---

yaml
---
r: 22398
b: refs/heads/master
c: 5812499
h: refs/heads/master
v: v3

[refs]

@@ -1,2 +1,2 @@
 ---
-refs/heads/master: b0a06623dc4caf6dfb6a84419507643471676d20
+refs/heads/master: 581249966ffeb0463bad1b0e087e1bb29ed53707

trunk/CREDITS

@@ -120,7 +120,6 @@ D: Author of lil (Linux Interrupt Latency benchmark)
 D: Fixed the shm swap deallocation at swapoff time (try_to_unuse message)
 D: VM hacker
 D: Various other kernel hacks
-S: Via Cicalini 26
 S: Imola 40026
 S: Italy
 
@@ -3101,7 +3100,7 @@ S: Minto, NSW, 2566
 S: Australia
 
 N: Stephen Smalley
-E: sds@epoch.ncsc.mil
+E: sds@tycho.nsa.gov
 D: portions of the Linux Security Module (LSM) framework and security modules
 
 N: Chris Smith
@@ -3643,11 +3642,9 @@ S: Cambridge. CB1 7EG
 S: England
 
 N: Chris Wright
-E: chrisw@osdl.org
+E: chrisw@sous-sol.org
 D: hacking on LSM framework and security modules.
-S: c/o OSDL
-S: 12725 SW Millikan Way, Suite 400
-S: Beaverton, OR 97005
+S: Portland, OR
 S: USA
 
 N: Michal Wronski

trunk/Documentation/RCU/RTFP.txt

@@ -90,16 +90,20 @@ at OLS.  The resulting abundance of RCU patches was presented the
 following year [McKenney02a], and use of RCU in dcache was first
 described that same year [Linder02a].
 
-Also in 2002, Michael [Michael02b,Michael02a] presented techniques
-that defer the destruction of data structures to simplify non-blocking
-synchronization (wait-free synchronization, lock-free synchronization,
-and obstruction-free synchronization are all examples of non-blocking
-synchronization).  In particular, this technique eliminates locking,
-reduces contention, reduces memory latency for readers, and parallelizes
-pipeline stalls and memory latency for writers.  However, these
-techniques still impose significant read-side overhead in the form of
-memory barriers.  Researchers at Sun worked along similar lines in the
-same timeframe [HerlihyLM02,HerlihyLMS03].
+Also in 2002, Michael [Michael02b,Michael02a] presented "hazard-pointer"
+techniques that defer the destruction of data structures to simplify
+non-blocking synchronization (wait-free synchronization, lock-free
+synchronization, and obstruction-free synchronization are all examples of
+non-blocking synchronization).  In particular, this technique eliminates
+locking, reduces contention, reduces memory latency for readers, and
+parallelizes pipeline stalls and memory latency for writers.  However,
+these techniques still impose significant read-side overhead in the
+form of memory barriers.  Researchers at Sun worked along similar lines
+in the same timeframe [HerlihyLM02,HerlihyLMS03].  These techniques
+can be thought of as inside-out reference counts, where the count is
+represented by the number of hazard pointers referencing a given data
+structure (rather than the more conventional counter field within the
+data structure itself).
 
 In 2003, the K42 group described how RCU could be used to create
 hot-pluggable implementations of operating-system functions.  Later that
@@ -113,7 +117,6 @@ number of operating-system kernels [PaulEdwardMcKenneyPhD], a paper
 describing how to make RCU safe for soft-realtime applications [Sarma04c],
 and a paper describing SELinux performance with RCU [JamesMorris04b].
 
-
 2005 has seen further adaptation of RCU to realtime use, permitting
 preemption of RCU realtime critical sections [PaulMcKenney05a,
 PaulMcKenney05b].

trunk/Documentation/RCU/checklist.txt

@@ -177,3 +177,9 @@ over a rather long period of time, but improvements are always welcome!
 
 	If you want to wait for some of these other things, you might
 	instead need to use synchronize_irq() or synchronize_sched().
+
+12.	Any lock acquired by an RCU callback must be acquired elsewhere
+	with irq disabled, e.g., via spin_lock_irqsave().  Failing to
+	disable irq on a given acquisition of that lock will result in
+	deadlock as soon as the RCU callback happens to interrupt that
+	acquisition's critical section.

trunk/Documentation/RCU/listRCU.txt

@@ -232,7 +232,7 @@ entry does not exist.  For this to be helpful, the search function must
 return holding the per-entry spinlock, as ipc_lock() does in fact do.
 
 Quick Quiz:  Why does the search function need to return holding the
-per-entry lock for this deleted-flag technique to be helpful?
+	per-entry lock for this deleted-flag technique to be helpful?
 
