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  1. 16 11月, 2007 3 次提交
    • D
      sched: fix __set_task_cpu() SMP race · ce96b5ac
      由 Dmitry Adamushko 提交于 
      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: NGrant Wilson <grant.wilson@zen.co.uk>
Signed-off-by: NDmitry Adamushko <dmitry.adamushko@gmail.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
      ce96b5ac
    • O
      sched: fix SCHED_FIFO tasks & FAIR_GROUP_SCHED · dae51f56
      由 Oleg Nesterov 提交于 
      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: NOleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
      dae51f56
    • C
      sched: fix accounting of interrupts during guest execution on s390 · 9778385d
      由 Christian Borntraeger 提交于 
      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: NChristian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
      9778385d
  3. 15 11月, 2007 37 次提交