Lin Ming reported a 10% OLTP regression against 2.6.27-rc4.

The difference seems to come from different preemption agressiveness,
which affects the cache footprint of the workload and its effective
cache trashing.

Aggresively preempt a task if its avg overlap is very small, this should
avoid the task going to sleep and find it still running when we schedule
back to it - saving a wakeup.
Reported-by: NLin Ming <ming.m.lin@intel.com>
Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Spencer reported a problem where utime and stime were going negative despite
the fixes in commit b27f03d4. The suspected
reason for the problem is that signal_struct maintains it's own utime and
stime (of exited tasks), these are not updated using the new task_utime()
routine, hence sig->utime can go backwards and cause the same problem
to occur (sig->utime, adds tsk->utime and not task_utime()). This patch
fixes the problem

TODO: using max(task->prev_utime, derived utime) works for now, but a more
generic solution is to implement cputime_max() and use the cputime_gt()
function for comparison.

Reported-by: spencer@bluehost.com
Signed-off-by: NBalbir Singh <balbir@linux.vnet.ibm.com>
Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

remove 8 bytes of padding on 64 bit builds
(also removes 8 bytes from task_struct)
Signed-off-by: NRichard Kennedy <richard@rsk.demon.co.uk>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

reorder structure to remove 8 bytes of padding on 64 bit builds
Signed-off-by: NRichard Kennedy <richard@rsk.demon.co.uk>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

The patches that are intended to introduce copy-on-write credentials for 2.6.28
require abstraction of access to some fields of the task structure,
particularly for the case of one task accessing another's credentials where RCU
will have to be observed.

Introduced here are trivial no-op versions of the desired accessors for current
and other tasks so that other subsystems can start to be converted over more
easily.

Wrappers are introduced into a new header (linux/cred.h) for UID/GID,
EUID/EGID, SUID/SGID, FSUID/FSGID, cap_effective and current's subscribed
user_struct.  These wrappers are macros because the ordering between header
files mitigates against making them inline functions.

linux/cred.h is #included from linux/sched.h.

Further, XFS is modified such that it no longer defines and uses parameterised
versions of current_fs[ug]id(), thus getting rid of the namespace collision
otherwise incurred.
Signed-off-by: NDavid Howells <dhowells@redhat.com>
Signed-off-by: NJames Morris <jmorris@namei.org>

Some arch's can't handle sched_clock() being called too early - delay
this until sched_clock_init() has been called.
Reported-by: NBill Gatliff <bgat@billgatliff.com>
Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Tested-by: NNishanth Aravamudan <nacc@us.ibm.com>
CC: Russell King - ARM Linux <linux@arm.linux.org.uk>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Found an interactivity problem on a quad core test-system - simple
CPU loops would occasionally delay the system un an unacceptable way.

After much debugging with Peter Zijlstra it turned out that the problem
is caused by the string of sched_clock() changes - they caused the CPU
clock to jump backwards a bit - which confuses the scheduler arithmetics.

(which is unsigned for performance reasons)

So revert:

 # c300ba25: sched_clock: and multiplier for TSC to gtod drift
 # c0c8773: sched_clock: only update deltas with local reads.
 # af52a90a: sched_clock: stop maximum check on NO HZ
 # f7cce27f: sched_clock: widen the max and min time

This solves the interactivity problems.
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Acked-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: NMike Galbraith <efault@gmx.de>

Simplify the code of include/linux/task_io_accounting.h.

It is also more reasonable to have all the task i/o-related statistics in a
single struct (task_io_accounting).
Signed-off-by: NAndrea Righi <righi.andrea@gmail.com>
Signed-off-by: NOleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Put all i/o statistics in struct proc_io_accounting and use inline functions to
initialize and increment statistics, removing a lot of single variable
assignments.

