---

yaml
---
r: 31693
b: refs/heads/master
c: a144a56
h: refs/heads/master
i:
  31691: 5fbd6b4
v: v3

[refs]

@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 3cbc96050b02d8e5764bd0970067ef294737e324
+refs/heads/master: a144a5633c1e625c3134c2ce8d549a054468fd98

trunk/Documentation/RCU/torture.txt

@@ -7,7 +7,7 @@ The CONFIG_RCU_TORTURE_TEST config option is available for all RCU
 implementations.  It creates an rcutorture kernel module that can
 be loaded to run a torture test.  The test periodically outputs
 status messages via printk(), which can be examined via the dmesg
-command (perhaps grepping for "rcutorture").  The test is started
+command (perhaps grepping for "torture").  The test is started
 when the module is loaded, and stops when the module is unloaded.
 
 However, actually setting this config option to "y" results in the system
@@ -35,21 +35,34 @@ stat_interval	The number of seconds between output of torture
 		be printed -only- when the module is unloaded, and this
 		is the default.
 
+shuffle_interval
+		The number of seconds to keep the test threads affinitied
+		to a particular subset of the CPUs.  Used in conjunction
+		with test_no_idle_hz.
+
+test_no_idle_hz	Whether or not to test the ability of RCU to operate in
+		a kernel that disables the scheduling-clock interrupt to
+		idle CPUs.  Boolean parameter, "1" to test, "0" otherwise.
+
+torture_type	The type of RCU to test: "rcu" for the rcu_read_lock()
+		API, "rcu_bh" for the rcu_read_lock_bh() API, and "srcu"
+		for the "srcu_read_lock()" API.
+
 verbose		Enable debug printk()s.  Default is disabled.
 
 
 OUTPUT
 
 The statistics output is as follows:
 
-	rcutorture: --- Start of test: nreaders=16 stat_interval=0 verbose=0
-	rcutorture: rtc: 0000000000000000 ver: 1916 tfle: 0 rta: 1916 rtaf: 0 rtf: 1915
-	rcutorture: Reader Pipe:  1466408 9747 0 0 0 0 0 0 0 0 0
-	rcutorture: Reader Batch:  1464477 11678 0 0 0 0 0 0 0 0
-	rcutorture: Free-Block Circulation:  1915 1915 1915 1915 1915 1915 1915 1915 1915 1915 0
-	rcutorture: --- End of test
+	rcu-torture: --- Start of test: nreaders=16 stat_interval=0 verbose=0
+	rcu-torture: rtc: 0000000000000000 ver: 1916 tfle: 0 rta: 1916 rtaf: 0 rtf: 1915
+	rcu-torture: Reader Pipe:  1466408 9747 0 0 0 0 0 0 0 0 0
+	rcu-torture: Reader Batch:  1464477 11678 0 0 0 0 0 0 0 0
+	rcu-torture: Free-Block Circulation:  1915 1915 1915 1915 1915 1915 1915 1915 1915 1915 0
+	rcu-torture: --- End of test
 
-The command "dmesg | grep rcutorture:" will extract this information on
+The command "dmesg | grep torture:" will extract this information on
 most systems.  On more esoteric configurations, it may be necessary to
 use other commands to access the output of the printk()s used by
 the RCU torture test.  The printk()s use KERN_ALERT, so they should
@@ -115,8 +128,9 @@ The following script may be used to torture RCU:
 	modprobe rcutorture
 	sleep 100
 	rmmod rcutorture
-	dmesg | grep rcutorture:
+	dmesg | grep torture:
 
 The output can be manually inspected for the error flag of "!!!".
 One could of course create a more elaborate script that automatically
-checked for such errors.
+checked for such errors.  The "rmmod" command forces a "SUCCESS" or
+"FAILURE" indication to be printk()ed.

trunk/Documentation/feature-removal-schedule.txt

@@ -177,6 +177,16 @@ Who:	Jean Delvare <khali@linux-fr.org>
 
 ---------------------------
 
+What:	Unused EXPORT_SYMBOL/EXPORT_SYMBOL_GPL exports
+	(temporary transition config option provided until then)
+	The transition config option will also be removed at the same time.
+When:	before 2.6.19
+Why:	Unused symbols are both increasing the size of the kernel binary
+	and are often a sign of "wrong API"
+Who:	Arjan van de Ven <arjan@linux.intel.com>
+
+---------------------------
+
 What:	remove EXPORT_SYMBOL(tasklist_lock)
 When:	August 2006
 Files:	kernel/fork.c

trunk/Documentation/kernel-parameters.txt

@@ -1669,6 +1669,10 @@ running once the system is up.
 	usbhid.mousepoll=
 			[USBHID] The interval which mice are to be polled at.
 
