to avoid menu showing wrongly
  thermal: ti-soc: allow compile test
  thermal: qcom_spmi: allow compile test
  thermal: exynos: allow compile test
  thermal: armada: allow compile test
  thermal: dove: allow compile test
  thermal: kirkwood: allow compile test
  thermal: rockchip: allow compile test
  thermal: spear: allow compile test
  thermal: hisi: allow compile test
  thermal: Fix thermal_zone_of_sensor_register to match documentation
2015-09-24 20:14:26 -07:00
Mark Brown 312e0bce7f Merge remote-tracking branches 'asoc/fix/davinci', 'asoc/fix/doc', 'asoc/fix/fsl-card', 'asoc/fix/fsl-ssi', 'asoc/fix/intel' and 'asoc/fix/maintainers' into asoc-linus 2015-09-23 11:01:03 -07:00
Joe Perches 26c6d28168 arcnet: Move files out of include/linux
These #include files don't need to be in the include/linux directory
as they can be local to drivers/net/arcnet/

Move them and update the #include statements.

Update the MAINTAINERS file pattern by deleting arcdevice from the
NETWORKING block as arcnet is currently unmaintained.

Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: Michael Grzeschik <m.grzeschik@pengutronix.de>
2015-09-23 08:44:25 +02:00
Richard Fitzgerald f0e03dbd2d MAINTAINERS: Update website and git repo for Wolfson Microelectronics
Support for Wolfson Microelectronics devices is now part of Cirrus Logic
and the relevant parts of the old opensource.wolfsonmicro.com site have
moved to the Cirrus Logic GitHub area.

This patch updates the website and git repo links, and also removes an
obsolete website link for the voltage and current drivers.

Signed-off-by: Richard Fitzgerald <rf@opensource.wolfsonmicro.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
2015-09-22 09:33:16 -07:00
Jiri Benc 6cf3564214 MAINTAINERS: remove bouncing email address for qlcnic
I got this automated message from <shahed.shaikh@qlogic.com> when submitting
a qlcnic patch:

> Shahed Shaikh is no longer with QLogic. If you require assistance please
> contact Ariel Elior Ariel.Elior@qlogic.com

There's no point in having a bouncing address in MAINTAINERS.

CC: Dept-GELinuxNICDev@qlogic.com
CC: Ariel Elior <Ariel.Elior@qlogic.com>
Signed-off-by: Jiri Benc <jbenc@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2015-09-17 22:33:24 -07:00
Michael Grzeschik c38f6ac74c MAINTAINERS: add arcnet and take maintainership
Add entry for arcnet to MAINTAINERS file and add myself as the
maintainer of the subsystem.

Signed-off-by: Michael Grzeschik <m.grzeschik@pengutronix.de>
Cc: davem@davemloft.net
Cc: joe@perches.com
Signed-off-by: David S. Miller <davem@davemloft.net>
2015-09-17 22:26:55 -07:00
Cyril Hrubis 0526109a24 MAINTAINERS: update LTP mailing list
[akpm@linux-foundation.org: Wanlong Gao has moved]
Signed-off-by: Cyril Hrubis <chrubis@suse.cz>
Cc: Jan Stancek <jstancek@redhat.com>
Cc: Stanislav Kholmanskikh <stanislav.kholmanskikh@oracle.com>
Cc: Alexey Kodanev <alexey.kodanev@oracle.com>
Cc: Wanlong Gao <wanlong.gao@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-09-17 21:16:07 -07:00
David Ahern 562d897d15 net: Add documentation for VRF device
Signed-off-by: David Ahern <dsa@cumulusnetworks.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2015-09-17 16:06:43 -07:00
Martyn Welch 74c600e364 MAINTAINERS: Update email address for Martyn Welch
I have recently left GE and the email address listed for me in the
maintainers file is no longer valid. Updating email address.

Signed-off-by: Martyn Welch <martyn@welchs.me.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2015-09-17 14:27:37 -07:00
Mark Hounschell 989e503c92 staging: dgap: Remove myself from the MAINTAINERS file
Removes myself from the MAINTAINERS file for the dgap driver.
There appears to be no way to get the firmware files required
by the dgap driver into the linux-firmware tree. The dgap
driver is useless wihtout this firmware. This product is
considered an obsolete product by Digi. They will not respond
to an inquiry concerning it or its firmware.

Signed-off-by: Mark Hounschell <markh@compro.net>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2015-09-17 06:11:03 -07:00
Viresh Kumar 64e05d8bcc thermal: cpu_cooling: Add MAINTAINERS entry
None of the patches are reaching Viresh or Daniel directly as
get_maintainers doesn't report us as maintainers. Looks like file header
or history of commits isn't able to do that properly.

Add a separate entry for cpu_cooling driver in MAINTAINERS.

Acked-by: Eduardo Valentin <edubezval@gmail.com>
Acked-by: Amit Daniel Kachhap <amit.daniel@samsung.com>
Acked-by: Amit Daniel Kachhap <amit.kachhap@gmail.com>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Eduardo Valentin <edubezval@gmail.com>
2015-09-13 20:05:53 -07:00
Andreas Dilger d98229f029 staging/lustre: change Lustre URLs and mailing list
Now that the lustre.org domain has been liberated we can again
use that for the main website URL and mailing list.

