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  1. 20 4月, 2008 16 次提交
  3. 26 3月, 2008 1 次提交
    • T
      NOHZ: reevaluate idle sleep length after add_timer_on() · 06d8308c
      由 Thomas Gleixner 提交于 
      add_timer_on() can add a timer on a CPU which is currently in a long
idle sleep, but the timer wheel is not reevaluated by the nohz code on
that CPU. So a timer can be delayed for quite a long time. This
triggered a false positive in the clocksource watchdog code.

To avoid this we need to wake up the idle CPU and enforce the
reevaluation of the timer wheel for the next timer event.

Add a function, which checks a given CPU for idle state, marks the
idle task with NEED_RESCHED and sends a reschedule IPI to notify the
other CPU of the change in the timer wheel.

Call this function from add_timer_on().
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
Acked-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: NIngo Molnar <mingo@elte.hu>
Cc: stable@kernel.org

--
 include/linux/sched.h |    6 ++++++
 kernel/sched.c        |   43 +++++++++++++++++++++++++++++++++++++++++++
 kernel/timer.c        |   10 +++++++++-
 3 files changed, 58 insertions(+), 1 deletion(-)
      06d8308c
  5. 21 3月, 2008 4 次提交
  7. 19 3月, 2008 2 次提交
    • I
      sched: wakeup-buddy tasks are cache-hot · f540a608
      由 Ingo Molnar 提交于 
      Wakeup-buddy tasks are cache-hot - this makes it a bit harder
for the load-balancer to tear them apart. (but it's still possible,
if the load is sufficiently assymetric)
Signed-off-by: NIngo Molnar <mingo@elte.hu>
      f540a608
    • I
      sched: improve affine wakeups · 4ae7d5ce
      由 Ingo Molnar 提交于 
      improve affine wakeups. Maintain the 'overlap' metric based on CFS's
sum_exec_runtime - which means the amount of time a task executes
after it wakes up some other task.

Use the 'overlap' for the wakeup decisions: if the 'overlap' is short,
it means there's strong workload coupling between this task and the
woken up task. If the 'overlap' is large then the workload is decoupled
and the scheduler will move them to separate CPUs more easily.

( Also slightly move the preempt_check within try_to_wake_up() - this has
  no effect on functionality but allows 'early wakeups' (for still-on-rq
  tasks) to be correctly accounted as well.)
Signed-off-by: NIngo Molnar <mingo@elte.hu>
      4ae7d5ce
  9. 15 3月, 2008 4 次提交
    • P
      sched: fix overload performance: buddy wakeups · aa2ac252
      由 Peter Zijlstra 提交于 
      Currently we schedule to the leftmost task in the runqueue. When the
runtimes are very short because of some server/client ping-pong,
especially in over-saturated workloads, this will cycle through all
tasks trashing the cache.

Reduce cache trashing by keeping dependent tasks together by running
newly woken tasks first. However, by not running the leftmost task first
we could starve tasks because the wakee can gain unlimited runtime.

Therefore we only run the wakee if its within a small
(wakeup_granularity) window of the leftmost task. This preserves
fairness, but does alternate server/client task groups.
Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
      aa2ac252
    • I
      sched: fix calc_delta_mine() · 27d11726
      由 Ingo Molnar 提交于 
      lw->weight can be 0 for a short time during bootup.
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
      27d11726
    • I
      sched: fix update_load_add()/sub() · e89996ae
      由 Ingo Molnar 提交于 
      Clear the cached inverse value when updating load. This is needed for
calc_delta_mine() to work correctly when using the rq load.
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
      e89996ae
    • H
      sched: fix race in schedule() · 0e1f3483
      由 Hiroshi Shimamoto 提交于 
      Fix a hard to trigger crash seen in the -rt kernel that also affects
the vanilla scheduler.

There is a race condition between schedule() and some dequeue/enqueue
functions; rt_mutex_setprio(), __setscheduler() and sched_move_task().

When scheduling to idle, idle_balance() is called to pull tasks from
other busy processor. It might drop the rq lock. It means that those 3
functions encounter on_rq=0 and running=1. The current task should be
put when running.

Here is a possible scenario:

   CPU0                               CPU1
    |                              schedule()
    |                              ->deactivate_task()
    |                              ->idle_balance()
    |                              -->load_balance_newidle()
rt_mutex_setprio()                     |
    |                              --->double_lock_balance()
    *get lock                          *rel lock
    * on_rq=0, ruuning=1               |
    * sched_class is changed           |
    *rel lock                          *get lock
    :                                  |
                                       :
                                   ->put_prev_task_rt()
                                   ->pick_next_task_fair()
                                       => panic

