Some blind people use a kernel engine called Speakup which uses hardware
synthesis to speak what gets displayed on the screen.  They use the
PC keyboard to control this engine (start/stop, accelerate, ...) and
also need to get keyboard feedback (to make sure to know what they are
typing, the caps lock status, etc.)

Up to now, the way it was done was very ugly.  Below is a patch to add a
notifier list for permitting a far better implementation, see ChangeLog
above for details.

You may wonder why this can't be done at the input layer.  The problem
is that what people want to monitor is the console keyboard, i.e. all
input keyboards that got attached to the console, and with the currently
active keymap (i.e. keysyms, not only keycodes).

This adds a keyboard notifier that such modules can use to get the keyboard
events and possibly eat them, at several stages:

- keycodes: even before translation into keysym.
- unbound keycodes: when no keysym is bound.
- unicode: when the keycode would get translated into a unicode character.
- keysym: when the keycode would get translated into a keysym.
- post_keysym: after the keysym got interpreted, so as to see the result
  (caps lock, etc.)

This also provides access to k_handler so as to permit simulation of
keypresses.

[akpm@linux-foundation.org: various fixes]
Signed-off-by: NSamuel Thibault <samuel.thibault@ens-lyon.org>
Cc: Jiri Kosina <jkosina@suse.cz>
Cc: Dmitry Torokhov <dtor@mail.ru>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

This patch adds code to allow errors to be passed up from event
handlers of NETDEV_REGISTER and NETDEV_CHANGENAME.  It also adds
the notifier_from_errno/notifier_to_errnor helpers to pass the
errno value up to the notifier caller.

If an error is detected when a device is registered, it causes
that operation to fail.  A NETDEV_UNREGISTER will be sent to
all event handlers.

Similarly if NETDEV_CHANGENAME fails the original name is restored
and a new NETDEV_CHANGENAME event is sent.

As such all event handlers must be idempotent with respect to
these events.

When an event handler is registered NETDEV_REGISTER events are
sent for all devices currently registered.  Should any of them
fail, we will send NETDEV_GOING_DOWN/NETDEV_DOWN/NETDEV_UNREGISTER
events to that handler for the devices which have already been
registered with it.  The handler registration itself will fail.
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Make it possible to register hibernation and suspend notifiers, so that
subsystems can perform hibernation-related or suspend-related operations that
should not be carried out by device drivers' .suspend() and .resume()
routines.

[akpm@linux-foundation.org: build fixes]
[akpm@linux-foundation.org: cleanups]
Signed-off-by: NRafael J. Wysocki <rjw@sisk.pl>
Acked-by: NPavel Machek <pavel@ucw.cz>
Cc: Nigel Cunningham <nigel@nigel.suspend2.net>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

KVM wants a notification when a cpu is about to die, so it can disable
hardware extensions, but at a time when user processes cannot be scheduled
on the cpu, so it doesn't try to use virtualization extensions after they
have been disabled.

This adds a CPU_DYING notification.  The notification is called in atomic
context on the doomed cpu.
Signed-off-by: NAvi Kivity <avi@qumranet.com>

Since nonboot CPUs are now disabled after tasks and devices have been
frozen and the CPU hotplug infrastructure is used for this purpose, we need
special CPU hotplug notifications that will help the CPU-hotplug-aware
subsystems distinguish normal CPU hotplug events from CPU hotplug events
related to a system-wide suspend or resume operation in progress.  This
patch introduces such notifications and causes them to be used during
suspend and resume transitions.  It also changes all of the
CPU-hotplug-aware subsystems to take these notifications into consideration
(for now they are handled in the same way as the corresponding "normal"
ones).

[oleg@tv-sign.ru: cleanups]
Signed-off-by: NRafael J. Wysocki <rjw@sisk.pl>
Cc: Gautham R Shenoy <ego@in.ibm.com>
Cc: Pavel Machek <pavel@ucw.cz>
Signed-off-by: NOleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

This is an attempt to provide an alternate mechanism for postponing
a hotplug event instead of using a global mechanism like lock_cpu_hotplug.

The proposal is to add two new events namely CPU_LOCK_ACQUIRE and
CPU_LOCK_RELEASE. The notification for these two events would be sent
out before and after a cpu_hotplug event respectively.

During the CPU_LOCK_ACQUIRE event, a cpu-hotplug-aware subsystem is
supposed to acquire any per-subsystem hotcpu mutex ( Eg. workqueue_mutex
in kernel/workqueue.c ).

During the CPU_LOCK_RELEASE release event the cpu-hotplug-aware subsystem
is supposed to release the per-subsystem hotcpu mutex.

The reasons for defining new events as opposed to reusing the existing events
like CPU_UP_PREPARE/CPU_UP_FAILED/CPU_ONLINE for locking/unlocking of
per-subsystem hotcpu mutexes are as follow:

	- CPU_LOCK_ACQUIRE: All hotcpu mutexes are taken before subsystems
	start handling pre-hotplug events like CPU_UP_PREPARE/CPU_DOWN_PREPARE
	etc, thus ensuring a clean handling of these events.

