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  1. 05 Feb, 2009 3 commits
    • Peter Zijlstra's avatar
      signal: re-add dead task accumulation stats. · 32bd671d
      Peter Zijlstra authored 
      We're going to split the process wide cpu accounting into two parts:

 - clocks; which can take all the time they want since they run
           from user context.

 - timers; which need constant time tracing but can affort the overhead
           because they're default off -- and rare.

The clock readout will go back to a full sum of the thread group, for this
we need to re-add the exit stats that were removed in the initial itimer
rework (f06febc9: timers: fix itimer/many thread hang).

Furthermore, since that full sum can be rather slow for large thread groups
and we have the complete dead task stats, revert the do_notify_parent time
computation.
Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
Reviewed-by: default avatarIngo Molnar <mingo@elte.hu>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
      32bd671d
    • Ingo Molnar's avatar
      Merge branch 'sched/urgent' into timers/urgent · 83895147
      Ingo Molnar authored 
      Merging it here because an upcoming timers/urgent fix relies on
a change already in sched/urgent and not yet upstream.
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
      83895147
    • Pavel Emelyanov's avatar
      x86: fix hpet timer reinit for x86_64 · a6a95406
      Pavel Emelyanov authored 
      There's a small problem with hpet_rtc_reinit function - it checks
for the:

	hpet_readl(HPET_COUNTER) - hpet_t1_cmp > 0

to continue increasing both the HPET_T1_CMP (register) and the
hpet_t1_cmp (variable).

But since the HPET_COUNTER is always 32-bit, if the hpet_t1_cmp
is 64-bit this condition will always be FALSE once the latter hits
the 32-bit boundary, and we can have a situation, when we don't
increase the HPET_T1_CMP register high enough.

The result - timer stops ticking, since HPET_T1_CMP becomes less,
than the COUNTER and never increased again.

The solution is (based on Linus's suggestion) to not compare 64-bits
(on 64-bit x86), but to do the comparison on 32-bit signed
integers.
Reported-by: default avatarKirill Korotaev <dev@openvz.org>
Signed-off-by: default avatarPavel Emelyanov <xemul@openvz.org>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
      a6a95406
  3. 04 Feb, 2009 1 commit
    • Suresh Siddha's avatar
      sched: fix nohz load balancer on cpu offline · 483b4ee6
      Suresh Siddha authored 
      Christian Borntraeger reports:

> After a logical cpu offline, even on a complete idle system, there
> is one cpu with full ticks. It turns out that nohz.cpu_mask has the
> the offlined cpu still set.
>
> In select_nohz_load_balancer() we check if the system is completely
> idle to turn of load balancing. We compare cpu_online_map with
> nohz.cpu_mask.  Since cpu_online_map is updated on cpu unplug,
> but nohz.cpu_mask is not, the check fails and the scheduler believes
> that we need an "idle load balancer" even on a fully idle system.
> Since the ilb cpu does not deactivate the timer tick this breaks NOHZ.

Fix the select_nohz_load_balancer() to not set the nohz.cpu_mask
while a cpu is going offline.
Reported-by: default avatarChristian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: default avatarSuresh Siddha <suresh.b.siddha@intel.com>
Tested-by: default avatarChristian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
      483b4ee6
  5. 03 Feb, 2009 12 commits
  7. 02 Feb, 2009 23 commits
  9. 01 Feb, 2009 1 commit
    • Linus Torvalds's avatar
      Manually revert "mlock: downgrade mmap sem while populating mlocked regions" · 27421e21
      Linus Torvalds authored 
      This essentially reverts commit 8edb08ca.

It downgraded our mmap semaphore to a read-lock while mlocking pages, in
order to allow other threads (and external accesses like "ps" et al) to
walk the vma lists and take page faults etc.  Which is a nice idea, but
the implementation does not work.

Because we cannot upgrade the lock back to a write lock without
releasing the mmap semaphore, the code had to release the lock entirely
and then re-take it as a writelock.  However, that meant that the caller
possibly lost the vma chain that it was following, since now another
thread could come in and mmap/munmap the range.

The code tried to work around that by just looking up the vma again and
erroring out if that happened, but quite frankly, that was just a buggy
hack that doesn't actually protect against anything (the other thread
could just have replaced the vma with another one instead of totally
unmapping it).

The only way to downgrade to a read map _reliably_ is to do it at the
end, which is likely the right thing to do: do all the 'vma' operations
with the write-lock held, then downgrade to a read after completing them
all, and then do the "populate the newly mlocked regions" while holding
just the read lock.  And then just drop the read-lock and return to user
space.

The (perhaps somewhat simpler) alternative is to just make all the
callers of mlock_vma_pages_range() know that the mmap lock got dropped,
and just re-grab the mmap semaphore if it needs to mlock more than one
vma region.

So we can do this "downgrade mmap sem while populating mlocked regions"
thing right, but the way it was done here was absolutely not correct.
Thus the revert, in the expectation that we will do it all correctly
some day.

Cc: Lee Schermerhorn <lee.schermerhorn@hp.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: stable@kernel.org
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      27421e21