RCU tasklist_lock and RCU signal handling: send signals RCU-read-locked
instead of tasklist_lock read-locked.  This is a scalability improvement on
SMP and a preemption-latency improvement under PREEMPT_RCU.
Signed-off-by: NPaul E. McKenney <paulmck@us.ibm.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Acked-by: NWilliam Irwin <wli@holomorphy.com>
Cc: Roland McGrath <roland@redhat.com>
Cc: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

____cacheline_maxaligned_in_smp is currently used to align critical structures
and avoid false sharing.  It uses per-arch L1_CACHE_SHIFT_MAX and people find
L1_CACHE_SHIFT_MAX useless.

However, we have been using ____cacheline_maxaligned_in_smp to align
structures on the internode cacheline size.  As per Andi's suggestion,
following patch kills ____cacheline_maxaligned_in_smp and introduces
INTERNODE_CACHE_SHIFT, which defaults to L1_CACHE_SHIFT for all arches.
Arches needing L3/Internode cacheline alignment can define
INTERNODE_CACHE_SHIFT in the arch asm/cache.h.  Patch replaces
____cacheline_maxaligned_in_smp with ____cacheline_internodealigned_in_smp

With this patch, L1_CACHE_SHIFT_MAX can be killed
Signed-off-by: NRavikiran Thirumalai <kiran@scalex86.org>
Signed-off-by: NShai Fultheim <shai@scalex86.org>
Signed-off-by: NAndi Kleen <ak@suse.de>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Add a boolean "memory_migrate" to each cpuset, represented by a file
containing "0" or "1" in each directory below /dev/cpuset.

It defaults to false (file contains "0").  It can be set true by writing
"1" to the file.

If true, then anytime that a task is attached to the cpuset so marked, the
pages of that task will be moved to that cpuset, preserving, to the extent
practical, the cpuset-relative placement of the pages.

Also anytime that a cpuset so marked has its memory placement changed (by
writing to its "mems" file), the tasks in that cpuset will have their pages
moved to the cpusets new nodes, preserving, to the extent practical, the
cpuset-relative placement of the moved pages.
Signed-off-by: NPaul Jackson <pj@sgi.com>
Cc: Christoph Lameter <christoph@lameter.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

sys_migrate_pages implementation using swap based page migration

This is the original API proposed by Ray Bryant in his posts during the first
half of 2005 on linux-mm@kvack.org and linux-kernel@vger.kernel.org.

The intent of sys_migrate is to migrate memory of a process.  A process may
have migrated to another node.  Memory was allocated optimally for the prior
context.  sys_migrate_pages allows to shift the memory to the new node.

sys_migrate_pages is also useful if the processes available memory nodes have
changed through cpuset operations to manually move the processes memory.  Paul
Jackson is working on an automated mechanism that will allow an automatic
migration if the cpuset of a process is changed.  However, a user may decide
to manually control the migration.

This implementation is put into the policy layer since it uses concepts and
functions that are also needed for mbind and friends.  The patch also provides
a do_migrate_pages function that may be useful for cpusets to automatically
move memory.  sys_migrate_pages does not modify policies in contrast to Ray's
implementation.

The current code here is based on the swap based page migration capability and
thus is not able to preserve the physical layout relative to it containing
nodeset (which may be a cpuset).  When direct page migration becomes available
then the implementation needs to be changed to do a isomorphic move of pages
between different nodesets.  The current implementation simply evicts all
pages in source nodeset that are not in the target nodeset.

Patch supports ia64, i386 and x86_64.
Signed-off-by: NChristoph Lameter <clameter@sgi.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

swap migration's isolate_lru_page() currently uses an IPI to notify other
processors that the lru caches need to be drained if the page cannot be
found on the LRU.  The IPI interrupt may interrupt a processor that is just
processing lru requests and cause a race condition.

This patch introduces a new function run_on_each_cpu() that uses the
keventd() to run the LRU draining on each processor.  Processors disable
preemption when dealing the LRU caches (these are per processor) and thus
executing LRU draining from another process is safe.

Thanks to Lee Schermerhorn <lee.schermerhorn@hp.com> for finding this race
condition.
Signed-off-by: NChristoph Lameter <clameter@sgi.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

As recently there has been lot of traffic on the right values for batch and
high water marks for per_cpu_pagelists.  This patch makes these two
variables configurable through /proc interface.

