releases/4.14.60/delayacct-use-raw_spinlocks.patch

   1 From foo@baz Sat Jul 28 10:25:26 CEST 2018
   2 From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
   3 Date: Mon, 23 Apr 2018 18:10:23 +0200
   4 Subject: delayacct: Use raw_spinlocks
   5
   6 From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
   7
   8 [ Upstream commit 02acc80d19edb0d5684c997b2004ad19f9f5236e ]
   9
  10 try_to_wake_up() might invoke delayacct_blkio_end() while holding the
  11 pi_lock (which is a raw_spinlock_t). delayacct_blkio_end() acquires
  12 task_delay_info.lock which is a spinlock_t. This causes a might sleep splat
  13 on -RT where non raw spinlocks are converted to 'sleeping' spinlocks.
  14
  15 task_delay_info.lock is only held for a short amount of time so it's not a
  16 problem latency wise to make convert it to a raw spinlock.
  17
  18 Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
  19 Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
  20 Cc: Balbir Singh <bsingharora@gmail.com>
  21 Link: https://lkml.kernel.org/r/20180423161024.6710-1-bigeasy@linutronix.de
  22 Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
  23 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  24 ---
  25  include/linux/delayacct.h |    2 +-
  26  kernel/delayacct.c        |   17 +++++++++--------
  27  2 files changed, 10 insertions(+), 9 deletions(-)
  28
  29 --- a/include/linux/delayacct.h
  30 +++ b/include/linux/delayacct.h
  31 @@ -29,7 +29,7 @@
  32
  33  #ifdef CONFIG_TASK_DELAY_ACCT
  34  struct task_delay_info {
  35 -       spinlock_t      lock;
  36 +       raw_spinlock_t  lock;
  37         unsigned int    flags;  /* Private per-task flags */
  38
  39         /* For each stat XXX, add following, aligned appropriately
  40 --- a/kernel/delayacct.c
  41 +++ b/kernel/delayacct.c
  42 @@ -44,23 +44,24 @@ void __delayacct_tsk_init(struct task_st
  43  {
  44         tsk->delays = kmem_cache_zalloc(delayacct_cache, GFP_KERNEL);
  45         if (tsk->delays)
  46 -               spin_lock_init(&tsk->delays->lock);
  47 +               raw_spin_lock_init(&tsk->delays->lock);
  48  }
  49
  50  /*
  51   * Finish delay accounting for a statistic using its timestamps (@start),
  52   * accumalator (@total) and @count
  53   */
  54 -static void delayacct_end(spinlock_t *lock, u64 *start, u64 *total, u32 *count)
  55 +static void delayacct_end(raw_spinlock_t *lock, u64 *start, u64 *total,
  56 +                         u32 *count)
  57  {
  58         s64 ns = ktime_get_ns() - *start;
  59         unsigned long flags;
  60
  61         if (ns > 0) {
  62 -               spin_lock_irqsave(lock, flags);
  63 +               raw_spin_lock_irqsave(lock, flags);
  64                 *total += ns;
  65                 (*count)++;
  66 -               spin_unlock_irqrestore(lock, flags);
  67 +               raw_spin_unlock_irqrestore(lock, flags);
  68         }
  69  }
  70
  71 @@ -127,7 +128,7 @@ int __delayacct_add_tsk(struct taskstats
  72
  73         /* zero XXX_total, non-zero XXX_count implies XXX stat overflowed */
  74
  75 -       spin_lock_irqsave(&tsk->delays->lock, flags);
  76 +       raw_spin_lock_irqsave(&tsk->delays->lock, flags);
  77         tmp = d->blkio_delay_total + tsk->delays->blkio_delay;
  78         d->blkio_delay_total = (tmp < d->blkio_delay_total) ? 0 : tmp;
  79         tmp = d->swapin_delay_total + tsk->delays->swapin_delay;
  80 @@ -137,7 +138,7 @@ int __delayacct_add_tsk(struct taskstats
  81         d->blkio_count += tsk->delays->blkio_count;
  82         d->swapin_count += tsk->delays->swapin_count;
  83         d->freepages_count += tsk->delays->freepages_count;
  84 -       spin_unlock_irqrestore(&tsk->delays->lock, flags);
  85 +       raw_spin_unlock_irqrestore(&tsk->delays->lock, flags);
  86
  87         return 0;
  88  }
  89 @@ -147,10 +148,10 @@ __u64 __delayacct_blkio_ticks(struct tas
  90         __u64 ret;
  91         unsigned long flags;
  92
  93 -       spin_lock_irqsave(&tsk->delays->lock, flags);
  94 +       raw_spin_lock_irqsave(&tsk->delays->lock, flags);
  95         ret = nsec_to_clock_t(tsk->delays->blkio_delay +
  96                                 tsk->delays->swapin_delay);
  97 -       spin_unlock_irqrestore(&tsk->delays->lock, flags);
  98 +       raw_spin_unlock_irqrestore(&tsk->delays->lock, flags);
  99         return ret;
 100  }
 101