src/patches/suse-2.6.27.39/patches.fixes/fix-nr_uninterruptible-accounting-of-frozen-tasks

   1 From: Thomas Gleixner <tglx@linutronix.de>
   2 To: LKML <linux-kernel@vger.kernel.org>
   3 Cc: Andrew Morton <akpm@linux-foundation.org>, Rafael Wysocki <rjw@sisk.pl>, Ingo Molnar <mingo@elte.hu>, Peter Zijlstra <peterz@infradead.org>, Nathan Lynch <ntl@pobox.com>, Nigel Cunningham <nigel@tuxonice.net>, <stable@kernel.org>, containers@lists.linux-foundation.org, linux-pm@lists.linux-foundation.org, Matt Helsley <matthltc@us.ibm.com>
   4 Subject: [patch 2/2] sched: fix nr_uninterruptible accounting of frozen tasks really
   5 References: bnc#529660
   6
   7 commit e3c8ca8336 (sched: do not count frozen tasks toward load) broke
   8 the nr_uninterruptible accounting on freeze/thaw. On freeze the task
   9 is excluded from accounting with a check for (task->flags &
  10 PF_FROZEN), but that flag is cleared before the task is thawed. So
  11 while we prevent that the freezing task with state
  12 TASK_UNINTERRUPTIBLE is accounted to nr_uninterruptible we decrement
  13 nr_uninterruptible on thaw.
  14
  15 Use a separate flag which is handled by the freezing task itself. Set
  16 it before calling the scheduler with TASK_UNINTERRUPTIBLE state and
  17 clear it after we return from frozen state.
  18
  19 Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
  20 Cc: Nathan Lynch <ntl@pobox.com>
  21 Cc: Andrew Morton <akpm@linux-foundation.org>
  22 Cc: Nigel Cunningham <nigel@tuxonice.net>
  23 Cc: <stable@kernel.org>
  24 Cc: containers@lists.linux-foundation.org
  25 Cc: linux-pm@lists.linux-foundation.org
  26 Cc: Matt Helsley <matthltc@us.ibm.com>
  27 Acked-by: Jeff Mahoney <jeffm@suse.com>
  28 ---
  29  include/linux/sched.h |    3 ++-
  30  kernel/freezer.c      |    7 +++++++
  31  2 files changed, 9 insertions(+), 1 deletion(-)
  32
  33 --- a/include/linux/sched.h
  34 +++ b/include/linux/sched.h
  35 @@ -203,7 +203,7 @@ extern unsigned long long time_sync_thre
  36                         ((task->state & (__TASK_STOPPED | __TASK_TRACED)) != 0)
  37  #define task_contributes_to_load(task) \
  38                                 ((task->state & TASK_UNINTERRUPTIBLE) != 0 && \
  39 -                                (task->flags & PF_FROZEN) == 0)
  40 +                                (task->flags & PF_FREEZING) == 0)
  41
  42  #define __set_task_state(tsk, state_value)             \
  43         do { (tsk)->state = (state_value); } while (0)
  44 @@ -1507,6 +1507,7 @@ extern cputime_t task_gtime(struct task_
  45  #define PF_MEMALLOC    0x00000800      /* Allocating memory */
  46  #define PF_FLUSHER     0x00001000      /* responsible for disk writeback */
  47  #define PF_USED_MATH   0x00002000      /* if unset the fpu must be initialized before use */
  48 +#define PF_FREEZING    0x00004000      /* freeze in progress. do not account to load */
  49  #define PF_NOFREEZE    0x00008000      /* this thread should not be frozen */
  50  #define PF_FROZEN      0x00010000      /* frozen for system suspend */
  51  #define PF_FSTRANS     0x00020000      /* inside a filesystem transaction */
  52 --- a/kernel/freezer.c
  53 +++ b/kernel/freezer.c
  54 @@ -44,12 +44,19 @@ void refrigerator(void)
  55         recalc_sigpending(); /* We sent fake signal, clean it up */
  56         spin_unlock_irq(&current->sighand->siglock);
  57
  58 +       /* prevent accounting of that task to load */
  59 +       current->flags |= PF_FREEZING;
  60 +
  61         for (;;) {
  62                 set_current_state(TASK_UNINTERRUPTIBLE);
  63                 if (!frozen(current))
  64                         break;
  65                 schedule();
  66         }
  67 +
  68 +       /* Remove the accounting blocker */
  69 +       current->flags &= ~PF_FREEZING;
  70 +
  71         pr_debug("%s left refrigerator\n", current->comm);
  72         __set_current_state(save);
  73  }