linux-toradex.git/kernel/sched, branch v3.4.6

sched/nohz: Rewrite and fix load-avg computation -- again

2012-07-19T15:58:56+00:00

commit 5167e8d5417bf5c322a703d2927daec727ea40dd upstream.

Thanks to Charles Wang for spotting the defects in the current code:

 - If we go idle during the sample window -- after sampling, we get a
   negative bias because we can negate our own sample.

 - If we wake up during the sample window we get a positive bias
   because we push the sample to a known active period.

So rewrite the entire nohz load-avg muck once again, now adding
copious documentation to the code.

Reported-and-tested-by: Doug Smythies 
Reported-and-tested-by: Charles Wang 
Signed-off-by: Peter Zijlstra 
Cc: Linus Torvalds 
Cc: Andrew Morton 
Link: http://lkml.kernel.org/r/1340373782.18025.74.camel@twins
[ minor edits ]
Signed-off-by: Ingo Molnar 
Signed-off-by: Greg Kroah-Hartman

sched: Fix the relax_domain_level boot parameter

2012-06-17T18:21:28+00:00

commit a841f8cef4bb124f0f5563314d0beaf2e1249d72 upstream.

It does not get processed because sched_domain_level_max is 0 at the
time that setup_relax_domain_level() is run.

Simply accept the value as it is, as we don't know the value of
sched_domain_level_max until sched domain construction is completed.

Fix sched_relax_domain_level in cpuset.  The build_sched_domain() routine calls
the set_domain_attribute() routine prior to setting the sd->level, however,
the set_domain_attribute() routine relies on the sd->level to decide whether
idle load balancing will be off/on.

Signed-off-by: Dimitri Sivanich 
Signed-off-by: Peter Zijlstra 
Link: http://lkml.kernel.org/r/20120605184436.GA15668@sgi.com
Signed-off-by: Ingo Molnar 
Signed-off-by: Greg Kroah-Hartman

sched: Fix KVM and ia64 boot crash due to sched_groups circular linked list assumption

2012-05-09T10:27:35+00:00

If we have one cpu that failed to boot and boot cpu gave up on
waiting for it and then another cpu is being booted, kernel
might crash with following OOPS:

   BUG: unable to handle kernel NULL pointer dereference at 0000000000000018
   IP: [] __bitmap_weight+0x30/0x80
   Call Trace:
       [] build_sched_domains+0x7b6/0xa50

The crash happens in init_sched_groups_power() that expects
sched_groups to be circular linked list. However it is not
always true, since sched_groups preallocated in __sdt_alloc are
initialized in build_sched_groups and it may exit early

        if (cpu != cpumask_first(sched_domain_span(sd)))
                return 0;

without initializing sd->groups->next field.

Fix bug by initializing next field right after sched_group was
allocated.

Also-Reported-by: Jiang Liu 
Signed-off-by: Igor Mammedov 
Cc: a.p.zijlstra@chello.nl
Cc: pjt@google.com
Cc: seto.hidetoshi@jp.fujitsu.com
Link: http://lkml.kernel.org/r/1336559908-32533-1-git-send-email-imammedo@redhat.com
Signed-off-by: Ingo Molnar

sched: Fix OOPS when build_sched_domains() percpu allocation fails

2012-04-26T10:54:53+00:00

Under extreme memory used up situations, percpu allocation
might fail. We hit it when system goes to suspend-to-ram,
causing a kworker panic:

 EIP: [] build_sched_domains+0x23a/0xad0
 Kernel panic - not syncing: Fatal exception
 Pid: 3026, comm: kworker/u:3
 3.0.8-137473-gf42fbef #1

 Call Trace:
  [] panic+0x66/0x16c
  [...]
  [] partition_sched_domains+0x287/0x4b0
  [] cpuset_update_active_cpus+0x1fe/0x210
  [] cpuset_cpu_inactive+0x1d/0x30
  [...]

With this fix applied build_sched_domains() will return -ENOMEM and
the suspend attempt fails.

Signed-off-by: he, bo 
Reviewed-by: Zhang, Yanmin 
Reviewed-by: Srivatsa S. Bhat 
Signed-off-by: Peter Zijlstra 
Cc: Linus Torvalds 
Cc: Andrew Morton 
Cc: 
Link: http://lkml.kernel.org/r/1335355161.5892.17.camel@hebo
[ So, we fail to deallocate a CPU because we cannot allocate RAM :-/
  I don't like that kind of sad behavior but nevertheless it should
  not crash under high memory load. ]
Signed-off-by: Ingo Molnar

sched: Fix more load-balancing fallout

2012-04-26T10:54:52+00:00

Commits 367456c756a6 ("sched: Ditch per cgroup task lists for
load-balancing") and 5d6523ebd ("sched: Fix load-balance wreckage")
left some more wreckage.

