Because the adaptive synchronize_srcu_expedited() approach has
worked very well in testing, remove the kernel parameter and
replace it by a C-preprocessor macro.  If someone finds problems
with this approach, a more complex and aggressively adaptive
approach might be required.

Longer term, SRCU will be merged with the other RCU implementations,
at which point synchronize_srcu_expedited() will be event driven,
just as synchronize_sched_expedited() currently is.  At that point,
there will be no need for this adaptive approach.
Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

Merge branch 'rcu/next' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-2.6-rcu into core/rcu

* 'tty-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty-2.6:
  n_gsm: gsm_data_alloc buffer allocation could fail and it is not being checked
  n_gsm: Fix message length handling when building header

* 'usb-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb-2.6:
  Revert "USB: gadget: Allow function access to device ID data during bind()"
  USB: misc: uss720.c: add another vendor/product ID
  USB: usb-storage: unusual_devs entry for the Samsung YP-CP3
  USB: gadget: Remove suspended sysfs file before freeing cdev
  USB: core: Add input prompt and help text for USB_OTG config
  USB: ftdi_sio: Add D.O.Tec PID
  xhci: Fix issue with port array setup and buggy hosts.

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/sage/ceph-client:
  ceph: handle partial result from get_user_pages
  ceph: mark user pages dirty on direct-io reads
  ceph: fix null pointer dereference in ceph_init_dentry for nfs reexport
  ceph: fix direct-io on non-page-aligned buffers
  ceph: fix msgr_init error path

.. caused by a missing semi-colon, introduced in commit 0fc13c89
("cciss: fix cciss_revalidate panic").
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Reported-by: Thiago Farina <tfransosi@gmail.com>
Cc: Jens Axboe <jaxboe@fusionio.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

* 'v4l_for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mchehab/linux-2.6:
  [media] gspca - sonixj: Better handling of the bridge registers 0x01 and 0x17
  [media] gspca - sonixj: Add the bit definitions of the bridge reg 0x01 and 0x17
  [media] gspca - sonixj: Set the flag for some devices
  [media] gspca - sonixj: Add a flag in the driver_info table
  [media] gspca - sonixj: Fix a bad probe exchange
  [media] gspca - sonixj: Move bridge init to sd start
  [media] bttv: remove unneeded locking comments
  [media] bttv: fix mutex use before init (BZ#24602)
  [media] Don't export format_by_forcc on two different drivers

Merge branch 'rmobile-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/lethal/sh-2.6

* 'rmobile-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/lethal/sh-2.6:
  ARM: mach-shmobile: INTC interrupt priority level demux fix
  ARM: mach-shmobile: fix compile warning in mm/init.c

* 'sh-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/lethal/sh-2.6:
  clocksource: sh_cmt: Remove nested spinlock fix

Merge branch 'fbdev-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/lethal/fbdev-2.6

* 'fbdev-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/lethal/fbdev-2.6:
  OMAP: OMAPFB: disable old omapfb for OMAP4 builds
  OMAP: DSS: VRAM: Align start & size of vram to 2M

Merge branch 's5p-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/kgene/linux-samsung

* 's5p-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/kgene/linux-samsung:
  ARM: S5PV210: update MAX8998 platform data to get rid of WARN()
  ARM S3C24XX: Fix compilation of PM code for S3C2416
  ARM: S3C24XX: Fix CONFIG_S3C_DEV_NAND Kconfig entry

* 'for-linus' of git://git.kernel.dk/linux-2.6-block:
  cciss: fix cciss_revalidate panic
  block: max hardware sectors limit wrapper
  block: Deprecate QUEUE_FLAG_CLUSTER and use queue_limits instead
  blk-throttle: Correct the placement of smp_rmb()
  blk-throttle: Trim/adjust slice_end once a bio has been dispatched
  block: check for proper length of iov entries earlier in blk_rq_map_user_iov()
  drbd: fix for spin_lock_irqsave in endio callback
  drbd: don't recvmsg with zero length

Buggered-in: 76dda93c ("Btrfs: add snapshot/subvolume destroy
ioctl")
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Acked-by: Chris Mason <chris.mason@oracle.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

The cnt32_to_63 algorithm relies on proper counter data evaluation
ordering to work properly. This was missing from the provided
documentation.

