linux-toradex.git/include/linux/rcupdate.h, branch v3.8.12

context_tracking: New context tracking susbsystem

2012-11-30T19:40:07+00:00

Create a new subsystem that probes on kernel boundaries
to keep track of the transitions between level contexts
with two basic initial contexts: user or kernel.

This is an abstraction of some RCU code that use such tracking
to implement its userspace extended quiescent state.

We need to pull this up from RCU into this new level of indirection
because this tracking is also going to be used to implement an "on
demand" generic virtual cputime accounting. A necessary step to
shutdown the tick while still accounting the cputime.

Signed-off-by: Frederic Weisbecker 
Cc: Andrew Morton 
Cc: H. Peter Anvin 
Cc: Ingo Molnar 
Cc: Paul E. McKenney 
Cc: Peter Zijlstra 
Cc: Steven Rostedt 
Cc: Thomas Gleixner 
Cc: Li Zhong 
Cc: Gilad Ben-Yossef 
Reviewed-by: Steven Rostedt 
[ paulmck: fix whitespace error and email address. ]
Signed-off-by: Paul E. McKenney

Merge branches 'urgent.2012.10.27a', 'doc.2012.11.16a', 'fixes.2012.11.13a', 'srcu.2012.10.27a', 'stall.2012.11.13a', 'tracing.2012.11.08a' and 'idle.2012.10.24a' into HEAD

2012-11-16T17:59:58+00:00

urgent.2012.10.27a: Fix for RCU user-mode transition (already in -tip).

doc.2012.11.08a: Documentation updates, most notably codifying the
	memory-barrier guarantees inherent to grace periods.

fixes.2012.11.13a: Miscellaneous fixes.

srcu.2012.10.27a: Allow statically allocated and initialized srcu_struct
	structures (courtesy of Lai Jiangshan).

stall.2012.11.13a: Add more diagnostic information to RCU CPU stall
	warnings, also decrease from 60 seconds to 21 seconds.

hotplug.2012.11.08a: Minor updates to CPU hotplug handling.

tracing.2012.11.08a: Improved debugfs tracing, courtesy of Michael Wang.

idle.2012.10.24a: Updates to RCU idle/adaptive-idle handling, including
	a boot parameter that maps normal grace periods to expedited.

Resolved conflict in kernel/rcutree.c due to side-by-side change.

rcu: Clarify memory-ordering properties of grace-period primitives

2012-11-13T22:08:23+00:00

This commit explicitly states the memory-ordering properties of the
RCU grace-period primitives.  Although these properties were in some
sense implied by the fundmental property of RCU ("a grace period must
wait for all pre-existing RCU read-side critical sections to complete"),
stating it explicitly will be a great labor-saving device.

Reported-by: Oleg Nesterov 
Signed-off-by: Paul E. McKenney 
Reviewed-by: Oleg Nesterov

rcu: Remove rcu_switch()

2012-10-23T21:54:06+00:00

It's only there to call rcu_user_hooks_switch(). Let's
just call rcu_user_hooks_switch() directly, we don't need this
function in the middle.

Signed-off-by: Frederic Weisbecker 
Cc: Josh Triplett 
Cc: Peter Zijlstra 
Cc: Richard Weinberger 
Signed-off-by: Paul E. McKenney

rcu: Switch task's syscall hooks on context switch

2012-09-26T13:47:02+00:00

Clear the syscalls hook of a task when it's scheduled out so that if
the task migrates, it doesn't run the syscall slow path on a CPU
that might not need it.

Also set the syscalls hook on the next task if needed.

Signed-off-by: Frederic Weisbecker 
Cc: Alessio Igor Bogani 
Cc: Andrew Morton 
Cc: Avi Kivity 
Cc: Chris Metcalf 
Cc: Christoph Lameter 
Cc: Geoff Levand 
Cc: Gilad Ben Yossef 
Cc: Hakan Akkan 
Cc: H. Peter Anvin 
Cc: Ingo Molnar 
Cc: Josh Triplett 
Cc: Kevin Hilman 
Cc: Max Krasnyansky 
Cc: Peter Zijlstra 
Cc: Stephen Hemminger 
Cc: Steven Rostedt 
Cc: Sven-Thorsten Dietrich 
Cc: Thomas Gleixner 
Signed-off-by: Paul E. McKenney 
Reviewed-by: Josh Triplett

rcu: Settle config for userspace extended quiescent state

2012-09-26T13:44:04+00:00

Create a new config option under the RCU menu that put
CPUs under RCU extended quiescent state (as in dynticks
idle mode) when they run in userspace. This require
some contribution from architectures to hook into kernel
and userspace boundaries.