	- CPU_LOCK_RELEASE: The hotcpu mutexes will be released only after
	all subsystems have handled post-hotplug events like CPU_DOWN_FAILED,
	CPU_DEAD,CPU_ONLINE etc thereby ensuring that there are no subsequent
	clashes amongst the interdependent subsystems after a cpu hotplugs.

This patch also uses __raw_notifier_call chain in _cpu_up to take care
of the dependency between the two consequetive calls to
raw_notifier_call_chain.

[akpm@linux-foundation.org: fix a bug]
Signed-off-by: NGautham R Shenoy <ego@in.ibm.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Since 2.6.18-something, the community has been bugged by the problem to
provide a clean and a stable mechanism to postpone a cpu-hotplug event as
lock_cpu_hotplug was badly broken.

This is another proposal towards solving that problem.  This one is along the
lines of the solution provided in kernel/workqueue.c

Instead of having a global mechanism like lock_cpu_hotplug, we allow the
subsytems to define their own per-subsystem hot cpu mutexes.  These would be
taken(released) where ever we are currently calling
lock_cpu_hotplug(unlock_cpu_hotplug).

Also, in the per-subsystem hotcpu callback function,we take this mutex before
we handle any pre-cpu-hotplug events and release it once we finish handling
the post-cpu-hotplug events.  A standard means for doing this has been
provided in [PATCH 2/4] and demonstrated in [PATCH 3/4].

The ordering of these per-subsystem mutexes might still prove to be a
problem, but hopefully lockdep should help us get out of that muddle.

The patch set to be applied against linux-2.6.19-rc5 is as follows:

[PATCH 1/4] :	Extend notifier_call_chain with an option to specify the
		number of notifications to be sent and also count the
		number of notifications actually sent.

[PATCH 2/4] :	Define events CPU_LOCK_ACQUIRE and CPU_LOCK_RELEASE
		and send out notifications for these in _cpu_up and
		_cpu_down. This would help us standardise the acquire and
		release of the subsystem locks in the hotcpu
		callback functions of these subsystems.

[PATCH 3/4] :	Eliminate lock_cpu_hotplug from kernel/sched.c.

[PATCH 4/4] :	In workqueue_cpu_callback function, acquire(release) the
		workqueue_mutex while handling
		CPU_LOCK_ACQUIRE(CPU_LOCK_RELEASE).

If the per-subsystem-locking approach survives the test of time, we can expect
a slow phasing out of lock_cpu_hotplug, which has not yet been eliminated in
these patches :)

This patch:

Provide notifier_call_chain with an option to call only a specified number of
notifiers and also record the number of call to notifiers made.

The need for this enhancement was identified in the post entitled
"Slab - Eliminate lock_cpu_hotplug from slab"
(http://lkml.org/lkml/2006/10/28/92) by Ravikiran G Thirumalai and
Andrew Morton.

This patch adds two additional parameters to notifier_call_chain API namely
 - int nr_to_calls : Number of notifier_functions to be called.
 		     The don't care value is -1.

 - unsigned int *nr_calls : Records the total number of notifier_funtions
			    called by notifier_call_chain. The don't care
			    value is NULL.

[michal.k.k.piotrowski@gmail.com: build fix]
Credit: Andrew Morton <akpm@osdl.org>
Signed-off-by: NGautham R Shenoy <ego@in.ibm.com>
Signed-off-by: NMichal Piotrowski <michal.k.k.piotrowski@gmail.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

This patch (as751) adds a new type of notifier chain, based on the SRCU
(Sleepable Read-Copy Update) primitives recently added to the kernel.  An
SRCU notifier chain is much like a blocking notifier chain, in that it must
be called in process context and its callout routines are allowed to sleep.
 The difference is that the chain's links are protected by the SRCU
mechanism rather than by an rw-semaphore, so calling the chain has
extremely low overhead: no memory barriers and no cache-line bouncing.  On
the other hand, unregistering from the chain is expensive and the chain
head requires special runtime initialization (plus cleanup if it is to be
deallocated).

SRCU notifiers are appropriate for notifiers that will be called very
frequently and for which unregistration occurs very seldom.  The proposed
"task notifier" scheme qualifies, as may some of the network notifiers.
Signed-off-by: NAlan Stern <stern@rowland.harvard.edu>
Acked-by: NPaul E. McKenney <paulmck@us.ibm.com>
Acked-by: NChandra Seetharaman <sekharan@us.ibm.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Locking init improvement:

 - introduce and use __SPIN_LOCK_UNLOCKED for array initializations,
   to pass in the name string of locks, used by debugging
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NArjan van de Ven <arjan@linux.intel.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

The kernel's implementation of notifier chains is unsafe.  There is no
protection against entries being added to or removed from a chain while the
chain is in use.  The issues were discussed in this thread:

    http://marc.theaimsgroup.com/?l=linux-kernel&m=113018709002036&w=2

We noticed that notifier chains in the kernel fall into two basic usage
classes:

	"Blocking" chains are always called from a process context
	and the callout routines are allowed to sleep;

	"Atomic" chains can be called from an atomic context and
	the callout routines are not allowed to sleep.

