---

yaml
---
r: 235278
b: refs/heads/master
c: 2e270d8
h: refs/heads/master
v: v3

[refs]

@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 60ed8cf78f886753e454b671841c0a3a0e55e915
+refs/heads/master: 2e270d84223262a38d4755c61d55f5c73ea89e56

trunk/Documentation/00-INDEX

@@ -328,8 +328,6 @@ sysrq.txt
 	- info on the magic SysRq key.
 telephony/
 	- directory with info on telephony (e.g. voice over IP) support.
-time_interpolators.txt
-	- info on time interpolators.
 uml/
 	- directory with information about User Mode Linux.
 unicode.txt
@@ -346,8 +344,6 @@ vm/
 	- directory with info on the Linux vm code.
 volatile-considered-harmful.txt
 	- Why the "volatile" type class should not be used
-voyager.txt
-	- guide to running Linux on the Voyager architecture.
 w1/
 	- directory with documents regarding the 1-wire (w1) subsystem.
 watchdog/

trunk/Documentation/ABI/testing/sysfs-devices-power

@@ -29,9 +29,8 @@ Description:
 		"disabled" to it.
 
 		For the devices that are not capable of generating system wakeup
-		events this file contains "\n".  In that cases the user space
-		cannot modify the contents of this file and the device cannot be
-		enabled to wake up the system.
+		events this file is not present.  In that case the device cannot
+		be enabled to wake up the system from sleep states.
 
 What:		/sys/devices/.../power/control
 Date:		January 2009
@@ -85,7 +84,7 @@ Description:
 		The /sys/devices/.../wakeup_count attribute contains the number
 		of signaled wakeup events associated with the device.  This
 		attribute is read-only.  If the device is not enabled to wake up
-		the system from sleep states, this attribute is empty.
+		the system from sleep states, this attribute is not present.
 
 What:		/sys/devices/.../power/wakeup_active_count
 Date:		September 2010
@@ -95,7 +94,7 @@ Description:
 		number of times the processing of wakeup events associated with
 		the device was completed (at the kernel level).  This attribute
 		is read-only.  If the device is not enabled to wake up the
-		system from sleep states, this attribute is empty.
+		system from sleep states, this attribute is not present.
 
 What:		/sys/devices/.../power/wakeup_hit_count
 Date:		September 2010
@@ -105,7 +104,8 @@ Description:
 		number of times the processing of a wakeup event associated with
 		the device might prevent the system from entering a sleep state.
 		This attribute is read-only.  If the device is not enabled to
-		wake up the system from sleep states, this attribute is empty.
+		wake up the system from sleep states, this attribute is not
+		present.
 
 What:		/sys/devices/.../power/wakeup_active
 Date:		September 2010
@@ -115,7 +115,7 @@ Description:
 		or 0, depending on whether or not a wakeup event associated with
 		the device is being processed (1).  This attribute is read-only.
 		If the device is not enabled to wake up the system from sleep
-		states, this attribute is empty.
+		states, this attribute is not present.
 
 What:		/sys/devices/.../power/wakeup_total_time_ms
 Date:		September 2010
@@ -125,7 +125,7 @@ Description:
 		the total time of processing wakeup events associated with the
 		device, in milliseconds.  This attribute is read-only.  If the
 		device is not enabled to wake up the system from sleep states,
-		this attribute is empty.
+		this attribute is not present.
 
 What:		/sys/devices/.../power/wakeup_max_time_ms
 Date:		September 2010
@@ -135,7 +135,7 @@ Description:
 		the maximum time of processing a single wakeup event associated
 		with the device, in milliseconds.  This attribute is read-only.
 		If the device is not enabled to wake up the system from sleep
-		states, this attribute is empty.
+		states, this attribute is not present.
 
 What:		/sys/devices/.../power/wakeup_last_time_ms
 Date:		September 2010
@@ -146,7 +146,7 @@ Description:
 		signaling the last wakeup event associated with the device, in
 		milliseconds.  This attribute is read-only.  If the device is
 		not enabled to wake up the system from sleep states, this
-		attribute is empty.
+		attribute is not present.
 
 What:		/sys/devices/.../power/autosuspend_delay_ms
 Date:		September 2010

trunk/Documentation/CodingStyle

@@ -659,7 +659,7 @@ There are a number of driver model diagnostic macros in <linux/device.h>
 which you should use to make sure messages are matched to the right device
 and driver, and are tagged with the right level:  dev_err(), dev_warn(),
 dev_info(), and so forth.  For messages that aren't associated with a
-particular device, <linux/kernel.h> defines pr_debug() and pr_info().
+particular device, <linux/printk.h> defines pr_debug() and pr_info().
 
 Coming up with good debugging messages can be quite a challenge; and once
 you have them, they can be a huge help for remote troubleshooting.  Such
@@ -819,6 +819,3 @@ language C, URL: http://www.open-std.org/JTC1/SC22/WG14/
 Kernel CodingStyle, by greg@kroah.com at OLS 2002:
 http://www.kroah.com/linux/talks/ols_2002_kernel_codingstyle_talk/html/
 
---
-Last updated on 2007-July-13.
-

trunk/Documentation/RCU/whatisRCU.txt

@@ -849,6 +849,37 @@ All:  lockdep-checked RCU-protected pointer access
 See the comment headers in the source code (or the docbook generated
 from them) for more information.
 
