16 Apr, 2009
1 commit
-
Don't try and predeclare inline funcs like this:
static inline void wait_migrated_callbacks(void)
...
static void _rcu_barrier(enum rcu_barrier type)
{
...
wait_migrated_callbacks();
}
...
static inline void wait_migrated_callbacks(void)
{
wait_event(rcu_migrate_wq, !atomic_read(&rcu_migrate_type_count));
}as it upsets some versions of gcc under some circumstances:
kernel/rcupdate.c: In function `_rcu_barrier':
kernel/rcupdate.c:125: sorry, unimplemented: inlining failed in call to 'wait_migrated_callbacks': function body not available
kernel/rcupdate.c:152: sorry, unimplemented: called from hereThis can be dealt with by simply putting the static variables (rcu_migrate_*)
at the top, and moving the implementation of the function up so that it
replaces its forward declaration.Signed-off-by: David Howells
Cc: Dipankar Sarma
Cc: Paul E. McKenney
Signed-off-by: Linus Torvalds
31 Mar, 2009
1 commit
-
cpu hotplug may happen asynchronously, some rcu callbacks are maybe
still on dead cpu, rcu_barrier() also needs to wait for these rcu
callbacks to complete, so we must ensure callbacks in dead cpu are
migrated to online cpu.Paul E. McKenney's review:
Good stuff, Lai!!! Simpler than any of the approaches that I was
considering, and, better yet, independent of the underlying RCU
implementation!!!I was initially worried that wake_up() might wake only one of two
possible wait_event()s, namely rcu_barrier() and the CPU_POST_DEAD code,
but the fact that wait_event() clears WQ_FLAG_EXCLUSIVE avoids that issue.
I was also worried about the fact that different RCU implementations have
different mappings of call_rcu(), call_rcu_bh(), and call_rcu_sched(), but
this is OK as well because we just get an extra (harmless) callback in the
case that they map together (for example, Classic RCU has call_rcu_sched()
mapping to call_rcu()).Overlap of CPU-hotplug operations is prevented by cpu_add_remove_lock,
and any stray callbacks that arrive (for example, from irq handlers
running on the dying CPU) either are ahead of the CPU_DYING callbacks on
the one hand (and thus accounted for), or happened after the rcu_barrier()
started on the other (and thus don't need to be accounted for).Signed-off-by: Lai Jiangshan
Reviewed-by: Paul E. McKenney
Cc: Peter Zijlstra
LKML-Reference:
Signed-off-by: Ingo Molnar
26 Feb, 2009
1 commit
-
This patch fixes a bug located by Vegard Nossum with the aid of
kmemcheck, updated based on review comments from Nick Piggin,
Ingo Molnar, and Andrew Morton. And cleans up the variable-name
and function-name language. ;-)The boot CPU runs in the context of its idle thread during boot-up.
During this time, idle_cpu(0) will always return nonzero, which will
fool Classic and Hierarchical RCU into deciding that a large chunk of
the boot-up sequence is a big long quiescent state. This in turn causes
RCU to prematurely end grace periods during this time.This patch changes the rcutree.c and rcuclassic.c rcu_check_callbacks()
function to ignore the idle task as a quiescent state until the
system has started up the scheduler in rest_init(), introducing a
new non-API function rcu_idle_now_means_idle() to inform RCU of this
transition. RCU maintains an internal rcu_idle_cpu_truthful variable
to track this state, which is then used by rcu_check_callback() to
determine if it should believe idle_cpu().Because this patch has the effect of disallowing RCU grace periods
during long stretches of the boot-up sequence, this patch also introduces
Josh Triplett's UP-only optimization that makes synchronize_rcu() be a
no-op if num_online_cpus() returns 1. This allows boot-time code that
calls synchronize_rcu() to proceed normally. Note, however, that RCU
callbacks registered by call_rcu() will likely queue up until later in
the boot sequence. Although rcuclassic and rcutree can also use this
same optimization after boot completes, rcupreempt must restrict its
use of this optimization to the portion of the boot sequence before the
scheduler starts up, given that an rcupreempt RCU read-side critical
section may be preeempted.In addition, this patch takes Nick Piggin's suggestion to make the
system_state global variable be __read_mostly.Changes since v4:
o Changes the name of the introduced function and variable to
be less emotional. ;-)Changes since v3:
o WARN_ON(nr_context_switches() > 0) to verify that RCU
switches out of boot-time mode before the first context
switch, as suggested by Nick Piggin.Changes since v2:
o Created rcu_blocking_is_gp() internal-to-RCU API that
determines whether a call to synchronize_rcu() is itself
a grace period.o The definition of rcu_blocking_is_gp() for rcuclassic and
rcutree checks to see if but a single CPU is online.o The definition of rcu_blocking_is_gp() for rcupreempt
checks to see both if but a single CPU is online and if
the system is still in early boot.This allows rcupreempt to again work correctly if running
on a single CPU after booting is complete.o Added check to rcupreempt's synchronize_sched() for there
being but one online CPU.Tested all three variants both SMP and !SMP, booted fine, passed a short
rcutorture test on both x86 and Power.Located-by: Vegard Nossum
Tested-by: Vegard Nossum
Tested-by: Paul E. McKenney
Signed-off-by: Paul E. McKenney
Signed-off-by: Ingo Molnar
05 Jan, 2009
1 commit
-
Impact: cleanup
Expand macro into two files.