 If the system-call audit module were to ever need to reject stale data,
 one way to accomplish this would be to add a "deleted" flag and a "lock"
@@ -275,8 +275,8 @@ flag under the spinlock as follows:
 	{
 		struct audit_entry  *e;
 
-		/* Do not use the _rcu iterator here, since this is the only
-		 * deletion routine. */
+		/* Do not need to use the _rcu iterator here, since this
+		 * is the only deletion routine. */
 		list_for_each_entry(e, list, list) {
 			if (!audit_compare_rule(rule, &e->rule)) {
 				spin_lock(&e->lock);
@@ -304,9 +304,12 @@ function to reject newly deleted data.
 
 
 Answer to Quick Quiz
-
-If the search function drops the per-entry lock before returning, then
-the caller will be processing stale data in any case.  If it is really
-OK to be processing stale data, then you don't need a "deleted" flag.
-If processing stale data really is a problem, then you need to hold the
-per-entry lock across all of the code that uses the value looked up.
+	Why does the search function need to return holding the per-entry
+	lock for this deleted-flag technique to be helpful?
+
+	If the search function drops the per-entry lock before returning,
+	then the caller will be processing stale data in any case.  If it
+	is really OK to be processing stale data, then you don't need a
+	"deleted" flag.  If processing stale data really is a problem,
+	then you need to hold the per-entry lock across all of the code
+	that uses the value that was returned.

trunk/Documentation/RCU/rcu.txt

@@ -111,6 +111,11 @@ o	What are all these files in this directory?
 
 		You are reading it!
 
+	rcuref.txt
+
+		Describes how to combine use of reference counts
+		with RCU.
+
 	whatisRCU.txt
 
 		Overview of how the RCU implementation works.  Along

trunk/Documentation/RCU/rcuref.txt

@@ -1,7 +1,7 @@
-Refcounter design for elements of lists/arrays protected by RCU.
+Reference-count design for elements of lists/arrays protected by RCU.
 
-Refcounting on elements of  lists which are protected by traditional
-reader/writer spinlocks or semaphores are straight forward as in:
+Reference counting on elements of lists which are protected by traditional
+reader/writer spinlocks or semaphores are straightforward:
 
 1.				2.
 add()				search_and_reference()
@@ -28,12 +28,12 @@ release_referenced()			delete()
 					    ...
 					}
 
-If this list/array is made lock free using rcu as in changing the
-write_lock in add() and delete() to spin_lock and changing read_lock
+If this list/array is made lock free using RCU as in changing the
+write_lock() in add() and delete() to spin_lock and changing read_lock
 in search_and_reference to rcu_read_lock(), the atomic_get in
 search_and_reference could potentially hold reference to an element which
-has already been deleted from the list/array.  atomic_inc_not_zero takes
-care of this scenario. search_and_reference should look as;
+has already been deleted from the list/array.  Use atomic_inc_not_zero()
+in this scenario as follows:
 
 1.					2.
 add()					search_and_reference()
@@ -51,17 +51,16 @@ add()					search_and_reference()
 release_referenced()			delete()
 {					{
     ...					    write_lock(&list_lock);
-    atomic_dec(&el->rc, relfunc)	    ...
-    ...					    delete_element
-}					    write_unlock(&list_lock);
- 					    ...
+    if (atomic_dec_and_test(&el->rc))       ...
+        call_rcu(&el->head, el_free);       delete_element
+    ...                                     write_unlock(&list_lock);
+} 					    ...
 					    if (atomic_dec_and_test(&el->rc))
 					        call_rcu(&el->head, el_free);
 					    ...
 					}
 
-Sometimes, reference to the element need to be obtained in the
-update (write) stream.  In such cases, atomic_inc_not_zero might be an
-overkill since the spinlock serialising list updates are held. atomic_inc
-is to be used in such cases.
-
+Sometimes, a reference to the element needs to be obtained in the
+update (write) stream.  In such cases, atomic_inc_not_zero() might be
+overkill, since we hold the update-side spinlock.  One might instead
+use atomic_inc() in such cases.

trunk/Documentation/RCU/whatisRCU.txt

@@ -200,10 +200,11 @@ rcu_assign_pointer()
 	the new value, and also executes any memory-barrier instructions
 	required for a given CPU architecture.
 
-	Perhaps more important, it serves to document which pointers
-	are protected by RCU.  That said, rcu_assign_pointer() is most
-	frequently used indirectly, via the _rcu list-manipulation
-	primitives such as list_add_rcu().
+	Perhaps just as important, it serves to document (1) which
+	pointers are protected by RCU and (2) the point at which a
+	given structure becomes accessible to other CPUs.  That said,
+	rcu_assign_pointer() is most frequently used indirectly, via
+	the _rcu list-manipulation primitives such as list_add_rcu().
 
 rcu_dereference()
 
@@ -258,9 +259,11 @@ rcu_dereference()
 	locking.
 