+However, given that there are no fewer than four families of RCU APIs
+in the Linux kernel, how do you choose which one to use?  The following
+list can be helpful:
+
+a.	Will readers need to block?  If so, you need SRCU.
+
+b.	What about the -rt patchset?  If readers would need to block
+	in an non-rt kernel, you need SRCU.  If readers would block
+	in a -rt kernel, but not in a non-rt kernel, SRCU is not
+	necessary.
+
+c.	Do you need to treat NMI handlers, hardirq handlers,
+	and code segments with preemption disabled (whether
+	via preempt_disable(), local_irq_save(), local_bh_disable(),
+	or some other mechanism) as if they were explicit RCU readers?
+	If so, you need RCU-sched.
+
+d.	Do you need RCU grace periods to complete even in the face
+	of softirq monopolization of one or more of the CPUs?  For
+	example, is your code subject to network-based denial-of-service
+	attacks?  If so, you need RCU-bh.
+
+e.	Is your workload too update-intensive for normal use of
+	RCU, but inappropriate for other synchronization mechanisms?
+	If so, consider SLAB_DESTROY_BY_RCU.  But please be careful!
+
+f.	Otherwise, use RCU.
+
+Of course, this all assumes that you have determined that RCU is in fact
+the right tool for your job.
+
 
 8.  ANSWERS TO QUICK QUIZZES
 

trunk/Documentation/cgroups/cgroups.txt

@@ -349,6 +349,10 @@ To mount a cgroup hierarchy with all available subsystems, type:
 The "xxx" is not interpreted by the cgroup code, but will appear in
 /proc/mounts so may be any useful identifying string that you like.
 
+Note: Some subsystems do not work without some user input first.  For instance,
+if cpusets are enabled the user will have to populate the cpus and mems files
+for each new cgroup created before that group can be used.
+
 To mount a cgroup hierarchy with just the cpuset and memory
 subsystems, type:
 # mount -t cgroup -o cpuset,memory hier1 /dev/cgroup
@@ -426,6 +430,14 @@ You can attach the current shell task by echoing 0:
 
 # echo 0 > tasks
 
+Note: Since every task is always a member of exactly one cgroup in each
+mounted hierarchy, to remove a task from its current cgroup you must
+move it into a new cgroup (possibly the root cgroup) by writing to the
+new cgroup's tasks file.
+
+Note: If the ns cgroup is active, moving a process to another cgroup can
+fail.
+
 2.3 Mounting hierarchies by name
 --------------------------------
 

trunk/Documentation/devicetree/00-INDEX

@@ -0,0 +1,10 @@
+Documentation for device trees, a data structure by which bootloaders pass
+hardware layout to Linux in a device-independent manner, simplifying hardware
+probing.  This subsystem is maintained by Grant Likely
+<grant.likely@secretlab.ca> and has a mailing list at
+https://lists.ozlabs.org/listinfo/devicetree-discuss
+
+00-INDEX
+	- this file
+booting-without-of.txt
+	- Booting Linux without Open Firmware, describes history and format of device trees.

trunk/Documentation/keys-request-key.txt

@@ -127,14 +127,15 @@ This is because process A's keyrings can't simply be attached to
 of them, and (b) it requires the same UID/GID/Groups all the way through.
 
 
-======================
-NEGATIVE INSTANTIATION
-======================
+====================================
+NEGATIVE INSTANTIATION AND REJECTION
+====================================
 
 Rather than instantiating a key, it is possible for the possessor of an
 authorisation key to negatively instantiate a key that's under construction.
 This is a short duration placeholder that causes any attempt at re-requesting
-the key whilst it exists to fail with error ENOKEY.
+the key whilst it exists to fail with error ENOKEY if negated or the specified
+error if rejected.
 
 This is provided to prevent excessive repeated spawning of /sbin/request-key
 processes for a key that will never be obtainable.

trunk/Documentation/keys.txt

@@ -637,6 +637,9 @@ The keyctl syscall functions are:
 	long keyctl(KEYCTL_INSTANTIATE, key_serial_t key,
 		    const void *payload, size_t plen,
 		    key_serial_t keyring);
+	long keyctl(KEYCTL_INSTANTIATE_IOV, key_serial_t key,
+		    const struct iovec *payload_iov, unsigned ioc,
+		    key_serial_t keyring);
 
      If the kernel calls back to userspace to complete the instantiation of a
      key, userspace should use this call to supply data for the key before the
@@ -652,11 +655,16 @@ The keyctl syscall functions are:
 
      The payload and plen arguments describe the payload data as for add_key().
 