A new tunable /proc/sys/vm/percpu_pagelist_fraction is added.  This entry
controls the fraction of pages at most in each zone that are allocated for
each per cpu page list.  The min value for this is 8.  It means that we
don't allow more than 1/8th of pages in each zone to be allocated in any
single per_cpu_pagelist.

The batch value of each per cpu pagelist is also updated as a result.  It
is set to pcp->high/4.  The upper limit of batch is (PAGE_SHIFT * 8)
Signed-off-by: NRohit Seth <rohit.seth@intel.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Add /proc/sys/vm/drop_caches.  When written to, this will cause the kernel to
discard as much pagecache and/or reclaimable slab objects as it can.  THis
operation requires root permissions.

It won't drop dirty data, so the user should run `sync' first.

Caveats:

a) Holds inode_lock for exorbitant amounts of time.

b) Needs to be taught about NUMA nodes: propagate these all the way through
   so the discarding can be controlled on a per-node basis.

This is a debugging feature: useful for getting consistent results between
filesystem benchmarks.  We could possibly put it under a config option, but
it's less than 300 bytes.
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

I've spent the past 3 days digging into a glibc testsuite failure in
current CVS, specifically libc/rt/tst-cputimer1.c The thr1 and thr2
timers fire too early in the second pass of this test.  The second
pass is noteworthy because it makes use of intervals, whereas the
first pass does not.

All throughout the posix-cpu-timers.c code, the calculation of the
process sched_time sum is implemented roughly as:

	unsigned long long sum;

	sum = tsk->signal->sched_time;
	t = tsk;
	do {
		sum += t->sched_time;
		t = next_thread(t);
	} while (t != tsk);

In fact this is the exact scheme used by check_process_timers().

In the case of check_process_timers(), current->sched_time has just
been updated (via scheduler_tick(), which is invoked by
update_process_times(), which subsequently invokes
run_posix_cpu_timers()) So there is no special processing necessary
wrt. that.

In other contexts, we have to allot for the fact that tsk->sched_time
might be a bit out of date if we are current.  And the
posix-cpu-timers.c code uses current_sched_time() to deal with that.

Unfortunately it does so in an erroneous and inconsistent manner in
one spot which is what results in the early timer firing.

In cpu_clock_sample_group_locked(), it does this:

		cpu->sched = p->signal->sched_time;
		/* Add in each other live thread.  */
		while ((t = next_thread(t)) != p) {
			cpu->sched += t->sched_time;
		}
		if (p->tgid == current->tgid) {
			/*
			 * We're sampling ourselves, so include the
			 * cycles not yet banked.  We still omit
			 * other threads running on other CPUs,
			 * so the total can always be behind as
			 * much as max(nthreads-1,ncpus) * (NSEC_PER_SEC/HZ).
			 */
			cpu->sched += current_sched_time(current);
		} else {
			cpu->sched += p->sched_time;
		}

The problem is the "p->tgid == current->tgid" test.  If "p" is
not current, and the tgids are the same, we will add the process
t->sched_time twice into cpu->sched and omit "p"'s sched_time
which is very very very wrong.

posix-cpu-timers.c has a helper function, sched_ns(p) which takes care
of this, so my fix is to use that here instead of this special tgid
test.

The fact that current can be one of the sub-threads of "p" points out
that we could make things a little bit more accurate, perhaps by using
sched_ns() on every thread we process in these loops.  It also points
out that we don't use the most accurate value for threads in the group
actively running other cpus (and this is mentioned in the comment).