 	As with rcu_assign_pointer(), an important function of
-	rcu_dereference() is to document which pointers are protected
-	by RCU.  And, again like rcu_assign_pointer(), rcu_dereference()
-	is typically used indirectly, via the _rcu list-manipulation
+	rcu_dereference() is to document which pointers are protected by
+	RCU, in particular, flagging a pointer that is subject to changing
+	at any time, including immediately after the rcu_dereference().
+	And, again like rcu_assign_pointer(), rcu_dereference() is
+	typically used indirectly, via the _rcu list-manipulation
 	primitives, such as list_for_each_entry_rcu().
 
 The following diagram shows how each API communicates among the
@@ -327,7 +330,7 @@ for specialized uses, but are relatively uncommon.
 3.  WHAT ARE SOME EXAMPLE USES OF CORE RCU API?
 
 This section shows a simple use of the core RCU API to protect a
-global pointer to a dynamically allocated structure.  More typical
+global pointer to a dynamically allocated structure.  More-typical
 uses of RCU may be found in listRCU.txt, arrayRCU.txt, and NMI-RCU.txt.
 
 	struct foo {
@@ -410,6 +413,8 @@ o	Use synchronize_rcu() -after- removing a data element from an
 	data item.
 
 See checklist.txt for additional rules to follow when using RCU.
+And again, more-typical uses of RCU may be found in listRCU.txt,
+arrayRCU.txt, and NMI-RCU.txt.
 
 
 4.  WHAT IF MY UPDATING THREAD CANNOT BLOCK?
@@ -513,7 +518,7 @@ production-quality implementation, and see:
 
 for papers describing the Linux kernel RCU implementation.  The OLS'01
 and OLS'02 papers are a good introduction, and the dissertation provides
-more details on the current implementation.
+more details on the current implementation as of early 2004.
 
 
 5A.  "TOY" IMPLEMENTATION #1: LOCKING
@@ -768,7 +773,6 @@ RCU pointer/list traversal:
 	rcu_dereference
 	list_for_each_rcu		(to be deprecated in favor of
 					 list_for_each_entry_rcu)
-	list_for_each_safe_rcu		(deprecated, not used)
 	list_for_each_entry_rcu
 	list_for_each_continue_rcu	(to be deprecated in favor of new
 					 list_for_each_entry_continue_rcu)
@@ -807,7 +811,8 @@ Quick Quiz #1:	Why is this argument naive?  How could a deadlock
 Answer:		Consider the following sequence of events:
 
 		1.	CPU 0 acquires some unrelated lock, call it
-			"problematic_lock".
+			"problematic_lock", disabling irq via
+			spin_lock_irqsave().
 
 		2.	CPU 1 enters synchronize_rcu(), write-acquiring
 			rcu_gp_mutex.
@@ -894,7 +899,7 @@ Answer:		Just as PREEMPT_RT permits preemption of spinlock
 ACKNOWLEDGEMENTS
 
 My thanks to the people who helped make this human-readable, including
-Jon Walpole, Josh Triplett, Serge Hallyn, and Suzanne Wood.
+Jon Walpole, Josh Triplett, Serge Hallyn, Suzanne Wood, and Alan Stern.
 
 
 For more information, see http://www.rdrop.com/users/paulmck/RCU.

trunk/Documentation/cpu-hotplug.txt

@@ -11,6 +11,8 @@
 			Joel Schopp <jschopp@austin.ibm.com>
 		ia64/x86_64:
 			Ashok Raj <ashok.raj@intel.com>
+		s390:
+			Heiko Carstens <heiko.carstens@de.ibm.com>
 
 Authors: Ashok Raj <ashok.raj@intel.com>
 Lots of feedback: Nathan Lynch <nathanl@austin.ibm.com>,
@@ -44,9 +46,28 @@ maxcpus=n    Restrict boot time cpus to n. Say if you have 4 cpus, using
              maxcpus=2 will only boot 2. You can choose to bring the
              other cpus later online, read FAQ's for more info.
 