This also reduces the kernel size as following (with CONFIG_TASK_XACCT=y and
CONFIG_TASK_IO_ACCOUNTING=y).

    text    data     bss     dec     hex filename
   11651       0       0   11651    2d83 kernel/exit.o.before
   11619       0       0   11619    2d63 kernel/exit.o.after
   10886     132     136   11154    2b92 kernel/fork.o.before
   10758     132     136   11026    2b12 kernel/fork.o.after

 3082029  807968 4818600 8708597  84e1f5 vmlinux.o.before
 3081869  807968 4818600 8708437  84e155 vmlinux.o.after
Signed-off-by: NAndrea Righi <righi.andrea@gmail.com>
Acked-by: NOleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

This extends wait_task_inactive() with a new argument so it can be used in
a "soft" mode where it will check for the task changing state unexpectedly
and back off.  There is no change to existing callers.  This lays the
groundwork to allow robust, noninvasive tracing that can try to sample a
blocked thread but back off safely if it wakes up.
Signed-off-by: NRoland McGrath <roland@redhat.com>
Cc: Oleg Nesterov <oleg@tv-sign.ru>
Reviewed-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

This moves the ptrace logic in task death (exit_notify) into tracehook.h
inlines.  Some code is rearranged slightly to make things nicer.  There is
no change, only cleanup.

There is one hook called with the tasklist_lock write-locked, as ptrace
needs.  There is also a new hook called after exit_state changes and
without locks.  This is a better place for tracing work to be in the
future, since it doesn't delay the whole system with locking.
Signed-off-by: NRoland McGrath <roland@redhat.com>
Cc: Oleg Nesterov <oleg@tv-sign.ru>
Reviewed-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

A previous patch added the early_initcall(), to allow a cleaner hooking of
pre-SMP initcalls.  Now we remove the older interface, converting all
existing users to the new one.

[akpm@linux-foundation.org: cleanups]
[akpm@linux-foundation.org: build fix]
[kosaki.motohiro@jp.fujitsu.com: warning fix]
[kosaki.motohiro@jp.fujitsu.com: warning fix]
Signed-off-by: NEduard - Gabriel Munteanu <eduard.munteanu@linux360.ro>
Cc: Tom Zanussi <tzanussi@gmail.com>
Signed-off-by: NKOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Fix this, on avr32:

  include/linux/utsname.h:35,
                   from init/main.c:20:
  include/linux/sched.h: In function 'arch_pick_mmap_layout':
  include/linux/sched.h:2149: error: implicit declaration of function 'PAGE_ALIGN'
Reported-by: NAdrian Bunk <bunk@kernel.org>
Cc: Haavard Skinnemoen <hskinnemoen@atmel.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Sometimes, application responses become bad under heavy memory load.
Applications take a bit time to reclaim memory.  The statistics, how long
memory reclaim takes, will be useful to measure memory usage.

This patch adds accounting memory reclaim to per-task-delay-accounting for
accounting the time of do_try_to_free_pages().

<i.e>

- When System is under low memory load,
  memory reclaim may not occur.

$ free
             total       used       free     shared    buffers     cached
Mem:       8197800    1577300    6620500          0       4808    1516724
-/+ buffers/cache:      55768    8142032
Swap:     16386292          0   16386292

$ vmstat 1
procs -----------memory---------- ---swap-- -----io---- -system-- ----cpu----
 r  b   swpd   free   buff  cache   si   so    bi    bo   in   cs us sy id wa
 0  0      0 5069748  10612 3014060    0    0     0     0    3   26  0  0 100  0
 0  0      0 5069748  10612 3014060    0    0     0     0    4   22  0  0 100  0
 0  0      0 5069748  10612 3014060    0    0     0     0    3   18  0  0 100  0

Measure the time of tar command.

$ ls -s test.dat
1501472 test.dat

$ time tar cvf test.tar test.dat
real    0m13.388s
user    0m0.116s
sys     0m5.304s

$ ./delayget -d -p <pid>
CPU             count     real total  virtual total    delay total
                  428     5528345500     5477116080       62749891
IO              count    delay total
                  338     8078977189
SWAP            count    delay total
                    0              0
RECLAIM         count    delay total
                    0              0

- When system is under heavy memory load
  memory reclaim may occur.