But that is a future enhancement, and this fix here definitely makes
sense.
Signed-off-by: NDavid S. Miller <davem@davemloft.net>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

This patch fixes an issue reported by Coverity in kernel/module.c

Error reported: Cannot reach this line of code "else return ptr;"

Patch description:
  This is the error path, so 'err' will be negative, the else case
  is not required, this patch removes it.
Signed-off-by: NJayachandran C. <c.jayachandran@gmail.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Sanitize some s390 Kconfig options.  We have ARCH_S390, ARCH_S390X,
ARCH_S390_31, 64BIT, S390_SUPPORT and COMPAT.  Replace these 6 options by
S390, 64BIT and COMPAT.
Signed-off-by: NMartin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

There are some more places where the use of cputime_t instead of an integer
type and the associated macros is necessary for the virtual cputime accounting
on s390.  Affected are the s390 specific appldata code and BSD process
accounting.
Signed-off-by: NMartin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

This makes the swsusp_info structure become the header of the image in the
literal sense (ie.  it is saved to the swap and read before any other image
data with the help of the swsusp's swap map structure, so generally it is
treated in the same way as the rest of the image).

The main thing it does is to make swsusp_header contain the offset of the swap
map used to track the image data pages rather than the offset of swsusp_info.
 Simultaneously, swsusp_info becomes the first image page written to the swap.

The other changes are generally consequences of the above with a few
exceptions (there's some consolidation in the image reading part as a few
functions turn into trivial wrappers around something else).
Signed-off-by: NRafael J. Wysocki <rjw@sisk.pl>
Acked-by: NPavel Machek <pavel@suse.cz>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

This changes the handling of swap partitions by swsusp to avoid locking of the
swap devices that are not used for suspend and, consequently, simplifies the
code.
Signed-off-by: NRafael J. Wysocki <rjw@sisk.pl>
Acked-by: NPavel Machek <pavel@ucw.cz>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Make the suspend image size limit tunable via /sys/power/image_size.

It is necessary for systems on which there is a limited amount of swap
available for suspend.  It can also be useful for optimizing performance of
swsusp on systems with 1 GB of RAM or more.
Signed-off-by: NRafael J. Wysocki <rjw@sisk.pl>
Acked-by: NPavel Machek <pavel@ucw.cz>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Limit the size of the suspend image to approx.  500 MB, which should
improve the overall performance of swsusp on systems with more than 1 GB of
RAM.

It introduces the constant IMAGE_SIZE that can be set to the preferred size
of the image (in MB) and modifies the memory-shrinking part of swsusp to
take this constant into account (500 is the default value of IMAGE_SIZE).
Signed-off-by: NRafael J. Wysocki <rjw@sisk.pl>
Acked-by: NPavel Machek <pavel@ucw.cz>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

These two prototypes are already present in sched.h, remove duplicate
version.
Signed-off-by: NPavel Machek <pavel@suse.cz>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

This patch fixes a problem with the function enough_free_mem() used by
swsusp to verify if there is a sufficient number of memory pages available
to it to create and save the suspend image.

Namely, enough_free_mem() uses nr_free_pages() to obtain the number of free
memory pages, which is incorrect, because this function returns the total
number of free pages, including free highmem pages, and the highmem pages
cannot be used by swsusp for storing the image data.

The patch makes enough_free_mem() avoid counting the free highmem
pages as available to swsusp.
Signed-off-by: NRafael J. Wysocki <rjw@sisk.pl>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

This patch makes swsusp free only as much memory as needed to complete the
suspend and not as much as possible.   In the most of cases this should speed
up the suspend and make the system much more responsive after resume,
especially if a GUI (eg.  X Windows) is used.

If needed, the old behavior (ie to free as much memory as possible during
suspend) can be restored by unsetting FAST_FREE in power.h
Signed-off-by: NRafael J. Wysocki <rjw@sisk.pl>
Acked-by: NPavel Machek <pavel@suse.cz>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

This patch introduces the swap map structure that can be used by swsusp for
keeping tracks of data pages written to the swap.   The structure itself is
described in a comment within the patch.

The overall idea is to reduce the amount of metadata written to the swap and
to write and read the image pages sequentially, in a file-alike way.  This
makes the swap-handling part of swsusp fairly independent of its
snapshot-handling part and will hopefully allow us to completely separate
these two parts in the future.

This patch is needed to remove the suspend image size limit imposed by the
limited size of the swsusp_info structure, which is essential for x86-64
systems with more than 512 MB of RAM.
Signed-off-by: NRafael J. Wysocki <rjw@sisk.pl>
Acked-by: NPavel Machek <pavel@suse.cz>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

This patch removes the image encryption that is only used by swsusp instead of
zeroing the image after resume in order to prevent someone from reading some
confidential data from it in the future and it does not protect the image from
being read by an unauthorized person before resume.  The functionality it
provides should really belong to the user space and will possibly be
reimplemented after the swap-handling functionality of swsusp is moved to the
user space.
Signed-off-by: NRafael J. Wysocki <rjw@sisk.pl>
Acked-by: NPavel Machek <pavel@suse.cz>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Thanks to Christoph for doing most of the work.