Let's augment the documentation with the missing usage constraint and
fix the only instance that got it wrong.
Signed-off-by: Nicolas Pitre <nico@fluxnic.net>
Acked-by: David Howells <dhowells@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Merge branch 'sched-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip

* 'sched-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
  sched: Remove debugging check

Linus reported that the new warning introduced by commit f26f9aff
"Sched: fix skip_clock_update optimization" triggers. The need_resched
flag can be set by other CPUs asynchronously so this debug check is
bogus - remove it.
Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Mike Galbraith <efault@gmx.de>
LKML-Reference: <AANLkTinJ8hAG1TpyC+CSYPR47p48+1=E7fiC45hMXT_1@mail.gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

Merge branches 'x86-fixes-for-linus' and 'perf-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip

* 'x86-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
  x86-32: Make sure we can map all of lowmem if we need to
  x86, vt-d: Handle previous faults after enabling fault handling
  x86: Enable the intr-remap fault handling after local APIC setup
  x86, vt-d: Fix the vt-d fault handling irq migration in the x2apic mode
  x86, vt-d: Quirk for masking vtd spec errors to platform error handling logic
  x86, xsave: Use alloc_bootmem_align() instead of alloc_bootmem()
  bootmem: Add alloc_bootmem_align()
  x86, gcc-4.6: Use gcc -m options when building vdso
  x86: HPET: Chose a paranoid safe value for the ETIME check
  x86: io_apic: Avoid unused variable warning when CONFIG_GENERIC_PENDING_IRQ=n

* 'perf-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
  perf: Fix off by one in perf_swevent_init()
  perf: Fix duplicate events with multiple-pmu vs software events
  ftrace: Have recordmcount honor endianness in fn_ELF_R_INFO
  scripts/tags.sh: Add magic for trace-events
  tracing: Fix panic when lseek() called on "trace" opened for writing

Merge branch 'sched-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip

* 'sched-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
  sched: Fix the irqtime code for 32bit
  sched: Fix the irqtime code to deal with u64 wraps
  nohz: Fix get_next_timer_interrupt() vs cpu hotplug
  Sched: fix skip_clock_update optimization
  sched: Cure more NO_HZ load average woes

* git://git.kernel.org/pub/scm/linux/kernel/git/cmetcalf/linux-tile:
  arch/tile: handle rt_sigreturn() more cleanly
  arch/tile: handle CLONE_SETTLS in copy_thread(), not user space

* 'upstream' of git://git.linux-mips.org/pub/scm/upstream-linus:
  MIPS: Fix build errors in sc-mips.c

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jbarnes/pci-2.6:
  x86: avoid high BIOS area when allocating address space
  x86: avoid E820 regions when allocating address space
  x86: avoid low BIOS area when allocating address space
  resources: add arch hook for preventing allocation in reserved areas
  Revert "resources: support allocating space within a region from the top down"
  Revert "PCI: allocate bus resources from the top down"
  Revert "x86/PCI: allocate space from the end of a region, not the beginning"
  Revert "x86: allocate space within a region top-down"
  Revert "PCI: fix pci_bus_alloc_resource() hang, prefer positive decode"
  PCI: Update MCP55 quirk to not affect non HyperTransport variants

The current tile rt_sigreturn() syscall pattern uses the common idiom
of loading up pt_regs with all the saved registers from the time of
the signal, then anticipating the fact that we will clobber the ABI
"return value" register (r0) as we return from the syscall by setting
the rt_sigreturn return value to whatever random value was in the pt_regs
for r0.

However, this breaks in our 64-bit kernel when running "compat" tasks,
since we always sign-extend the "return value" register to properly
handle returned pointers that are in the upper 2GB of the 32-bit compat
address space.  Doing this to the sigreturn path then causes occasional
random corruption of the 64-bit r0 register.

Instead, we stop doing the crazy "load the return-value register"
hack in sigreturn.  We already have some sigreturn-specific assembly
code that we use to pass the pt_regs pointer to C code.  We extend that
code to also set the link register to point to a spot a few instructions
after the usual syscall return address so we don't clobber the saved r0.
Now it no longer matters what the rt_sigreturn syscall returns, and the
pt_regs structure can be cleanly and completely reloaded.
Signed-off-by: Chris Metcalf <cmetcalf@tilera.com>

Previously we were just setting up the "tp" register in the
new task as started by clone() in libc.  However, this is not
quite right, since in principle a signal might be delivered to
the new task before it had its TLS set up.  (Of course, this race
window still exists for resetting the libc getpid() cached value
in the new task, in principle.  But in any case, we are now doing
this exactly the way all other architectures do it.)

This change is important for 2.6.37 since the tile glibc we will
be submitting upstream will not set TLS in user space any more,
so it will only work on a kernel that has this fix.  It should
also be taken for 2.6.36.x in the stable tree if possible.
Signed-off-by: Chris Metcalf <cmetcalf@tilera.com>
Cc: stable <stable@kernel.org>

The initial values of the registers 0x01 and 0x17 are taken from the sensor
table at capture start and updated according to the flag PDN_INV.

Their values are updated at each step of the capture initialization and
memorized for reuse in capture stop.