Signed-off-by: Frederic Weisbecker 
Cc: Alessio Igor Bogani 
Cc: Andrew Morton 
Cc: Avi Kivity 
Cc: Chris Metcalf 
Cc: Christoph Lameter 
Cc: Geoff Levand 
Cc: Gilad Ben Yossef 
Cc: Hakan Akkan 
Cc: H. Peter Anvin 
Cc: Ingo Molnar 
Cc: Josh Triplett 
Cc: Kevin Hilman 
Cc: Max Krasnyansky 
Cc: Peter Zijlstra 
Cc: Stephen Hemminger 
Cc: Steven Rostedt 
Cc: Sven-Thorsten Dietrich 
Cc: Thomas Gleixner 
Signed-off-by: Paul E. McKenney 
Reviewed-by: Josh Triplett

rcu: New rcu_user_enter_after_irq() and rcu_user_exit_after_irq() APIs

2012-09-26T13:44:01+00:00

In some cases, it is necessary to enter or exit userspace-RCU-idle mode
from an interrupt handler, for example, if some other CPU sends this
CPU a resched IPI.  In this case, the current CPU would enter the IPI
handler in userspace-RCU-idle mode, but would need to exit the IPI handler
after having exited that mode.

To allow this to work, this commit adds two new APIs to TREE_RCU:

- rcu_user_enter_after_irq(). This must be called from an interrupt between
rcu_irq_enter() and rcu_irq_exit().  After the irq calls rcu_irq_exit(),
the irq handler will return into an RCU extended quiescent state.
In theory, this interrupt is never a nested interrupt, but in practice
it might interrupt softirq, which looks to RCU like a nested interrupt.

- rcu_user_exit_after_irq(). This must be called from a non-nesting
interrupt, interrupting an RCU extended quiescent state, also
between rcu_irq_enter() and rcu_irq_exit(). After the irq calls
rcu_irq_exit(), the irq handler will return in an RCU non-quiescent
state.

[ Combined with "Allow calls to rcu_exit_user_irq from nesting irqs." ]

Signed-off-by: Frederic Weisbecker 
Signed-off-by: Paul E. McKenney 
Reviewed-by: Josh Triplett

rcu: New rcu_user_enter() and rcu_user_exit() APIs

2012-09-26T13:43:50+00:00

RCU currently insists that only idle tasks can enter RCU idle mode, which
prohibits an adaptive tickless kernel (AKA nohz cpusets), which in turn
would mean that usermode execution would always take scheduling-clock
interrupts, even when there is only one task runnable on the CPU in
question.

This commit therefore adds rcu_user_enter() and rcu_user_exit(), which
allow non-idle tasks to enter RCU idle mode.  These are quite similar
to rcu_idle_enter() and rcu_idle_exit(), respectively, except that they
omit the idle-task checks.

[ Updated to use "user" flag rather than separate check functions. ]

[ paulmck: Updated to drop exports of new functions based on Josh's patch
  getting rid of the need for them. ]

Signed-off-by: Frederic Weisbecker 
Signed-off-by: Paul E. McKenney 
Cc: Alessio Igor Bogani 
Cc: Andrew Morton 
Cc: Avi Kivity 
Cc: Chris Metcalf 
Cc: Christoph Lameter 
Cc: Daniel Lezcano 
Cc: Geoff Levand 
Cc: Gilad Ben Yossef 
Cc: Hakan Akkan 
Cc: Ingo Molnar 
Cc: Kevin Hilman 
Cc: Max Krasnyansky 
Cc: Peter Zijlstra 
Cc: Stephen Hemminger 
Cc: Steven Rostedt 
Cc: Sven-Thorsten Dietrich 
Cc: Thomas Gleixner 
Reviewed-by: Josh Triplett

rcu: Permit RCU_NONIDLE() to be used from interrupt context

2012-09-23T14:42:49+00:00

There is a need to use RCU from interrupt context, but either before
rcu_irq_enter() is called or after rcu_irq_exit() is called.  If the
interrupt occurs from idle, then lockdep-RCU will complain about such
uses, as they appear to be illegal uses of RCU from the idle loop.
In other environments, RCU_NONIDLE() could be used to properly protect
the use of RCU, but RCU_NONIDLE() currently cannot be invoked except
from process context.

This commit therefore modifies RCU_NONIDLE() to permit its use more
globally.

Reported-by: Steven Rostedt 
Signed-off-by: Paul E. McKenney 
Signed-off-by: Paul E. McKenney

rcu: Fix broken strings in RCU's source code.

2012-07-06T13:01:49+00:00

Although the C language allows you to break strings across lines, doing
this makes it hard for people to find the Linux kernel code corresponding
to a given console message.  This commit therefore fixes broken strings
throughout RCU's source code.

Suggested-by: Josh Triplett 
Suggested-by: Ingo Molnar 
Signed-off-by: Paul E. McKenney