This allows automatic SMP IRQ affinity assignment other than default "all
interrupts on all CPUs" which is rather expensive.  This might be useful if
the hardware can be programmed to distribute interrupts among different
CPUs, like Alpha does.
Signed-off-by: NIvan Kokshaysky <ink@jurassic.park.msu.ru>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Richard Henderson <rth@twiddle.net>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Make the futex code compilable and usable on NOMMU by making the attempt to
handle page faults conditional on CONFIG_MMU.  If this is not enabled, then
we can assume that EFAULT returned from futex_atomic_op_inuser() is not
recoverable, and that the address lies outside of valid memory.

handle_mm_fault() is made to BUG if called on NOMMU without attempting to
invoke the actual handler (__handle_mm_fault).
Signed-off-by: NDavid Howells <dhowells@redhat.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

- This function returns -EINVAL all the time.  Fix.

- Decruftify it a bit too.

- Writing to it doesn't seem to do what it's suppoed to do.

Cc: Pavel Machek <pavel@ucw.cz>
Cc: "Rafael J. Wysocki" <rjw@sisk.pl>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

lib/lib.a(kobject_uevent.o)(.text+0x25f): In function `kobject_uevent':
: undefined reference to `__alloc_skb'
lib/lib.a(kobject_uevent.o)(.text+0x2a1): In function `kobject_uevent':
: undefined reference to `skb_over_panic'
lib/lib.a(kobject_uevent.o)(.text+0x31d): In function `kobject_uevent':
: undefined reference to `skb_over_panic'
lib/lib.a(kobject_uevent.o)(.text+0x356): In function `kobject_uevent':
: undefined reference to `netlink_broadcast'
lib/lib.a(kobject_uevent.o)(.init.text+0x9): In function `kobject_uevent_init':
: undefined reference to `netlink_kernel_create'
make: *** [.tmp_vmlinux1] Error 1

Netlink is unconditionally enabled if CONFIG_NET, so that's OK.

kobject_uevent.o is compiled even if !CONFIG_HOTPLUG, which is lazy.

Let's compound the sin.
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

Leave the overloaded "hotplug" word to susbsystems which are handling
real devices. The driver core does not "plug" anything, it just exports
the state to userspace and generates events.
Signed-off-by: NKay Sievers <kay.sievers@suse.de>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

This deprecates the /proc/sys/kernel/hotplug file, as all
this stuff should be in /sys some day, right? :)
In /sys/kernel/ we have now uevent_seqnum and uevent_helper.
The seqnum is no longer used by udev, as the version for this
kernel depends on netlink which events will never get
out-of-order.

Recent udev versions disable the /sbin/hotplug helper with
an init script, cause it leads to OOM on big boxes by running
hundreds of shells in parallel. It should be done now by:
  echo "" > /sys/kernel/uevent_helper

(Note that "-n" does not work, cause neighter proc nor sysfs
support truncate().)
Signed-off-by: NKay Sievers <kay.sievers@suse.de>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

It makes zero sense to have hotplug, but not the netlink
events enabled today. Remove this option and merge the
kobject_uevent.h header into the kobject.h header file.
Signed-off-by: NKay Sievers <kay.sievers@suse.de>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

This patch removes all references to the bouncing address
rddunlap@osdl.org and one dead web page from the kernel.
Signed-off-by: NAdrian Bunk <bunk@stusta.de>
Acked-by: NRandy Dunlap <rdunlap@xenotime.net>

Signed-off-by: NSam Ravnborg <sam@ravnborg.org>

This is a slightly more complete fix for the previous minimal sysctl
string fix.  It always terminates the returned string with a NUL, even
if the full result wouldn't fit in the user-supplied buffer.

