---

yaml
---
r: 19535
b: refs/heads/master
c: 59ed2f5
h: refs/heads/master
i:
  19533: ac003e6
  19531: ad610b3
  19527: a78b7ac
  19519: 0a174a6
v: v3

[refs]

@@ -1,2 +1,2 @@
 ---
-refs/heads/master: b8e4d89357fc434618a59c1047cac72641191805
+refs/heads/master: 59ed2f59e4ea6a32f9591e378da7935f713a7000

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/feature-removal-schedule.txt

@@ -148,3 +148,17 @@ Why:	The 8250 serial driver now has the ability to deal with the differences
 	brother on Alchemy SOCs.  The loss of features is not considered an
 	issue.
 Who:	Ralf Baechle <ralf@linux-mips.org>
+
+---------------------------
+
+What:	Legacy /proc/pci interface (PCI_LEGACY_PROC)
+When:	March 2006
+Why:	deprecated since 2.5.53 in favor of lspci(8)
+Who:	Adrian Bunk <bunk@stusta.de>
+
+---------------------------
+
+What:	pci_module_init(driver)
+When:	January 2007
+Why:	Is replaced by pci_register_driver(pci_driver).
+Who:	Richard Knutsson <ricknu-0@student.ltu.se> and Greg Kroah-Hartman <gregkh@suse.de>

trunk/Documentation/kernel-doc-nano-HOWTO.txt

@@ -45,10 +45,10 @@ How to extract the documentation
 
 If you just want to read the ready-made books on the various
 subsystems (see Documentation/DocBook/*.tmpl), just type 'make
-psdocs', or 'make pdfdocs', or 'make htmldocs', depending on your 
-preference.  If you would rather read a different format, you can type 
-'make sgmldocs' and then use DocBook tools to convert 
-Documentation/DocBook/*.sgml to a format of your choice (for example, 
+psdocs', or 'make pdfdocs', or 'make htmldocs', depending on your
+preference.  If you would rather read a different format, you can type
+'make sgmldocs' and then use DocBook tools to convert
+Documentation/DocBook/*.sgml to a format of your choice (for example,
 'db2html ...' if 'make htmldocs' was not defined).
 
 If you want to see man pages instead, you can do this:
@@ -124,6 +124,36 @@ patterns, which are highlighted appropriately.
 Take a look around the source tree for examples.
 
 
+kernel-doc for structs, unions, enums, and typedefs
+---------------------------------------------------
+
+Beside functions you can also write documentation for structs, unions,
+enums and typedefs. Instead of the function name you must write the name
+of the declaration;  the struct/union/enum/typedef must always precede
+the name. Nesting of declarations is not supported.
+Use the argument mechanism to document members or constants.
+
+Inside a struct description, you can use the "private:" and "public:"
+comment tags.  Structure fields that are inside a "private:" area
+are not listed in the generated output documentation.
+
+Example:
+
+/**
+ * struct my_struct - short description
+ * @a: first member
+ * @b: second member
+ *
+ * Longer description
+ */
+struct my_struct {
+    int a;
+    int b;
+/* private: */
+    int c;
+};
+
+
 How to make new SGML template files
 -----------------------------------
 
@@ -147,4 +177,3 @@ documentation, in <filename>, for the functions listed.
 
 Tim.
 */ <twaugh@redhat.com>
-

trunk/Documentation/power/interface.txt

@@ -44,7 +44,7 @@ it.
 /sys/power/image_size controls the size of the image created by
 the suspend-to-disk mechanism.  It can be written a string
 representing a non-negative integer that will be used as an upper
-limit of the image size, in megabytes.  The suspend-to-disk mechanism will
+limit of the image size, in bytes.  The suspend-to-disk mechanism will
 do its best to ensure the image size will not exceed that number.  However,
 if this turns out to be impossible, it will try to suspend anyway using the
 smallest image possible.  In particular, if "0" is written to this file, the

trunk/Documentation/power/swsusp.txt

@@ -27,7 +27,7 @@ echo shutdown > /sys/power/disk; echo disk > /sys/power/state
 
 echo platform > /sys/power/disk; echo disk > /sys/power/state
 
-If you want to limit the suspend image size to N megabytes, do
+If you want to limit the suspend image size to N bytes, do
 
 echo N > /sys/power/image_size