The synchronize_rcu_xxx macro is quite ugly and it's only used by two
callers, so expand it instead. This makes this code easier to change.Signed-off-by: Andi Kleen
Signed-off-by: Paul E. McKenney
Signed-off-by: Ingo Molnar
21 Oct, 2008
1 commit
-
current rcu_barrier_bh() is like this:
void rcu_barrier_bh(void)
{
BUG_ON(in_interrupt());
/* Take cpucontrol mutex to protect against CPU hotplug */
mutex_lock(&rcu_barrier_mutex);
init_completion(&rcu_barrier_completion);
atomic_set(&rcu_barrier_cpu_count, 0);
/*
* The queueing of callbacks in all CPUs must be atomic with
* respect to RCU, otherwise one CPU may queue a callback,
* wait for a grace period, decrement barrier count and call
* complete(), while other CPUs have not yet queued anything.
* So, we need to make sure that grace periods cannot complete
* until all the callbacks are queued.
*/
rcu_read_lock();
on_each_cpu(rcu_barrier_func, (void *)RCU_BARRIER_BH, 1);
rcu_read_unlock();
wait_for_completion(&rcu_barrier_completion);
mutex_unlock(&rcu_barrier_mutex);
}The inconsistency of the code and the comments show a bug here.
rcu_read_lock() cannot make sure that "grace periods for RCU_BH
cannot complete until all the callbacks are queued".
it only make sure that race periods for RCU cannot complete
until all the callbacks are queued.so we must use rcu_read_lock_bh() for rcu_barrier_bh().
like this:void rcu_barrier_bh(void)
{
......
rcu_read_lock_bh();
on_each_cpu(rcu_barrier_func, (void *)RCU_BARRIER_BH, 1);
rcu_read_unlock_bh();
......
}and also rcu_barrier() rcu_barrier_sched() are implemented like this.
it will bring a lot of duplicate code. My patch uses another way to
fix this bug, please see the comment of my patch.