Also update the URL for userspace tools downloads and Git repo.

Signed-off-by: Andreas Dilger <andreas.dilger@intel.com>
Signed-off-by: Oleg Drokin <oleg.drokin@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2015-09-13 09:28:27 -07:00
Linus Torvalds 01b0c014ee Merge branch 'akpm' (patches from Andrew)
Merge fourth patch-bomb from Andrew Morton:

 - sys_membarier syscall

 - seq_file interface changes

 - a few misc fixups

* emailed patches from Andrew Morton <akpm@linux-foundation.org>:
  revert "ocfs2/dlm: use list_for_each_entry instead of list_for_each"
  mm/early_ioremap: add explicit #include of asm/early_ioremap.h
  fs/seq_file: convert int seq_vprint/seq_printf/etc... returns to void
  selftests: enhance membarrier syscall test
  selftests: add membarrier syscall test
  sys_membarrier(): system-wide memory barrier (generic, x86)
  MODSIGN: fix a compilation warning in extract-cert
2015-09-11 19:34:09 -07:00
Linus Torvalds ded0e250b5 Merge tag 'ntb-4.3' of git://github.com/jonmason/ntb
Pull NTB fixes from Jon Mason:
 "NTB bug and documentation fixes, new device IDs, performance
  improvements, and adding a mailing list to MAINTAINERS for NTB"

* tag 'ntb-4.3' of git://github.com/jonmason/ntb:
  NTB: Fix range check on memory window index
  NTB: Improve index handling in B2B MW workaround
  NTB: Fix documentation for ntb_peer_db_clear.
  NTB: Fix documentation for ntb_link_is_up
  NTB: Use unique DMA channels for TX and RX
  NTB: Remove dma_sync_wait from ntb_async_rx
  NTB: Clean up QP stats info
  NTB: Make the transport list in order of discovery
  NTB: Add PCI Device IDs for Broadwell Xeon
  NTB: Add flow control to the ntb_netdev
  NTB: Add list to MAINTAINERS
2015-09-11 19:29:00 -07:00
Mathieu Desnoyers 5b25b13ab0 sys_membarrier(): system-wide memory barrier (generic, x86)
Here is an implementation of a new system call, sys_membarrier(), which
executes a memory barrier on all threads running on the system.  It is
implemented by calling synchronize_sched().  It can be used to
distribute the cost of user-space memory barriers asymmetrically by
transforming pairs of memory barriers into pairs consisting of
sys_membarrier() and a compiler barrier.  For synchronization primitives
that distinguish between read-side and write-side (e.g.  userspace RCU
[1], rwlocks), the read-side can be accelerated significantly by moving
the bulk of the memory barrier overhead to the write-side.

The existing applications of which I am aware that would be improved by
this system call are as follows:

* Through Userspace RCU library (http://urcu.so)
  - DNS server (Knot DNS) https://www.knot-dns.cz/
  - Network sniffer (http://netsniff-ng.org/)
  - Distributed object storage (https://sheepdog.github.io/sheepdog/)
  - User-space tracing (http://lttng.org)
  - Network storage system (https://www.gluster.org/)
  - Virtual routers (https://events.linuxfoundation.org/sites/events/files/slides/DPDK_RCU_0MQ.pdf)
  - Financial software (https://lkml.org/lkml/2015/3/23/189)

Those projects use RCU in userspace to increase read-side speed and
scalability compared to locking.  Especially in the case of RCU used by
libraries, sys_membarrier can speed up the read-side by moving the bulk of
the memory barrier cost to synchronize_rcu().

* Direct users of sys_membarrier
  - core dotnet garbage collector (https://github.com/dotnet/coreclr/issues/198)

Microsoft core dotnet GC developers are planning to use the mprotect()
side-effect of issuing memory barriers through IPIs as a way to implement
Windows FlushProcessWriteBuffers() on Linux.  They are referring to
sys_membarrier in their github thread, specifically stating that
sys_membarrier() is what they are looking for.

To explain the benefit of this scheme, let's introduce two example threads:

Thread A (non-frequent, e.g. executing liburcu synchronize_rcu())
Thread B (frequent, e.g. executing liburcu
rcu_read_lock()/rcu_read_unlock())

In a scheme where all smp_mb() in thread A are ordering memory accesses
with respect to smp_mb() present in Thread B, we can change each
smp_mb() within Thread A into calls to sys_membarrier() and each
smp_mb() within Thread B into compiler barriers "barrier()".

Before the change, we had, for each smp_mb() pairs:

Thread A                    Thread B
previous mem accesses       previous mem accesses
smp_mb()                    smp_mb()
following mem accesses      following mem accesses

After the change, these pairs become:

Thread A                    Thread B
prev mem accesses           prev mem accesses
sys_membarrier()            barrier()
follow mem accesses         follow mem accesses

As we can see, there are two possible scenarios: either Thread B memory
accesses do not happen concurrently with Thread A accesses (1), or they
do (2).

