linux-toradex.git/include/linux/rcupdate.h, branch v2.6.27.50

rcu: add rcu_barrier_sched() and rcu_barrier_bh()

2008-05-19T08:01:36+00:00

Add rcu_barrier_sched() and rcu_barrier_bh().  With these in place,
rcutorture no longer gives the occasional oops when repeatedly starting
and stopping torturing rcu_bh.  Also adds the API needed to flush out
pre-existing call_rcu_sched() callbacks.

Signed-off-by: Paul E. McKenney 
Signed-off-by: Mathieu Desnoyers 
Signed-off-by: Ingo Molnar 
Signed-off-by: Thomas Gleixner

rcu: add call_rcu_sched()

2008-05-19T08:01:36+00:00

Fourth cut of patch to provide the call_rcu_sched().  This is again to
synchronize_sched() as call_rcu() is to synchronize_rcu().

Should be fine for experimental and -rt use, but not ready for inclusion.
With some luck, I will be able to tell Andrew to come out of hiding on
the next round.

Passes multi-day rcutorture sessions with concurrent CPU hotplugging.

Fixes since the first version include a bug that could result in
indefinite blocking (spotted by Gautham Shenoy), better resiliency
against CPU-hotplug operations, and other minor fixes.

Fixes since the second version include reworking grace-period detection
to avoid deadlocks that could happen when running concurrently with
CPU hotplug, adding Mathieu's fix to avoid the softlockup messages,
as well as Mathieu's fix to allow use earlier in boot.

Fixes since the third version include a wrong-CPU bug spotted by
Andrew, getting rid of the obsolete synchronize_kernel API that somehow
snuck back in, merging spin_unlock() and local_irq_restore() in a
few places, commenting the code that checks for quiescent states based
on interrupting from user-mode execution or the idle loop, removing
some inline attributes, and some code-style changes.

Known/suspected shortcomings:

o	I still do not entirely trust the sleep/wakeup logic.  Next step
	will be to use a private snapshot of the CPU online mask in
	rcu_sched_grace_period() -- if the CPU wasn't there at the start
	of the grace period, we don't need to hear from it.  And the
	bit about accounting for changes in online CPUs inside of
	rcu_sched_grace_period() is ugly anyway.

o	It might be good for rcu_sched_grace_period() to invoke
	resched_cpu() when a given CPU wasn't responding quickly,
	but resched_cpu() is declared static...

This patch also fixes a long-standing bug in the earlier preemptable-RCU
implementation of synchronize_rcu() that could result in loss of
concurrent external changes to a task's CPU affinity mask.  I still cannot
remember who reported this...

Signed-off-by: Paul E. McKenney 
Signed-off-by: Mathieu Desnoyers 
Signed-off-by: Ingo Molnar 
Signed-off-by: Thomas Gleixner

rcupreempt: remove duplicate prototypes

2008-05-19T08:01:35+00:00

rcu_batches_completed and rcu_patches_completed_bh are both declared
in rcuclassic.h and rcupreempt.h. This patch removes the extra
prototypes for them from rcupdate.h.

rcu_batches_completed_bh is defined as a static inline in the rcupreempt.h
header file. Trying to export this as EXPORT_SYMBOL_GPL causes linking problems
with the powerpc linker. There's no need to export a static inlined function.

Modules must be compiled with the same type of RCU implementation as the
kernel they are for.

Signed-off-by: Steven Rostedt 
Signed-off-by: Ingo Molnar

Move ACCESS_ONCE() to

2008-05-11T02:51:16+00:00

It actually makes much more sense there, and we do tend to need it for
non-RCU usage too.  Moving it to  will allow some
other cases that have open-coded the same logic to use the same helper
function that RCU has used.

Signed-off-by: Linus Torvalds

Remove "#ifdef KERNEL" checks from unexported headers

2008-04-30T15:29:54+00:00

Remove the "#ifdef __KERNEL__" tests from unexported header files in
linux/include whose entire contents are wrapped in that preprocessor
test.