The current process of CPU1(P1) is scheduling. Deactivated P1, and the
scheduler looks for another process on other CPU's runqueue because CPU1
will be idle. idle_balance(), load_balance_newidle() and
double_lock_balance() are called and double_lock_balance() could drop
the rq lock. On the other hand, CPU0 is trying to boost the priority of
P1. The result of boosting only P1's prio and sched_class are changed to
RT. The sched entities of P1 and P1's group are never put. It makes
cfs_rq invalid, because the cfs_rq has curr and no leaf, but
pick_next_task_fair() is called, then the kernel panics.
Signed-off-by: NHiroshi Shimamoto <h-shimamoto@ct.jp.nec.com>
Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
      0e1f3483
  11. 11 3月, 2008 2 次提交
    • G
      keep rd->online and cpu_online_map in sync · 08f503b0
      由 Gregory Haskins 提交于 
      It is possible to allow the root-domain cache of online cpus to
become out of sync with the global cpu_online_map.  This is because we
currently trigger removal of cpus too early in the notifier chain.
Other DOWN_PREPARE handlers may in fact run and reconfigure the
root-domain topology, thereby stomping on our own offline handling.

The end result is that rd->online may become out of sync with
cpu_online_map, which results in potential task misrouting.

So change the offline handling to be more tightly coupled with the
global offline process by triggering on CPU_DYING intead of
CPU_DOWN_PREPARE.
Signed-off-by: NGregory Haskins <ghaskins@novell.com>
Cc: Gautham R Shenoy <ego@in.ibm.com>
Cc: "Siddha, Suresh B" <suresh.b.siddha@intel.com>
Cc: "Rafael J. Wysocki" <rjw@sisk.pl>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
      08f503b0
    • G
      Revert "cpu hotplug: adjust root-domain->online span in response to hotplug event" · 1f94ef59
      由 Gregory Haskins 提交于 
      This reverts commit 393d94d9.

Lets fix this right.
Signed-off-by: NGregory Haskins <ghaskins@novell.com>
Cc: Gautham R Shenoy <ego@in.ibm.com>
Cc: "Siddha, Suresh B" <suresh.b.siddha@intel.com>
Cc: "Rafael J. Wysocki" <rjw@sisk.pl>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
      1f94ef59
  13. 10 3月, 2008 1 次提交
  15. 07 3月, 2008 5 次提交
  17. 05 3月, 2008 1 次提交
    • P
      sched: revert load_balance_monitor() changes · 62fb1851
      由 Peter Zijlstra 提交于 
      The following commits cause a number of regressions:

  commit 58e2d4ca
  Author: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
  Date:   Fri Jan 25 21:08:00 2008 +0100
  sched: group scheduling, change how cpu load is calculated

  commit 6b2d7700
  Author: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
  Date:   Fri Jan 25 21:08:00 2008 +0100
  sched: group scheduler, fix fairness of cpu bandwidth allocation for task groups

Namely:
 - very frequent wakeups on SMP, reported by PowerTop users.
 - cacheline trashing on (large) SMP
 - some latencies larger than 500ms

While there is a mergeable patch to fix the latter, the former issues
are not fixable in a manner suitable for .25 (we're at -rc3 now).

Hence we revert them and try again in v2.6.26.
Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
CC: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
Tested-by: NAlexey Zaytsev <alexey.zaytsev@gmail.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
      62fb1851
  19. 25 2月, 2008 2 次提交
  21. 24 2月, 2008 2 次提交
    • L
      Add memory barrier semantics to wake_up() & co · 04e2f174
      由 Linus Torvalds 提交于 
      Oleg Nesterov and others have pointed out that on some architectures,
the traditional sequence of

	set_current_state(TASK_INTERRUPTIBLE);
	if (CONDITION)
		return;
	schedule();

is racy wrt another CPU doing

	CONDITION = 1;
	wake_up_process(p);

because while set_current_state() has a memory barrier separating
setting of the TASK_INTERRUPTIBLE state from reading of the CONDITION
variable, there is no such memory barrier on the wakeup side.

Now, wake_up_process() does actually take a spinlock before it reads and
sets the task state on the waking side, and on x86 (and many other
architectures) that spinlock is in fact equivalent to a memory barrier,
but that is not generally guaranteed.  The write that sets CONDITION
could move into the critical region protected by the runqueue spinlock.

However, adding a smp_wmb() to before the spinlock should now order the
writing of CONDITION wrt the lock itself, which in turn is ordered wrt
the accesses within the spinlock (which includes the reading of the old
state).

This should thus close the race (which probably has never been seen in
practice, but since smp_wmb() is a no-op on x86, it's not like this will
make anything worse either on the most common architecture where the
spinlock already gave the required protection).
Acked-by: NOleg Nesterov <oleg@tv-sign.ru>
Acked-by: NDmitry Adamushko <dmitry.adamushko@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      04e2f174
    • S
      kprobes: refuse kprobe insertion on add/sub_preempt_counter() · 43627582
      由 Srinivasa Ds 提交于 
      Kprobes makes use of preempt_disable(),preempt_enable_noresched() and these
functions inturn call add/sub_preempt_count().  So we need to refuse user from
inserting probe in to these functions.

This patch disallows user from probing add/sub_preempt_count().
Signed-off-by: NSrinivasa DS <srinivasa@in.ibm.com>
Acked-by: NAnanth N Mavinakayanahalli <ananth@in.ibm.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      43627582