Thank Paul E. McKenney for he rewrote the comment.Signed-off-by: Lai Jiangshan
Reviewed-by: Paul E. McKenney
Signed-off-by: Ingo Molnar
21 Aug, 2008
1 commit
-
Fix RCU's synchronize_rcu() so that it looks like a C function, enabling
it to be recognized as a function with kernel-doc annotation.Warning(linux-2.6.26-git11//kernel/rcupdate.c:81): No description found for parameter 'synchronize_rcu'
Warning(linux-2.6.26-git11//kernel/rcupdate.c:81): No description found for parameter 'call_rcu'[akpm@linux-foundation.org: fix comment]
Signed-off-by: Randy Dunlap
Signed-off-by: Andrew Morton
Signed-off-by: Ingo Molnar
16 Jul, 2008
1 commit
-
…l/git/tip/linux-2.6-tip
* 'generic-ipi-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip: (22 commits)
generic-ipi: more merge fallout
generic-ipi: merge fix
x86, visws: use mach-default/entry_arch.h
x86, visws: fix generic-ipi build
generic-ipi: fixlet
generic-ipi: fix s390 build bug
generic-ipi: fix linux-next tree build failure
fix: "smp_call_function: get rid of the unused nonatomic/retry argument"
fix: "smp_call_function: get rid of the unused nonatomic/retry argument"
fix "smp_call_function: get rid of the unused nonatomic/retry argument"
on_each_cpu(): kill unused 'retry' parameter
smp_call_function: get rid of the unused nonatomic/retry argument
sh: convert to generic helpers for IPI function calls
parisc: convert to generic helpers for IPI function calls
mips: convert to generic helpers for IPI function calls
m32r: convert to generic helpers for IPI function calls
arm: convert to generic helpers for IPI function calls
alpha: convert to generic helpers for IPI function calls
ia64: convert to generic helpers for IPI function calls
powerpc: convert to generic helpers for IPI function calls
...Fix trivial conflicts due to rcu updates in kernel/rcupdate.c manually
26 Jun, 2008
1 commit
-
It's not even passed on to smp_call_function() anymore, since that
was removed. So kill it.Acked-by: Jeremy Fitzhardinge
Reviewed-by: Paul E. McKenney
Signed-off-by: Jens Axboe
19 May, 2008
2 commits
-
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 -
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
14 Feb, 2008
1 commit
-
This comment caused some consternation during fastcall removal. Make it
truthful.Signed-off-by: Paul E. McKenney
Cc: Harvey Harrison
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
26 Jan, 2008
3 commits
-
Fix rcu_barrier() to work properly in preemptive kernel environment.
Also, the ordering of callback must be preserved while moving
callbacks to another CPU during CPU hotplug.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 -
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 -
This patch makes RCU use softirq instead of tasklets.
It also adds a memory barrier after raising the softirq
inorder to ensure that the cpu sees the most recently updated
value of rcu->cur while processing callbacks.
The discussion of the related theoretical race pointed out
by James Huang can be found here --> http://lkml.org/lkml/2007/11/20/603Signed-off-by: Gautham R Shenoy
Signed-off-by: Steven Rostedt
Signed-off-by: Dipankar Sarma
Reviewed-by: Steven Rostedt
Signed-off-by: Ingo Molnar
23 Jan, 2008
1 commit
-
rcu_online_cpu() should be __cpuinit instead of __devinit.
WARNING: vmlinux.o(.text+0x4b6d5): Section mismatch: reference to .init.text: (between 'rcu_cpu_notify' and 'wakeme_after_rcu')
Signed-off-by: Randy Dunlap
Cc: Sam Ravnborg
Acked-by: Ingo Molnar
Cc: Thomas Gleixner
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
17 Oct, 2007
1 commit
-
This patch cleans up duplicate includes in
kernel/Signed-off-by: Jesper Juhl
Acked-by: Paul E. McKenney
Reviewed-by: Satyam Sharma
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
12 Oct, 2007
1 commit
-
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
10 May, 2007
1 commit
-
Since nonboot CPUs are now disabled after tasks and devices have been
frozen and the CPU hotplug infrastructure is used for this purpose, we need
special CPU hotplug notifications that will help the CPU-hotplug-aware
subsystems distinguish normal CPU hotplug events from CPU hotplug events
related to a system-wide suspend or resume operation in progress. This
patch introduces such notifications and causes them to be used during
suspend and resume transitions. It also changes all of the
CPU-hotplug-aware subsystems to take these notifications into consideration
(for now they are handled in the same way as the corresponding "normal"
ones).[oleg@tv-sign.ru: cleanups]
Signed-off-by: Rafael J. Wysocki
Cc: Gautham R Shenoy
Cc: Pavel Machek
Signed-off-by: Oleg Nesterov
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
08 Dec, 2006
1 commit
-
On some workloads, (for example when lot of close() syscalls are done), RCU
qlen can be quite large, and RCU heads are no longer in cpu cache when
rcu_do_batch() is called.This patch adds a prefetch() in rcu_do_batch() to give CPU a hint to bring
back cache lines containing 'struct rcu_head's.Most list manipulations macros include prefetch(), but not open coded ones
(at least with current C compilers :) )I got a nice speedup on a trivial benchmark (3.48 us per iteration instead
of 3.95 us on a 1.6 GHz Pentium-M)while (1) { pipe(p); close(fd[0]); close(fd[1]);}
Signed-off-by: Eric Dumazet
Cc: "Paul E. McKenney"
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
04 Oct, 2006
1 commit
-
Kill a hard-to-calculate 'rsinterval' boot parameter and per-cpu
rcu_data.last_rs_qlen. Instead, it adds adds a flag rcu_ctrlblk.signaled,
which records the fact that one of CPUs has sent a resched IPI since the
last rcu_start_batch().Roughly speaking, we need two rcu_start_batch()s in order to move callbacks
from ->nxtlist to ->donelist. This means that when ->qlen exceeds qhimark
and continues to grow, we should send a resched IPI, and then do it again
after we gone through a quiescent state.On the other hand, if it was already sent, we don't need to do it again
when another CPU detects overflow of the queue.Signed-off-by: Oleg Nesterov
Acked-by: Paul E. McKenney
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
13 Sep, 2006
1 commit
-
rcu_do_batch() decrements rdp->qlen with irqs enabled. This is not good,
it can also be modified by call_rcu() from interrupt.Decrement ->qlen once with irqs disabled, after a main loop.