Signed-off-by: Robert P. J. Day 
Cc: David Woodhouse 
Cc: Sam Ravnborg 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

Remove rcu_assign_pointer() penalty for NULL pointers

2008-02-06T18:41:06+00:00

The rcu_assign_pointer() primitive currently unconditionally executes a
memory barrier, even when a NULL pointer is being assigned.  This has lead
some to avoid using rcu_assign_pointer() for NULL pointers, which loses the
self-documenting advantages of rcu_assign_pointer() This patch uses
__builtin_const_p() to omit needless memory barriers for NULL-pointer
assignments at compile time with no runtime penalty, as discussed in the
following thread:

	http://www.mail-archive.com/netdev@vger.kernel.org/msg54852.html

Tested on x86_64 and ppc64, also compiled the four cases (NULL/non-NULL
and const/non-const) with gcc version 4.1.2, and hand-checked the
assembly output.

Signed-off-by: Paul E. McKenney 
Acked-by: Herbert Xu 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

Preempt-RCU: implementation

2008-01-25T20:08:24+00:00

This patch implements a new version of RCU which allows its read-side
critical sections to be preempted. It uses a set of counter pairs
to keep track of the read-side critical sections and flips them
when all tasks exit read-side critical section. The details
of this implementation can be found in this paper -

	http://www.rdrop.com/users/paulmck/RCU/OLSrtRCU.2006.08.11a.pdf

and the article-

	http://lwn.net/Articles/253651/

This patch was developed as a part of the -rt kernel development and
meant to provide better latencies when read-side critical sections of
RCU don't disable preemption.  As a consequence of keeping track of RCU
readers, the readers have a slight overhead (optimizations in the paper).
This implementation co-exists with the "classic" RCU implementations
and can be switched to at compiler.

Also includes RCU tracing summarized in debugfs.

[ akpm@linux-foundation.org: build fixes on non-preempt architectures ]

Signed-off-by: Gautham R Shenoy 
Signed-off-by: Dipankar Sarma 
Signed-off-by: Paul E. McKenney 
Reviewed-by: Steven Rostedt 
Signed-off-by: Ingo Molnar

Preempt-RCU: reorganize RCU code into rcuclassic.c and rcupdate.c

2008-01-25T20:08:24+00:00

This patch re-organizes the RCU code to enable multiple implementations
of RCU. Users of RCU continues to include rcupdate.h and the
RCU interfaces remain the same. This is in preparation for
subsequently merging the preemptible RCU implementation.

Signed-off-by: Gautham R Shenoy 
Signed-off-by: Dipankar Sarma 
Signed-off-by: Paul E. McKenney 
Reviewed-by: Steven Rostedt 
Signed-off-by: Ingo Molnar

Immunize rcu_dereference() against crazy compiler writers

2007-10-17T15:42:46+00:00

Turns out that compiler writers are a bit more aggressive about optimizing
than one might expect.  This patch prevents a number of such optimizations
from messing up rcu_deference().  This is not merely a theoretical problem, as
evidenced by the rmb() in mce_log().

Signed-off-by: Paul E. McKenney 
Cc: Ingo Molnar 
Acked-by: Josh Triplett 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

lockdep: annotate rcu_read_{,un}lock{,_bh}

2007-10-11T20:11:12+00:00

lockdep annotate rcu_read_{,un}lock{,_bh} in order to catch imbalanced
usage.

Signed-off-by: Peter Zijlstra 
Signed-off-by: Ingo Molnar 
Cc: Paul E. McKenney

linux-toradex.git/include/linux/rcupdate.h, branch v2.6.27.50

rcu: add rcu_barrier_sched() and rcu_barrier_bh()

rcu: add call_rcu_sched()

rcupreempt: remove duplicate prototypes

Move ACCESS_ONCE() to

Remove "#ifdef __KERNEL__" checks from unexported headers

Remove rcu_assign_pointer() penalty for NULL pointers

Preempt-RCU: implementation

Preempt-RCU: reorganize RCU code into rcuclassic.c and rcupdate.c

Immunize rcu_dereference() against crazy compiler writers

lockdep: annotate rcu_read_{,un}lock{,_bh}

Remove "#ifdef KERNEL" checks from unexported headers