1) Non-concurrent Thread A vs Thread B accesses:

Thread A                    Thread B
prev mem accesses
sys_membarrier()
follow mem accesses
                            prev mem accesses
                            barrier()
                            follow mem accesses

In this case, thread B accesses will be weakly ordered. This is OK,
because at that point, thread A is not particularly interested in
ordering them with respect to its own accesses.

2) Concurrent Thread A vs Thread B accesses

Thread A                    Thread B
prev mem accesses           prev mem accesses
sys_membarrier()            barrier()
follow mem accesses         follow mem accesses

In this case, thread B accesses, which are ensured to be in program
order thanks to the compiler barrier, will be "upgraded" to full
smp_mb() by synchronize_sched().

* Benchmarks

On Intel Xeon E5405 (8 cores)
(one thread is calling sys_membarrier, the other 7 threads are busy
looping)

1000 non-expedited sys_membarrier calls in 33s =3D 33 milliseconds/call.

* User-space user of this system call: Userspace RCU library

Both the signal-based and the sys_membarrier userspace RCU schemes
permit us to remove the memory barrier from the userspace RCU
rcu_read_lock() and rcu_read_unlock() primitives, thus significantly
accelerating them. These memory barriers are replaced by compiler
barriers on the read-side, and all matching memory barriers on the
write-side are turned into an invocation of a memory barrier on all
active threads in the process. By letting the kernel perform this
synchronization rather than dumbly sending a signal to every process
threads (as we currently do), we diminish the number of unnecessary wake
ups and only issue the memory barriers on active threads. Non-running
threads do not need to execute such barrier anyway, because these are
implied by the scheduler context switches.

Results in liburcu:

Operations in 10s, 6 readers, 2 writers:

memory barriers in reader:    1701557485 reads, 2202847 writes
signal-based scheme:          9830061167 reads,    6700 writes
sys_membarrier:               9952759104 reads,     425 writes
sys_membarrier (dyn. check):  7970328887 reads,     425 writes

The dynamic sys_membarrier availability check adds some overhead to
the read-side compared to the signal-based scheme, but besides that,
sys_membarrier slightly outperforms the signal-based scheme. However,
this non-expedited sys_membarrier implementation has a much slower grace
period than signal and memory barrier schemes.

Besides diminishing the number of wake-ups, one major advantage of the
membarrier system call over the signal-based scheme is that it does not
need to reserve a signal. This plays much more nicely with libraries,
and with processes injected into for tracing purposes, for which we
cannot expect that signals will be unused by the application.

An expedited version of this system call can be added later on to speed
up the grace period. Its implementation will likely depend on reading
the cpu_curr()->mm without holding each CPU's rq lock.

This patch adds the system call to x86 and to asm-generic.

[1] http://urcu.so

membarrier(2) man page:

MEMBARRIER(2)              Linux Programmer's Manual             MEMBARRIER(2)

NAME
       membarrier - issue memory barriers on a set of threads

SYNOPSIS
       #include <linux/membarrier.h>

       int membarrier(int cmd, int flags);

DESCRIPTION
       The cmd argument is one of the following:

       MEMBARRIER_CMD_QUERY
              Query  the  set  of  supported commands. It returns a bitmask of
              supported commands.

       MEMBARRIER_CMD_SHARED
              Execute a memory barrier on all threads running on  the  system.
              Upon  return from system call, the caller thread is ensured that
              all running threads have passed through a state where all memory
              accesses  to  user-space  addresses  match program order between
              entry to and return from the system  call  (non-running  threads
              are de facto in such a state). This covers threads from all pro=E2=80=90
              cesses running on the system.  This command returns 0.

       The flags argument needs to be 0. For future extensions.

       All memory accesses performed  in  program  order  from  each  targeted
       thread is guaranteed to be ordered with respect to sys_membarrier(). If
       we use the semantic "barrier()" to represent a compiler barrier forcing
       memory  accesses  to  be performed in program order across the barrier,
       and smp_mb() to represent explicit memory barriers forcing full  memory
       ordering  across  the barrier, we have the following ordering table for
       each pair of barrier(), sys_membarrier() and smp_mb():

       The pair ordering is detailed as (O: ordered, X: not ordered):

                              barrier()   smp_mb() sys_membarrier()
              barrier()          X           X            O
              smp_mb()           X           O            O
              sys_membarrier()   O           O            O

RETURN VALUE
       On success, these system calls return zero.  On error, -1 is  returned,
       and errno is set appropriately. For a given command, with flags
       argument set to 0, this system call is guaranteed to always return the
       same value until reboot.

ERRORS
       ENOSYS System call is not implemented.

       EINVAL Invalid arguments.

Linux                             2015-04-15                     MEMBARRIER(2)

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Reviewed-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Nicholas Miell <nmiell@comcast.net>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Alan Cox <gnomes@lxorguk.ukuu.org.uk>
Cc: Lai Jiangshan <laijs@cn.fujitsu.com>
Cc: Stephen Hemminger <stephen@networkplumber.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: David Howells <dhowells@redhat.com>
Cc: Pranith Kumar <bobby.prani@gmail.com>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Cc: Shuah Khan <shuahkh@osg.samsung.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-09-11 15:21:34 -07:00