The returned length is the full untruncated length, so that you can
tell when truncation has occurred.
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

For the sysctl syscall, if the user wants to get the old value of a
sysctl entry and set a new value for it in the same syscall, the old
value is always overwritten by the new value if the sysctl entry is of
string type and if the user sets its strategy to sysctl_string.  This
issue lies in the strategy being run twice if the strategy is set to
sysctl_string, the general strategy sysctl_string always returns 0 if
success.

Such strategy routines as sysctl_jiffies and sysctl_jiffies_ms return 1
because they do read and write for the sysctl entry.

The strategy routine sysctl_string return 0 although it actually read
and write the sysctl entry.

According to my analysis, if a strategy routine do read and write, it
should return 1, if it just does some necessary check but not read and
write, it should return 0, for example sysctl_intvec.
Signed-off-by: NYi Yang <yang.y.yi@gmail.com>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

If the string was too long to fit in the user-supplied buffer,
the sysctl layer would zero-terminate it by writing past the
end of the buffer. Don't do that.

Noticed by Yi Yang <yang.y.yi@gmail.com>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Fix a memory ordering problem that occurs on IA64. The "store" to q->lock_ptr
in wake_futex() can become visible before wake_up_all() clears the lock in the
futex_q.
Signed-off-by: NJack Steiner <steiner@sgi.com>
Acked-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

All the work was done to setup the file and maintain the file handles but
the access functions were zeroed out due to the #ifdef.  Removing the
#ifdef allows full access to all the parameters when CONFIG_MODULES=n.

akpm: put it back again, but use CONFIG_SYSFS instead.
Signed-off-by: NJason Wessel <jason.wessel@windriver.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NAdrian Bunk <bunk@stusta.de>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

When multiple probes are registered at the same address and if due to some
recursion (probe getting triggered within a probe handler), we skip calling
pre_handlers and just increment nmissed field.

The below patch make sure it walks the list for multiple probes case.
Without the below patch we get incorrect results of nmissed count for
multiple probe case.
Signed-off-by: NAnil S Keshavamurthy <anil.s.keshavamurthy@intel.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

For Kprobes critical path is the path from debug break exception handler
till the control reaches kprobes exception code.  No probes can be
supported in this path as we will end up in recursion.

This patch prevents this by moving the below function to safe __kprobes
section onto which no probes can be inserted.
Signed-off-by: NAnil S Keshavamurthy <anil.s.keshavamurthy@intel.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

kauditd was causing suspends to fail because it refused to freeze.  Adding
a try_to_freeze() to its sleep loop solves the issue.
Signed-off-by: NPierre Ossman <drzeus@drzeus.cx>
Acked-by: NPavel Machek <pavel@suse.cz>
Cc: David Woodhouse <dwmw2@infradead.org>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

When registering multiple kprobes at the same address, we leave a small
window where the kprobe hlist will not contain a reference to the
registered kprobe, leading to potentially, a system crash if the breakpoint
is hit on another processor.

Patch below now automically relpace the old kprobe with the new
kprobe from the hash list.
Signed-off-by: NAnil S Keshavamurthy <anil.s.keshavamurthy@intel.com>
Acked-by: NAnanth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: "Paul E. McKenney" <paulmck@us.ibm.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

There are several functions that might seem appropriate for a timestamp:

get_cycles()
current_kernel_time()
do_gettimeofday()
<read jiffies/jiffies_64>

Each has problems with combinations of SMP-safety, low resolution, and
monotonicity. This patch adds a new function that returns a monotonic SMP-safe
timestamp with nanosecond resolution where available.

Changes:
	Split timestamp into separate patch
	Moved to kernel/time.c
	Renamed to getnstimestamp
	Fixed unintended-pointer-arithmetic bug
Signed-off-by: NMatt Helsley <matthltc@us.ibm.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Accessing nohz_cpu_mask before incrementing rcp->cur is racy.  It can cause
tickless idle CPUs to be included in rsp->cpumask, which will extend
graceperiods unnecessarily.

Fix this race.  It has been tested using extensions to RCU torture module
that forces various CPUs to become idle.
Signed-off-by: NSrivatsa Vaddagiri <vatsa@in.ibm.com>
Cc: Dipankar Sarma <dipankar@in.ibm.com>
Cc: "Paul E. McKenney" <paulmck@us.ibm.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>