+	vdso=		[IA-32]
+			vdso=1: enable VDSO (default)
+			vdso=0: disable VDSO mapping
+
 	video=		[FB] Frame buffer configuration
 			See Documentation/fb/modedb.txt.
 

trunk/Documentation/pi-futex.txt

@@ -0,0 +1,121 @@
+Lightweight PI-futexes
+----------------------
+
+We are calling them lightweight for 3 reasons:
+
+ - in the user-space fastpath a PI-enabled futex involves no kernel work
+   (or any other PI complexity) at all. No registration, no extra kernel
+   calls - just pure fast atomic ops in userspace.
+
+ - even in the slowpath, the system call and scheduling pattern is very
+   similar to normal futexes.
+
+ - the in-kernel PI implementation is streamlined around the mutex
+   abstraction, with strict rules that keep the implementation
+   relatively simple: only a single owner may own a lock (i.e. no
+   read-write lock support), only the owner may unlock a lock, no
+   recursive locking, etc.
+
+Priority Inheritance - why?
+---------------------------
+
+The short reply: user-space PI helps achieving/improving determinism for
+user-space applications. In the best-case, it can help achieve
+determinism and well-bound latencies. Even in the worst-case, PI will
+improve the statistical distribution of locking related application
+delays.
+
+The longer reply:
+-----------------
+
+Firstly, sharing locks between multiple tasks is a common programming
+technique that often cannot be replaced with lockless algorithms. As we
+can see it in the kernel [which is a quite complex program in itself],
+lockless structures are rather the exception than the norm - the current
+ratio of lockless vs. locky code for shared data structures is somewhere
+between 1:10 and 1:100. Lockless is hard, and the complexity of lockless
+algorithms often endangers to ability to do robust reviews of said code.
+I.e. critical RT apps often choose lock structures to protect critical
+data structures, instead of lockless algorithms. Furthermore, there are
+cases (like shared hardware, or other resource limits) where lockless
+access is mathematically impossible.
+
+Media players (such as Jack) are an example of reasonable application
+design with multiple tasks (with multiple priority levels) sharing
+short-held locks: for example, a highprio audio playback thread is
+combined with medium-prio construct-audio-data threads and low-prio
+display-colory-stuff threads. Add video and decoding to the mix and
+we've got even more priority levels.
+
+So once we accept that synchronization objects (locks) are an
+unavoidable fact of life, and once we accept that multi-task userspace
+apps have a very fair expectation of being able to use locks, we've got
+to think about how to offer the option of a deterministic locking
+implementation to user-space.
+
+Most of the technical counter-arguments against doing priority
+inheritance only apply to kernel-space locks. But user-space locks are
+different, there we cannot disable interrupts or make the task
+non-preemptible in a critical section, so the 'use spinlocks' argument
+does not apply (user-space spinlocks have the same priority inversion
+problems as other user-space locking constructs). Fact is, pretty much
+the only technique that currently enables good determinism for userspace
+locks (such as futex-based pthread mutexes) is priority inheritance:
+
+Currently (without PI), if a high-prio and a low-prio task shares a lock
+[this is a quite common scenario for most non-trivial RT applications],
+even if all critical sections are coded carefully to be deterministic
+(i.e. all critical sections are short in duration and only execute a
+limited number of instructions), the kernel cannot guarantee any
+deterministic execution of the high-prio task: any medium-priority task
+could preempt the low-prio task while it holds the shared lock and
+executes the critical section, and could delay it indefinitely.
+
+Implementation:
+---------------
+
+As mentioned before, the userspace fastpath of PI-enabled pthread
+mutexes involves no kernel work at all - they behave quite similarly to
+normal futex-based locks: a 0 value means unlocked, and a value==TID
+means locked. (This is the same method as used by list-based robust
+futexes.) Userspace uses atomic ops to lock/unlock these mutexes without
+entering the kernel.
+
+To handle the slowpath, we have added two new futex ops:
+
+  FUTEX_LOCK_PI
+  FUTEX_UNLOCK_PI
+
+If the lock-acquire fastpath fails, [i.e. an atomic transition from 0 to
+TID fails], then FUTEX_LOCK_PI is called. The kernel does all the
+remaining work: if there is no futex-queue attached to the futex address
+yet then the code looks up the task that owns the futex [it has put its
+own TID into the futex value], and attaches a 'PI state' structure to
+the futex-queue. The pi_state includes an rt-mutex, which is a PI-aware,
+kernel-based synchronization object. The 'other' task is made the owner
+of the rt-mutex, and the FUTEX_WAITERS bit is atomically set in the
+futex value. Then this task tries to lock the rt-mutex, on which it
+blocks. Once it returns, it has the mutex acquired, and it sets the
+futex value to its own TID and returns. Userspace has no other work to
+perform - it now owns the lock, and futex value contains
+FUTEX_WAITERS|TID.
+
+If the unlock side fastpath succeeds, [i.e. userspace manages to do a
+TID -> 0 atomic transition of the futex value], then no kernel work is
+triggered.
+
+If the unlock fastpath fails (because the FUTEX_WAITERS bit is set),
+then FUTEX_UNLOCK_PI is called, and the kernel unlocks the futex on the
+behalf of userspace - and it also unlocks the attached
+pi_state->rt_mutex and thus wakes up any potential waiters.
+
+Note that under this approach, contrary to previous PI-futex approaches,
+there is no prior 'registration' of a PI-futex. [which is not quite
+possible anyway, due to existing ABI properties of pthread mutexes.]
+
+Also, under this scheme, 'robustness' and 'PI' are two orthogonal
+properties of futexes, and all four combinations are possible: futex,
+robust-futex, PI-futex, robust+PI-futex.
+
+More details about priority inheritance can be found in
+Documentation/rtmutex.txt.

trunk/Documentation/robust-futexes.txt

@@ -95,7 +95,7 @@ comparison. If the thread has registered a list, then normally the list
 is empty. If the thread/process crashed or terminated in some incorrect
 way then the list might be non-empty: in this case the kernel carefully
 walks the list [not trusting it], and marks all locks that are owned by
-this thread with the FUTEX_OWNER_DEAD bit, and wakes up one waiter (if
+this thread with the FUTEX_OWNER_DIED bit, and wakes up one waiter (if
 any).
 
 The list is guaranteed to be private and per-thread at do_exit() time,