We decided to codify this distinction and make it part of the API.  Therefore
this set of patches introduces three new, parallel APIs: one for blocking
notifiers, one for atomic notifiers, and one for "raw" notifiers (which is
really just the old API under a new name).  New kinds of data structures are
used for the heads of the chains, and new routines are defined for
registration, unregistration, and calling a chain.  The three APIs are
explained in include/linux/notifier.h and their implementation is in
kernel/sys.c.

With atomic and blocking chains, the implementation guarantees that the chain
links will not be corrupted and that chain callers will not get messed up by
entries being added or removed.  For raw chains the implementation provides no
guarantees at all; users of this API must provide their own protections.  (The
idea was that situations may come up where the assumptions of the atomic and
blocking APIs are not appropriate, so it should be possible for users to
handle these things in their own way.)

There are some limitations, which should not be too hard to live with.  For
atomic/blocking chains, registration and unregistration must always be done in
a process context since the chain is protected by a mutex/rwsem.  Also, a
callout routine for a non-raw chain must not try to register or unregister
entries on its own chain.  (This did happen in a couple of places and the code
had to be changed to avoid it.)

Since atomic chains may be called from within an NMI handler, they cannot use
spinlocks for synchronization.  Instead we use RCU.  The overhead falls almost
entirely in the unregister routine, which is okay since unregistration is much
less frequent that calling a chain.

Here is the list of chains that we adjusted and their classifications.  None
of them use the raw API, so for the moment it is only a placeholder.

  ATOMIC CHAINS
  -------------
arch/i386/kernel/traps.c:		i386die_chain
arch/ia64/kernel/traps.c:		ia64die_chain
arch/powerpc/kernel/traps.c:		powerpc_die_chain
arch/sparc64/kernel/traps.c:		sparc64die_chain
arch/x86_64/kernel/traps.c:		die_chain
drivers/char/ipmi/ipmi_si_intf.c:	xaction_notifier_list
kernel/panic.c:				panic_notifier_list
kernel/profile.c:			task_free_notifier
net/bluetooth/hci_core.c:		hci_notifier
net/ipv4/netfilter/ip_conntrack_core.c:	ip_conntrack_chain
net/ipv4/netfilter/ip_conntrack_core.c:	ip_conntrack_expect_chain
net/ipv6/addrconf.c:			inet6addr_chain
net/netfilter/nf_conntrack_core.c:	nf_conntrack_chain
net/netfilter/nf_conntrack_core.c:	nf_conntrack_expect_chain
net/netlink/af_netlink.c:		netlink_chain

  BLOCKING CHAINS
  ---------------
arch/powerpc/platforms/pseries/reconfig.c:	pSeries_reconfig_chain
arch/s390/kernel/process.c:		idle_chain
arch/x86_64/kernel/process.c		idle_notifier
drivers/base/memory.c:			memory_chain
drivers/cpufreq/cpufreq.c		cpufreq_policy_notifier_list
drivers/cpufreq/cpufreq.c		cpufreq_transition_notifier_list
drivers/macintosh/adb.c:		adb_client_list
drivers/macintosh/via-pmu.c		sleep_notifier_list
drivers/macintosh/via-pmu68k.c		sleep_notifier_list
drivers/macintosh/windfarm_core.c	wf_client_list
drivers/usb/core/notify.c		usb_notifier_list
drivers/video/fbmem.c			fb_notifier_list
kernel/cpu.c				cpu_chain
kernel/module.c				module_notify_list
kernel/profile.c			munmap_notifier
kernel/profile.c			task_exit_notifier
kernel/sys.c				reboot_notifier_list
net/core/dev.c				netdev_chain
net/decnet/dn_dev.c:			dnaddr_chain
net/ipv4/devinet.c:			inetaddr_chain

It's possible that some of these classifications are wrong.  If they are,
please let us know or submit a patch to fix them.  Note that any chain that
gets called very frequently should be atomic, because the rwsem read-locking
used for blocking chains is very likely to incur cache misses on SMP systems.
(However, if the chain's callout routines may sleep then the chain cannot be
atomic.)

The patch set was written by Alan Stern and Chandra Seetharaman, incorporating
material written by Keith Owens and suggestions from Paul McKenney and Andrew
Morton.

[jes@sgi.com: restructure the notifier chain initialization macros]
Signed-off-by: NAlan Stern <stern@rowland.harvard.edu>
Signed-off-by: NChandra Seetharaman <sekharan@us.ibm.com>
Signed-off-by: NJes Sorensen <jes@sgi.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Resend of earlier patch (no changes) from Catalin used to provide
device feature change notification.

Signed-off-by: Catalin BOIE <catab at umbrella.ro>
Acked-by: NStephen Hemminger <shemminger@osdl.org>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.

Let it rip!