By setting loop_max unconditionally to ->nr_running load-balancing
could take a lot of time on very long runqueues (hackbench!). So keep
the sysctl as max limit of the amount of tasks we'll iterate.

Furthermore, the min load filter for migration completely fails with
cgroups since inequality in per-cpu state can easily lead to such
small loads :/

Furthermore the change to add new tasks to the tail of the queue
instead of the head seems to have some effect.. not quite sure I
understand why.

Combined these fixes solve the huge hackbench regression reported by
Tim when hackbench is ran in a cgroup.

Reported-by: Tim Chen 
Acked-by: Tim Chen 
Signed-off-by: Peter Zijlstra 
Cc: Linus Torvalds 
Cc: Andrew Morton 
Link: http://lkml.kernel.org/r/1335365763.28150.267.camel@twins
[ got rid of the CONFIG_PREEMPT tuning and made small readability edits ]
Signed-off-by: Ingo Molnar

Merge branch 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2012-03-31T20:35:31+00:00

Pull scheduler fixes from Ingo Molnar.

* 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  sched: Fix incorrect usage of for_each_cpu_mask() in select_fallback_rq()
  sched: Fix __schedule_bug() output when called from an interrupt
  sched/arch: Introduce the finish_arch_post_lock_switch() scheduler callback

sched: Fix incorrect usage of for_each_cpu_mask() in select_fallback_rq()

2012-03-31T08:43:36+00:00

The function for_each_cpu_mask() expects a *pointer* to struct
cpumask as its second argument, whereas select_fallback_rq()
passes the value itself.

And moreover, for_each_cpu_mask() has been marked as obselete
in include/linux/cpumask.h. So move to the more appropriate
for_each_cpu() variant.

Reported-by: Sasha Levin 
Signed-off-by: Srivatsa S. Bhat 
Acked-by: Peter Zijlstra 
Cc: Dave Jones 
Cc: Liu Chuansheng 
Cc: vapier@gentoo.org
Cc: rusty@rustcorp.com.au
Link: http://lkml.kernel.org/r/4F75BED4.9050005@linux.vnet.ibm.com
Signed-off-by: Ingo Molnar

Merge branch 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2012-03-29T21:46:05+00:00

Pull scheduler fixes from Ingo Molnar.

* 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  cpusets: Remove an unused variable
  sched/rt: Improve pick_next_highest_task_rt()
  sched: Fix select_fallback_rq() vs cpu_active/cpu_online
  sched/x86/smp: Do not enable IRQs over calibrate_delay()
  sched: Fix compiler warning about declared inline after use
  MAINTAINERS: Update email address for SCHEDULER and PERF EVENTS

Merge branch 'sched/arch' into sched/urgent

2012-03-29T10:48:22+00:00

Merge reason: It has not gone upstream via the ARM tree, merge it via
              the scheduler tree.

Signed-off-by: Ingo Molnar

sched: Fix __schedule_bug() output when called from an interrupt

2012-03-29T06:34:45+00:00

If schedule is called from an interrupt handler __schedule_bug()
will call show_regs() with the registers saved during the
interrupt handling done in do_IRQ(). This means we'll see the
registers and the backtrace for the process that was interrupted
and not the full backtrace explaining who called schedule().

This is due to 838225b ("sched: use show_regs() to improve
__schedule_bug() output", 2007-10-24) which improperly assumed
that get_irq_regs() would return the registers for the current
stack because it is being called from within an interrupt
handler. Simply remove the show_reg() code so that we dump a
backtrace for the interrupt handler that called schedule().

[ I ran across this when I was presented with a scheduling while
  atomic log with a stacktrace pointing at spin_unlock_irqrestore().
  It made no sense and I had to guess what interrupt handler could
  be called and poke around for someone calling schedule() in an
  interrupt handler. A simple test of putting an msleep() in
  an interrupt handler works better with this patch because you
  can actually see the msleep() call in the backtrace. ]

Also-reported-by: Chris Metcalf 
Signed-off-by: Stephen Boyd 
Cc: Satyam Sharma 
Cc: Peter Zijlstra 
Link: http://lkml.kernel.org/r/1332979847-27102-1-git-send-email-sboyd@codeaurora.org
Signed-off-by: Ingo Molnar