$ vmstat 1
procs -----------memory---------- ---swap-- -----io---- -system-- ----cpu----
 r  b   swpd   free   buff  cache   si   so    bi    bo   in   cs us sy id wa
 0  0 7159032  49724   1812   3012    0    0     0     0    3   24  0  0 100  0
 0  0 7159032  49724   1812   3012    0    0     0     0    4   24  0  0 100  0
 0  0 7159032  49848   1812   3012    0    0     0     0    3   22  0  0 100  0

In this case, one process uses more 8G memory
by execution of malloc() and memset().

$ time tar cvf test.tar test.dat
real    1m38.563s        <-  increased by 85 sec
user    0m0.140s
sys     0m7.060s

$ ./delayget -d -p <pid>
CPU             count     real total  virtual total    delay total
                 9021     7140446250     7315277975      923201824
IO              count    delay total
                 8965    90466349669
SWAP            count    delay total
                    3       21036367
RECLAIM         count    delay total
                  740    61011951153

In the later case, the value of RECLAIM is increasing.
So, taskstats can show how much memory reclaim influences TAT.
Signed-off-by: NKeika Kobayashi <kobayashi.kk@ncos.nec.co.jp>
Acked-by: NBalbir Singh <balbir@linux.vnet.ibm.com>
Acked-by: NKOSAKI Motohiro <kosaki.motohiro@jp.fujistu.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Report per-thread I/O statistics in /proc/pid/task/tid/io and aggregate
parent I/O statistics in /proc/pid/io.  This approach follows the same
model used to account per-process and per-thread CPU times.

As a practial application, this allows for example to quickly find the top
I/O consumer when a process spawns many child threads that perform the
actual I/O work, because the aggregated I/O statistics can always be found
in /proc/pid/io.

[ Oleg Nesterov points out that we should check that the task is still
  alive before we iterate over the threads, but also says that we can do
  that fixup on top of this later.  - Linus ]
Acked-by: NBalbir Singh <balbir@linux.vnet.ibm.com>
Signed-off-by: NAndrea Righi <righi.andrea@gmail.com>
Cc: Matt Heaton <matt@hostmonster.com>
Cc: Shailabh Nagar <nagar@watson.ibm.com>
Acked-by-with-comments: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Adapt acct_update_integrals() to include user time when calculating the time
difference.  The units of acct_rss_mem1 and acct_vm_mem1 are also changed from
pages-jiffies to pages-usecs to avoid calling jiffies_to_usecs() in
xacct_add_tsk() which might overflow.
Signed-off-by: NJonathan Lim <jlim@sgi.com>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

It seems to me that it was a mistake marking this function as deprecated
and scheduling it for removal, rather than resolutely removing it after
the last caller's death.

Anyway - better late, then never.
Signed-off-by: NPavel Emelyanov <xemul@openvz.org>
Cc: Oleg Nesterov <oleg@tv-sign.ru>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

This one had the only users so far - the kill_proc, which is removed, so
drop this (invalid in namespaced world) call too.

And of course - erase all references on it from comments.
Signed-off-by: NPavel Emelyanov <xemul@openvz.org>
Cc: Oleg Nesterov <oleg@tv-sign.ru>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

This function operated on a pid_t to kill a task, which is no longer valid
in a containerized system.

It has finally lost all its users and we can safely remove it from the
tree.
Signed-off-by: NPavel Emelyanov <xemul@openvz.org>
Cc: Oleg Nesterov <oleg@tv-sign.ru>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Kill PF_BORROWED_MM.  Change use_mm/unuse_mm to not play with ->flags, and
do s/PF_BORROWED_MM/PF_KTHREAD/ for a couple of other users.