Signed-off-by: Oleg Nesterov
Cc: Dipankar Sarma
Cc: "Paul E. McKenney"
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
01 Aug, 2006
1 commit
-
Few of the callback functions and notifier blocks that are associated with cpu
notifications incorrectly have __devinit and __devinitdata. They should be
__cpuinit and __cpuinitdata instead.It makes no functional difference but wastes text area when CONFIG_HOTPLUG is
enabled and CONFIG_HOTPLUG_CPU is not.This patch fixes all those instances.
Signed-off-by: Chandra Seetharaman
Cc: Ashok Raj
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
04 Jul, 2006
1 commit
-
Locking init improvement:
- introduce and use __SPIN_LOCK_UNLOCKED for array initializations,
to pass in the name string of locks, used by debuggingSigned-off-by: Ingo Molnar
Signed-off-by: Arjan van de Ven
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
28 Jun, 2006
3 commits
-
This patch reverts notifier_block changes made in 2.6.17
Signed-off-by: Chandra Seetharaman
Cc: Ashok Raj
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
In 2.6.17, there was a problem with cpu_notifiers and XFS. I provided a
band-aid solution to solve that problem. In the process, i undid all the
changes you both were making to ensure that these notifiers were available
only at init time (unless CONFIG_HOTPLUG_CPU is defined).We deferred the real fix to 2.6.18. Here is a set of patches that fixes the
XFS problem cleanly and makes the cpu notifiers available only at init time
(unless CONFIG_HOTPLUG_CPU is defined).If CONFIG_HOTPLUG_CPU is defined then cpu notifiers are available at run
time.This patch reverts the notifier_call changes made in 2.6.17
Signed-off-by: Chandra Seetharaman
Cc: Ashok Raj
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Add operations for the call_rcu_bh() variant of RCU. Also add an
rcu_batches_completed_bh() function, which is needed by rcutorture.Signed-off-by: Paul E. McKenney
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
23 Jun, 2006
1 commit
-
Remove synchronize_kernel() (deprecated 2-APR-2005 in
http://lkml.org/lkml/2005/4/3/11) and makes the RCU API inaccessible to
non-GPL Linux kernel modules (as was announced more than one year ago in
http://lkml.org/lkml/2005/4/3/8). Tested on x86 and ppc64.Signed-off-by: "Paul E. McKenney"
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
16 May, 2006
1 commit
-
With "Paul E. McKenney"
Introduce rcu_needs_cpu() interface. This can be used to tell if there
will be a new rcu batch on a cpu soon by looking at the curlist pointer.