+     The payload_iov and ioc arguments describe the payload data in an iovec
+     array instead of a single buffer.
+
 
  (*) Negatively instantiate a partially constructed key.
 
 	long keyctl(KEYCTL_NEGATE, key_serial_t key,
 		    unsigned timeout, key_serial_t keyring);
+	long keyctl(KEYCTL_REJECT, key_serial_t key,
+		    unsigned timeout, unsigned error, key_serial_t keyring);
 
      If the kernel calls back to userspace to complete the instantiation of a
      key, userspace should use this call mark the key as negative before the
@@ -669,6 +677,10 @@ The keyctl syscall functions are:
      that keyring, however all the constraints applying in KEYCTL_LINK apply in
      this case too.
 
+     If the key is rejected, future searches for it will return the specified
+     error code until the rejected key expires.  Negating the key is the same
+     as rejecting the key with ENOKEY as the error code.
+
 
  (*) Set the default request-key destination keyring.
 
@@ -1062,6 +1074,13 @@ The structure has a number of fields, some of which are mandatory:
      viable.
 
 
+ (*) int (*vet_description)(const char *description);
+
+     This optional method is called to vet a key description.  If the key type
+     doesn't approve of the key description, it may return an error, otherwise
+     it should return 0.
+
+
  (*) int (*instantiate)(struct key *key, const void *data, size_t datalen);
 
      This method is called to attach a payload to a key during construction.
@@ -1231,10 +1250,11 @@ hand the request off to (perhaps a path held in placed in another key by, for
 example, the KDE desktop manager).
 
 The program (or whatever it calls) should finish construction of the key by
-calling KEYCTL_INSTANTIATE, which also permits it to cache the key in one of
-the keyrings (probably the session ring) before returning. Alternatively, the
-key can be marked as negative with KEYCTL_NEGATE; this also permits the key to
-be cached in one of the keyrings.
+calling KEYCTL_INSTANTIATE or KEYCTL_INSTANTIATE_IOV, which also permits it to
+cache the key in one of the keyrings (probably the session ring) before
+returning.  Alternatively, the key can be marked as negative with KEYCTL_NEGATE
+or KEYCTL_REJECT; this also permits the key to be cached in one of the
+keyrings.
 
 If it returns with the key remaining in the unconstructed state, the key will
 be marked as being negative, it will be added to the session keyring, and an

trunk/Documentation/memory-barriers.txt

@@ -21,6 +21,7 @@ Contents:
      - SMP barrier pairing.
      - Examples of memory barrier sequences.
      - Read memory barriers vs load speculation.
+     - Transitivity
 
  (*) Explicit kernel barriers.
 
@@ -959,6 +960,63 @@ the speculation will be cancelled and the value reloaded:
 	retrieved                               :       :       +-------+
 
 
+TRANSITIVITY
+------------
+
+Transitivity is a deeply intuitive notion about ordering that is not
+always provided by real computer systems.  The following example
+demonstrates transitivity (also called "cumulativity"):
+
+	CPU 1			CPU 2			CPU 3
+	=======================	=======================	=======================
+		{ X = 0, Y = 0 }
+	STORE X=1		LOAD X			STORE Y=1
+				<general barrier>	<general barrier>
+				LOAD Y			LOAD X
+
+Suppose that CPU 2's load from X returns 1 and its load from Y returns 0.
+This indicates that CPU 2's load from X in some sense follows CPU 1's
+store to X and that CPU 2's load from Y in some sense preceded CPU 3's
+store to Y.  The question is then "Can CPU 3's load from X return 0?"
+
+Because CPU 2's load from X in some sense came after CPU 1's store, it
+is natural to expect that CPU 3's load from X must therefore return 1.
+This expectation is an example of transitivity: if a load executing on
+CPU A follows a load from the same variable executing on CPU B, then
+CPU A's load must either return the same value that CPU B's load did,
+or must return some later value.
+
+In the Linux kernel, use of general memory barriers guarantees
+transitivity.  Therefore, in the above example, if CPU 2's load from X
+returns 1 and its load from Y returns 0, then CPU 3's load from X must
+also return 1.
+
+However, transitivity is -not- guaranteed for read or write barriers.
+For example, suppose that CPU 2's general barrier in the above example
+is changed to a read barrier as shown below:
+
+	CPU 1			CPU 2			CPU 3
+	=======================	=======================	=======================
+		{ X = 0, Y = 0 }
+	STORE X=1		LOAD X			STORE Y=1
+				<read barrier>		<general barrier>
+				LOAD Y			LOAD X
+
+This substitution destroys transitivity: in this example, it is perfectly
+legal for CPU 2's load from X to return 1, its load from Y to return 0,
+and CPU 3's load from X to return 0.
+
+The key point is that although CPU 2's read barrier orders its pair
+of loads, it does not guarantee to order CPU 1's store.  Therefore, if
+this example runs on a system where CPUs 1 and 2 share a store buffer
+or a level of cache, CPU 2 might have early access to CPU 1's writes.
+General barriers are therefore required to ensure that all CPUs agree
+on the combined order of CPU 1's and CPU 2's accesses.
+
+To reiterate, if your code requires transitivity, use general barriers
+throughout.
+
+
 ========================
 EXPLICIT KERNEL BARRIERS
 ========================