No functional changes yet.  But this allows us to do further
fixes/cleanups.

oom_kill/ptrace/etc often check "p->mm != NULL" to filter out the
kthreads, this is wrong because of use_mm().  The problem with
PF_BORROWED_MM is that we need task_lock() to avoid races.  With this
patch we can check PF_KTHREAD directly, or use a simple lockless helper:

	/* The result must not be dereferenced !!! */
	struct mm_struct *__get_task_mm(struct task_struct *tsk)
	{
		if (tsk->flags & PF_KTHREAD)
			return NULL;
		return tsk->mm;
	}

Note also ecard_task().  It runs with ->mm != NULL, but it's the kernel
thread without PF_BORROWED_MM.
Signed-off-by: NOleg Nesterov <oleg@tv-sign.ru>
Cc: Roland McGrath <roland@redhat.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Introduce the new PF_KTHREAD flag to mark the kernel threads.  It is set
by INIT_TASK() and copied to the forked childs (we could set it in
kthreadd() along with PF_NOFREEZE instead).

daemonize() was changed as well.  In that case testing of PF_KTHREAD is
racy, but daemonize() is hopeless anyway.

This flag is cleared in do_execve(), before search_binary_handler().
Probably not the best place, we can do this in exec_mmap() or in
start_thread(), or clear it along with PF_FORKNOEXEC.  But I think this
doesn't matter in practice, and if do_execve() fails kthread should die
soon.
Signed-off-by: NOleg Nesterov <oleg@tv-sign.ru>
Cc: Roland McGrath <roland@redhat.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

ptrace_stop() has some complicated checks to prevent the scheduling in the
TASK_TRACED state with the pending SIGKILL, but these checks are racy, and
they depend on arch_ptrace_stop_needed().

This patch assumes that the traced task should die asap if it was killed by
SIGKILL, in that case schedule()->signal_pending_state() has no reason to
ignore the TASK_WAKEKILL part of TASK_TRACED, and we can kill this nasty
special case.

Note: do_exit()->ptrace_notify() is special, the killed task can already
dequeue SIGKILL at this point. Another indication that fatal_signal_pending()
is not exactly right.
Signed-off-by: NOleg Nesterov <oleg@tv-sign.ru>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Matthew Wilcox <matthew@wil.cx>
Cc: Roland McGrath <roland@redhat.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

lib/debugobjects.c has a function to test if an object is on the stack.
The block layer and ide needs it (they need to avoid DMA from/to stack
buffers).  This patch moves the function to include/linux/sched.h so that
everyone can use it.

lib/debugobjects.c uses current->stack but this patch uses a
task_stack_page() accessor, which is a preferable way to access the stack.
Signed-off-by: NFUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Cc: Christoph Lameter <cl@linux-foundation.org>
Cc: Andy Whitcroft <apw@shadowen.org>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

provide an empty partition_sched_domains() definition for the UP case:

 include/linux/cpuset.h: In function ‘rebuild_sched_domains':
 include/linux/cpuset.h:163: error: implicit declaration of function ‘partition_sched_domains'
Signed-off-by: NIngo Molnar <mingo@elte.hu>

ptrace no longer fiddles with the children/sibling links, and the
old ptrace_children list is gone.  Now ptrace, whether of one's own
children or another's via PTRACE_ATTACH, just uses the new ptraced
list instead.

There should be no user-visible difference that matters.  The only
change is the order in which do_wait() sees multiple stopped
children and stopped ptrace attachees.  Since wait_task_stopped()
was changed earlier so it no longer reorders the children list, we
already know this won't cause any new problems.
Signed-off-by: NRoland McGrath <roland@redhat.com>

The freezer currently attempts to distinguish kernel threads from
user space tasks by checking if their mm pointer is unset and it
does not send fake signals to kernel threads.  However, there are
kernel threads, mostly related to networking, that behave like
user space tasks and may want to be sent a fake signal to be frozen.

Introduce the new process flag PF_FREEZER_NOSIG that will be set
by default for all kernel threads and make the freezer only send
fake signals to the tasks having PF_FREEZER_NOSIG unset.  Provide
the set_freezable_with_signal() function to be called by the kernel
threads that want to be sent a fake signal for freezing.

