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  1. Nov 16, 2007
    • Ingo Molnar's avatar
      sched: reorder SCHED_FEAT_ bits · 9612633a
      Ingo Molnar authored 
      

reorder SCHED_FEAT_ bits so that the used ones come first. Makes
tuning instructions easier.

Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
      9612633a
    • Adrian Bunk's avatar
      sched: make sched_nr_latency static · 518b22e9
      Adrian Bunk authored 
      

sched_nr_latency can now become static.

Signed-off-by: default avatarAdrian Bunk <bunk@kernel.org>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
      518b22e9
    • Dmitry Adamushko's avatar
      sched: remove activate_idle_task() · 94bc9a7b
      Dmitry Adamushko authored 
      

cpu_down() code is ok wrt sched_idle_next() placing the 'idle' task not
at the beginning of the queue.

So get rid of activate_idle_task() and make use of activate_task() instead.
It is the same as activate_task(), except for the update_rq_clock(rq) call
that is redundant.

Code size goes down:

   text    data     bss     dec     hex filename
  47853    3934     336   52123    cb9b sched.o.before
  47828    3934     336   52098    cb82 sched.o.after

Signed-off-by: default avatarDmitry Adamushko <dmitry.adamushko@gmail.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
      94bc9a7b
    • Dmitry Adamushko's avatar
      sched: fix __set_task_cpu() SMP race · ce96b5ac
      Dmitry Adamushko authored 
      

Grant Wilson has reported rare SCHED_FAIR_USER crashes on his quad-core
system, which crashes can only be explained via runqueue corruption.

there is a narrow SMP race in __set_task_cpu(): after ->cpu is set up to
a new value, task_rq_lock(p, ...) can be successfuly executed on another
CPU. We must ensure that updates of per-task data have been completed by
this moment.

this bug has been hiding in the Linux scheduler for an eternity (we never
had any explicit barrier for task->cpu in set_task_cpu() - so the bug was
introduced in 2.5.1), but only became visible via set_task_cfs_rq() being
accidentally put after the task->cpu update. It also probably needs a
sufficiently out-of-order CPU to trigger.

Reported-by: default avatarGrant Wilson <grant.wilson@zen.co.uk>
Signed-off-by: default avatarDmitry Adamushko <dmitry.adamushko@gmail.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
      ce96b5ac
    • Oleg Nesterov's avatar
      sched: fix SCHED_FIFO tasks & FAIR_GROUP_SCHED · dae51f56
      Oleg Nesterov authored 
      

Suppose that the SCHED_FIFO task does

	switch_uid(new_user);

Now, p->se.cfs_rq and p->se.parent both point into the old
user_struct->tg because sched_move_task() doesn't call set_task_cfs_rq()
for !fair_sched_class case.

Suppose that old user_struct/task_group is freed/reused, and the task
does

	sched_setscheduler(SCHED_NORMAL);

__setscheduler() sets fair_sched_class, but doesn't update
->se.cfs_rq/parent which point to the freed memory.

This means that check_preempt_wakeup() doing

		while (!is_same_group(se, pse)) {
			se = parent_entity(se);
			pse = parent_entity(pse);
		}

may OOPS in a similar way if rq->curr or p did something like above.

Perhaps we need something like the patch below, note that
__setscheduler() can't do set_task_cfs_rq().

Signed-off-by: default avatarOleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
      dae51f56
    • Christian Borntraeger's avatar
      sched: fix accounting of interrupts during guest execution on s390 · 9778385d
      Christian Borntraeger authored 
      

Currently the scheduler checks for PF_VCPU to decide if this timeslice
has to be accounted as guest time. On s390 host interrupts are not
disabled during guest execution. This causes theses interrupts to be
accounted as guest time if CONFIG_VIRT_CPU_ACCOUNTING is set. Solution
is to check if an interrupt triggered account_system_time. As the tick
is timer interrupt based, we have to subtract hardirq_offset.

I tested the patch on s390 with CONFIG_VIRT_CPU_ACCOUNTING and on
x86_64. Seems to work.

CC: Avi Kivity <avi@qumranet.com>
CC: Laurent Vivier <Laurent.Vivier@bull.net>
Signed-off-by: default avatarChristian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
      9778385d
  3. Nov 15, 2007