This can be used to avoid to enter a tickless idle state where the cpu
would miss that a new batch is ready when rcu_start_batch would be called
on a different cpu.Signed-off-by: Heiko Carstens
Cc: "Paul E. McKenney"
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
26 Apr, 2006
2 commits
-
Few of the notifier_chain_register() callers use __init in the definition
of notifier_call. It is incorrect as the function definition should be
available after the initializations (they do not unregister them during
initializations).This patch fixes all such usages to _not_ have the notifier_call __init
section.Signed-off-by: Chandra Seetharaman
Signed-off-by: Linus Torvalds -
Few of the notifier_chain_register() callers use __devinitdata in the
definition of notifier_block data structure. It is incorrect as the
data structure should be available after the initializations (they do
not unregister them during initializations).This was leading to an oops when notifier_chain_register() call is
invoked for those callback chains after initialization.This patch fixes all such usages to _not_ have the notifier_block data
structure in the init data section.Signed-off-by: Chandra Seetharaman
Signed-off-by: Linus Torvalds
24 Mar, 2006
1 commit
-
__rcu_process_callbacks() disables interrupts to protect itself from
call_rcu() which adds new entries to ->nxtlist.However we can check "->nxtlist != NULL" with interrupts enabled, we can't
get "false positives" because call_rcu() can only change this condition
from 0 to 1.Tested with rcutorture.ko.
Signed-off-by: Oleg Nesterov
Acked-by: Dipankar Sarma
Cc: "Paul E. McKenney"
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
23 Mar, 2006
2 commits
-
This patch makes two needlessly global structs static.
Signed-off-by: Adrian Bunk
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Convert kernel/rcupdate's rcu_barrier_sema to mutex.
Signed-off-by: Ingo Molnar
Acked-by: "Paul E. McKenney"
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
21 Mar, 2006
1 commit
-
As the RCU symbols are going to be changed to GPL in the near future,
lets warn users that this is going to happen.Cc: Paul McKenney
Acked-by: Dipankar Sarma
Signed-off-by: Greg Kroah-Hartman
09 Mar, 2006
1 commit
-
This patch adds new tunables for RCU queue and finished batches. There are
two types of controls - number of completed RCU updates invoked in a batch
(blimit) and monitoring for high rate of incoming RCUs on a cpu (qhimark,
qlowmark).By default, the per-cpu batch limit is set to a small value. If the input
RCU rate exceeds the high watermark, we do two things - force quiescent
state on all cpus and set the batch limit of the CPU to INTMAX. Setting
batch limit to INTMAX forces all finished RCUs to be processed in one shot.
If we have more than INTMAX RCUs queued up, then we have bigger problems
anyway. Once the incoming queued RCUs fall below the low watermark, the
batch limit is set to the default.Signed-off-by: Dipankar Sarma
Cc: "Paul E. McKenney"
Cc: "David S. Miller"
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
11 Jan, 2006
2 commits
-
Pointed out by Srivatsa Vaddagiri .
rcu_do_batch() stops after processing maxbatch callbacks
on ->donelist leaving rcu_tasklet in TASKLET_STATE_SCHED
state.If CPU_DEAD event happens remaining ->donelist entries are
lost, rcu_offline_cpu() kills this tasklet.With this patch ->donelist migrates along with ->curlist
and ->nxtlist to the current cpu.Compile tested.
Signed-off-by: Oleg Nesterov
Acked-by: Paul E. McKenney
Cc: Srivatsa Vaddagiri
Cc: Dipankar Sarma
Signed-off-by: Linus Torvalds -
This patch moves rcu_state into the rcu_ctrlblk. I think there
are no reasons why we should have 2 different variables to control
rcu state. Every user of rcu_state has also "rcu_ctrlblk *rcp" in
the parameter list.Signed-off-by: Oleg Nesterov
Acked-by: Paul E. McKenney
Signed-off-by: Linus Torvalds
10 Jan, 2006
2 commits
-
I think it is better to set ->next_pending in the caller, when
it is needed. This saves one parameter, and this coincides with
cpu_quiet() beahaviour, which sets ->completed = ->cur itself.Signed-off-by: Oleg Nesterov
Acked-by: Paul E. McKenney
Signed-off-by: Linus Torvalds -
__rcu_pending() is rather fat and called twice from rcu_pending().
rcu_pending() has multiple callers, and not that small too.
This patch uninlines both of them.
Signed-off-by: Oleg Nesterov
Acked-by: Paul E. McKenney
Signed-off-by: Linus Torvalds
09 Jan, 2006
1 commit
-
Use atomic_inc_not_zero for rcu files instead of special case rcuref.
Signed-off-by: Nick Piggin
Cc: "Paul E. McKenney"
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