This patch also fixed automatically some bad hardcoded values of these
registers.
Signed-off-by: Jean-François Moine <moinejf@free.fr>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

Signed-off-by: Jean-François Moine <moinejf@free.fr>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

The flag PDN_INV indicates that the sensor pin S_PWR_DN has not the same
value as other webcams with the same sensor. For now, only two webcams have
been so detected: the Microsoft's VX1000 and VX3000.
Signed-off-by: Jean-François Moine <moinejf@free.fr>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

Signed-off-by: Jean-François Moine <moinejf@free.fr>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

Signed-off-by: Jean-François Moine <moinejf@free.fr>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

Signed-off-by: Jean-François Moine <moinejf@free.fr>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

After Mauro's "bttv: Fix locking issues due to BKL removal code" there
are a number of comments that are no longer needed about lock ordering.
Remove them.
Signed-off-by: Brandon Philips <bphilips@suse.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

Fix a regression where bttv driver causes oopses when loading, since it
were using some non-initialized mutexes. While it would be possible to
fix the issue, there are some other lock troubles, like to the presence of
lock code at free_btres_lock().

It is possible to fix, but the better is to just use the core-assisted
locking schema. This way, V4L2 core will serialize access to all
ioctl's/open/close/mmap/read/poll operations, avoiding to have two
processes accessing the hardware at the same time. Also, as there's just
one lock, instead of 3, there's no risk of dead locks.

The net result is a cleaner code, with just one lock.
Reported-by: Dan Carpenter <error27@gmail.com>
Reported-by: Brandon Philips<brandon@ifup.org>
Reported-by: Chris Clayton <chris2553@googlemail.com>
Reported-by: Torsten Kaiser <just.for.lkml@googlemail.com>
Tested-by: Chris Clayton <chris2553@googlemail.com>
Tested-by: Torsten Kaiser <just.for.lkml@googlemail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

This restores parentheses blance.
Signed-off-by: Mariusz Kozlowski <mk@lab.zgora.pl>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

When the current __call_rcu() function was written, the expedited
APIs did not exist.  The __call_rcu() implementation therefore went
to great lengths to detect the end of old grace periods and to start
new ones, all in the name of reducing grace-period latency.  Now the
expedited APIs do exist, and the usage of __call_rcu() has increased
considerably.  This commit therefore causes __call_rcu() to avoid
worrying about grace periods unless there are a large number of
RCU callbacks stacked up on the current CPU.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

Some recent benchmarks have indicated possible lock contention on the
leaf-level rcu_node locks.  This commit therefore limits the number of
CPUs per leaf-level rcu_node structure to 16, in other words, there
can be at most 16 rcu_data structures fanning into a given rcu_node
structure.  Prior to this, the limit was 32 on 32-bit systems and 64 on
64-bit systems.

Note that the fanout of non-leaf rcu_node structures is unchanged.  The
organization of accesses to the rcu_node tree is such that references
to non-leaf rcu_node structures are much less frequent than to the
leaf structures.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

Use the CPU's bit in rnp->qsmask to determine whether or not the CPU
should try to report a quiescent state.  Handle overflow in the check
for rdp->gpnum having fallen behind.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

When a CPU that was in an extended quiescent state wakes
up and catches up with grace periods that remote CPUs
completed on its behalf, we update the completed field
but not the gpnum that keeps a stale value of a backward
grace period ID.

Later, note_new_gpnum() will interpret the shift between
the local CPU and the node grace period ID as some new grace
period to handle and will then start to hunt quiescent state.

But if every grace periods have already been completed, this
interpretation becomes broken. And we'll be stuck in clusters
of spurious softirqs because rcu_report_qs_rdp() will make
this broken state run into infinite loop.

The solution, as suggested by Lai Jiangshan, is to ensure that
the gpnum and completed fields are well synchronized when we catch
up with completed grace periods on their behalf by other cpus.
This way we won't start noting spurious new grace periods.
Suggested-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Steven Rostedt <rostedt@goodmis.org
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

When a CPU is idle and others CPUs handled its extended
quiescent state to complete grace periods on its behalf,
it will catch up with completed grace periods numbers
when it wakes up.

But at this point there might be no more grace period to
complete, but still the woken CPU always keeps its stale
qs_pending value and will then continue to chase quiescent
states even if its not needed anymore.

This results in clusters of spurious softirqs until a new
real grace period is started. Because if we continue to
chase quiescent states but we have completed every grace
periods, rcu_report_qs_rdp() is puzzled and makes that
state run into infinite loops.

As suggested by Lai Jiangshan, just reset qs_pending if
someone completed every grace periods on our behalf.
Suggested-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

The fix in commit #6a0cc49 requires more than three concurrent instances
of synchronize_sched_expedited() before batching is possible.  This
patch uses a ticket-counter-like approach that is also not unrelated to
Lai Jiangshan's Ring RCU to allow sharing of expedited grace periods even
when there are only two concurrent instances of synchronize_sched_expedited().

This commit builds on Tejun's original posting, which may be found at
http://lkml.org/lkml/2010/11/9/204, adding memory barriers, avoiding
overflow of signed integers (other than via atomic_t), and fixing the
detection of batching.
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>