This patch should not change the freezer's observable behavior.
Signed-off-by: NRafael J. Wysocki <rjw@sisk.pl>
Signed-off-by: NAndi Kleen <ak@linux.intel.com>
Acked-by: NPavel Machek <pavel@suse.cz>
Signed-off-by: NLen Brown <len.brown@intel.com>

Working with ftrace I would get large jumps of 11 millisecs or more with
the clock tracer. This killed the latencing timings of ftrace and also
caused the irqoff self tests to fail.

What was happening is with NO_HZ the idle would stop the jiffy counter and
before the jiffy counter was updated the sched_clock would have a bad
delta jiffies to compare with the gtod with the maximum.

The jiffies would stop and the last sched_tick would record the last gtod.
On wakeup, the sched clock update would compare the gtod + delta jiffies
(which would be zero) and compare it to the TSC. The TSC would have
correctly (with a stable TSC) moved forward several jiffies. But because the
jiffies has not been updated yet the clock would be prevented from moving
forward because it would appear that the TSC jumped too far ahead.

The clock would then virtually stop, until the jiffies are updated. Then
the next sched clock update would see that the clock was very much behind
since the delta jiffies is now correct. This would then jump the clock
forward by several jiffies.

This caused ftrace to report several milliseconds of interrupts off
latency at every resume from NO_HZ idle.

This patch adds hooks into the nohz code to disable the checking of the
maximum clock update when nohz is in effect. It resumes the max check
when nohz has updated the jiffies again.
Signed-off-by: NSteven Rostedt <srostedt@redhat.com>
Cc: Steven Rostedt <srostedt@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

We found that the affine wakeup code needs rather accurate load figures
to be effective. The trouble is that updating the load figures is fairly
expensive with group scheduling. Therefore ratelimit the updating.
Signed-off-by: NPeter Zijlstra <peterz@infradead.org>
Cc: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
Cc: Mike Galbraith <efault@gmx.de>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Keeping the aggregate on the first cpu of the sched domain has two problems:
 - it could collide between different sched domains on different cpus
 - it could slow things down because of the remote accesses
Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
Cc: Mike Galbraith <efault@gmx.de>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Try again..

Initial commit: 18d95a28
Revert: 6363ca57Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
Cc: Mike Galbraith <efault@gmx.de>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Hidehiro Kawai noticed that sched_setscheduler() can fail in
stop_machine: it calls sched_setscheduler() from insmod, which can
have CAP_SYS_MODULE without CAP_SYS_NICE.

Two cases could have failed, so are changed to sched_setscheduler_nocheck:
  kernel/softirq.c:cpu_callback()
	- CPU hotplug callback
  kernel/stop_machine.c:__stop_machine_run()
	- Called from various places, including modprobe()
Signed-off-by: NRusty Russell <rusty@rustcorp.com.au>
Cc: Jeremy Fitzhardinge <jeremy@goop.org>
Cc: Hidehiro Kawai <hidehiro.kawai.ez@hitachi.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: linux-mm@kvack.org
Cc: sugita <yumiko.sugita.yf@hitachi.com>
Cc: Satoshi OSHIMA <satoshi.oshima.fk@hitachi.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Kthreads that have called kthread_bind() are bound to specific cpus, so
other tasks should not be able to change their cpus_allowed from under
them.  Otherwise, it is possible to move kthreads, such as the migration
or software watchdog threads, so they are not allowed access to the cpu
they work on.

Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Paul Menage <menage@google.com>
Cc: Paul Jackson <pj@sgi.com>
Signed-off-by: NDavid Rientjes <rientjes@google.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

schedule() has the special "TASK_INTERRUPTIBLE && signal_pending()" case,
this allows us to do

	current->state = TASK_INTERRUPTIBLE;
	schedule();

without fear to sleep with pending signal.

However, the code like

	current->state = TASK_KILLABLE;
	schedule();

is not right, schedule() doesn't take TASK_WAKEKILL into account. This means
that mutex_lock_killable(), wait_for_completion_killable(), down_killable(),
schedule_timeout_killable() can miss SIGKILL (and btw the second SIGKILL has
no effect).