-additional_cpus=n	[x86_64 only] use this to limit hotpluggable cpus.
-                        This option sets
-			cpu_possible_map = cpu_present_map + additional_cpus
+additional_cpus*=n	Use this to limit hotpluggable cpus. This option sets
+  			cpu_possible_map = cpu_present_map + additional_cpus
+
+(*) Option valid only for following architectures
+- x86_64, ia64, s390
+
+ia64 and x86_64 use the number of disabled local apics in ACPI tables MADT
+to determine the number of potentially hot-pluggable cpus. The implementation
+should only rely on this to count the #of cpus, but *MUST* not rely on the
+apicid values in those tables for disabled apics. In the event BIOS doesnt
+mark such hot-pluggable cpus as disabled entries, one could use this
+parameter "additional_cpus=x" to represent those cpus in the cpu_possible_map.
+
+s390 uses the number of cpus it detects at IPL time to also the number of bits
+in cpu_possible_map. If it is desired to add additional cpus at a later time
+the number should be specified using this option or the possible_cpus option.
+
+possible_cpus=n		[s390 only] use this to set hotpluggable cpus.
+			This option sets possible_cpus bits in
+			cpu_possible_map. Thus keeping the numbers of bits set
+			constant even if the machine gets rebooted.
+			This option overrides additional_cpus.
 
 CPU maps and such
 -----------------

trunk/Documentation/cpusets.txt

@@ -4,8 +4,9 @@
 Copyright (C) 2004 BULL SA.
 Written by Simon.Derr@bull.net
 
-Portions Copyright (c) 2004 Silicon Graphics, Inc.
+Portions Copyright (c) 2004-2006 Silicon Graphics, Inc.
 Modified by Paul Jackson <pj@sgi.com>
+Modified by Christoph Lameter <clameter@sgi.com>
 
 CONTENTS:
 =========
@@ -90,7 +91,8 @@ This can be especially valuable on:
 
 These subsets, or "soft partitions" must be able to be dynamically
 adjusted, as the job mix changes, without impacting other concurrently
-executing jobs.
+executing jobs. The location of the running jobs pages may also be moved
+when the memory locations are changed.
 
 The kernel cpuset patch provides the minimum essential kernel
 mechanisms required to efficiently implement such subsets.  It
@@ -102,8 +104,8 @@ memory allocator code.
 1.3 How are cpusets implemented ?
 ---------------------------------
 
-Cpusets provide a Linux kernel (2.6.7 and above) mechanism to constrain
-which CPUs and Memory Nodes are used by a process or set of processes.
+Cpusets provide a Linux kernel mechanism to constrain which CPUs and
+Memory Nodes are used by a process or set of processes.
 
 The Linux kernel already has a pair of mechanisms to specify on which
 CPUs a task may be scheduled (sched_setaffinity) and on which Memory
@@ -371,22 +373,17 @@ cpusets memory placement policy 'mems' subsequently changes.
 If the cpuset flag file 'memory_migrate' is set true, then when
 tasks are attached to that cpuset, any pages that task had
 allocated to it on nodes in its previous cpuset are migrated
-to the tasks new cpuset.  Depending on the implementation,
-this migration may either be done by swapping the page out,
-so that the next time the page is referenced, it will be paged
-into the tasks new cpuset, usually on the node where it was
-referenced, or this migration may be done by directly copying
-the pages from the tasks previous cpuset to the new cpuset,
-where possible to the same node, relative to the new cpuset,
-as the node that held the page, relative to the old cpuset.
+to the tasks new cpuset. The relative placement of the page within
+the cpuset is preserved during these migration operations if possible.
+For example if the page was on the second valid node of the prior cpuset
+then the page will be placed on the second valid node of the new cpuset.
+
 Also if 'memory_migrate' is set true, then if that cpusets
 'mems' file is modified, pages allocated to tasks in that
 cpuset, that were on nodes in the previous setting of 'mems',
-will be moved to nodes in the new setting of 'mems.'  Again,
-depending on the implementation, this might be done by swapping,
-or by direct copying.  In either case, pages that were not in
-the tasks prior cpuset, or in the cpusets prior 'mems' setting,
-will not be moved.
+will be moved to nodes in the new setting of 'mems.'
+Pages that were not in the tasks prior cpuset, or in the cpusets
+prior 'mems' setting, will not be moved.
 
 There is an exception to the above.  If hotplug functionality is used
 to remove all the CPUs that are currently assigned to a cpuset,
@@ -434,16 +431,6 @@ and then start a subshell 'sh' in that cpuset:
   # The next line should display '/Charlie'
   cat /proc/self/cpuset
 
-In the case that a change of cpuset includes wanting to move already
-allocated memory pages, consider further the work of IWAMOTO
-Toshihiro <iwamoto@valinux.co.jp> for page remapping and memory
-hotremoval, which can be found at:
-
-  http://people.valinux.co.jp/~iwamoto/mh.html
-
-The integration of cpusets with such memory migration is not yet
-available.
-
 In the future, a C library interface to cpusets will likely be
 available.  For now, the only way to query or modify cpusets is
 via the cpuset file system, using the various cd, mkdir, echo, cat,