Introduce the new helper, signal_pending_state(), and change schedule() to
use it. Hopefully it will have more users, that is why the task's state is
passed separately.

Note this "__TASK_STOPPED | __TASK_TRACED" check in signal_pending_state().
This is needed to preserve the current behaviour (ptrace_notify). I hope
this check will be removed soon, but this (afaics good) change needs the
separate discussion.

The fast path is "(state & (INTERRUPTIBLE | WAKEKILL)) + signal_pending(p)",
basically the same that schedule() does now. However, this patch of course
bloats schedule().
Signed-off-by: NOleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

The RT folks over at RedHat found an issue w.r.t. hotplug support which
was traced to problems with the cpupri infrastructure in the scheduler:

https://bugzilla.redhat.com/show_bug.cgi?id=449676

This bug affects 23-rt12+, 24-rtX, 25-rtX, and sched-devel.  This patch
applies to 25.4-rt4, though it should trivially apply to most cpupri enabled
kernels mentioned above.

It turned out that the issue was that offline cpus could get inadvertently
registered with cpupri so that they were erroneously selected during
migration decisions.  The end result would be an OOPS as the offline cpu
had tasks routed to it.

This patch generalizes the old join/leave domain interface into an
online/offline interface, and adjusts the root-domain/hotplug code to
utilize it.

I was able to easily reproduce the issue prior to this patch, and am no
longer able to reproduce it after this patch.  I can offline cpus
indefinately and everything seems to be in working order.

Thanks to Arnaldo (acme), Thomas, and Peter for doing the legwork to point
me in the right direction.  Also thank you to Peter for reviewing the
early iterations of this patch.
Signed-off-by: NGregory Haskins <ghaskins@novell.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>

This patch removes 24 bytes of padding and allows 1 extra object per
slab on my fedora based config.
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>

[ Stephen Rothwell <sfr@canb.auug.org.au>: build fix ]
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>

Yanmin Zhang reported:

Comparing with 2.6.25, volanoMark has big regression with kernel 2.6.26-rc1.
It's about 50% on my 8-core stoakley, 16-core tigerton, and Itanium Montecito.

With bisect, I located the following patch:

| 18d95a28 is first bad commit
| commit 18d95a28
| Author: Peter Zijlstra <a.p.zijlstra@chello.nl>
| Date:   Sat Apr 19 19:45:00 2008 +0200
|
|     sched: fair-group: SMP-nice for group scheduling

Revert it so that we get v2.6.25 behavior.
Bisected-by: NYanmin Zhang <yanmin_zhang@linux.intel.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Based on Roland's patch. This approach was suggested by Austin Clements
from the very beginning, and then by Linus.

As Austin pointed out, the execing task can be killed by SI_TIMER signal
because exec flushes the signal handlers, but doesn't discard the pending
signals generated by posix timers. Perhaps not a bug, but people find this
surprising. See http://bugzilla.kernel.org/show_bug.cgi?id=10460Signed-off-by: NOleg Nesterov <oleg@tv-sign.ru>
Cc: Austin Clements <amdragon+kernelbugzilla@mit.edu>
Cc: Roland McGrath <roland@redhat.com>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Fix unaligned access errors when setting softlockup_thresh on
64 bit platforms.

Allow softlockup detection to be disabled by setting
softlockup_thresh <= 0.

Detect that boot time softlockup detection has been disabled
earlier in softlockup_tick.
Signed-off-by: NDimitri Sivanich <sivanich@sgi.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>

allow users to configure the softlockup detector to generate a panic
instead of a warning message.

high-availability systems might opt for this strict method (combined
with panic_timeout= boot option/sysctl), instead of generating
softlockup warnings ad infinitum.

also, automated tests work better if the system reboots reliably (into
a safe kernel) in case of a lockup.

The full spectrum of configurability is supported: boot option, sysctl
option and Kconfig option.

it's default-disabled.
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>