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Commit 02acc80d authored by Sebastian Andrzej Siewior's avatar Sebastian Andrzej Siewior Committed by Thomas Gleixner
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delayacct: Use raw_spinlocks 



try_to_wake_up() might invoke delayacct_blkio_end() while holding the
pi_lock (which is a raw_spinlock_t). delayacct_blkio_end() acquires
task_delay_info.lock which is a spinlock_t. This causes a might sleep splat
on -RT where non raw spinlocks are converted to 'sleeping' spinlocks.

task_delay_info.lock is only held for a short amount of time so it's not a
problem latency wise to make convert it to a raw spinlock.

Signed-off-by: default avatarSebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Cc: Balbir Singh <bsingharora@gmail.com>
Link: https://lkml.kernel.org/r/20180423161024.6710-1-bigeasy@linutronix.de
parent 3bea9adc

include/linux/delayacct.h

+1 −1
Original line number Diff line number Diff line
@@ -29,7 +29,7 @@ 


#ifdef CONFIG_TASK_DELAY_ACCT

struct task_delay_info {

	spinlock_t	lock;

	raw_spinlock_t	lock;

	unsigned int	flags;	/* Private per-task flags */



	/* For each stat XXX, add following, aligned appropriately

kernel/delayacct.c

+9 −8
Original line number Diff line number Diff line
@@ -44,23 +44,24 @@ void __delayacct_tsk_init(struct task_struct *tsk) 
{

	tsk->delays = kmem_cache_zalloc(delayacct_cache, GFP_KERNEL);

	if (tsk->delays)

		spin_lock_init(&tsk->delays->lock);

		raw_spin_lock_init(&tsk->delays->lock);

}



/*

 * Finish delay accounting for a statistic using its timestamps (@start),

 * accumalator (@total) and @count

 */

static void delayacct_end(spinlock_t *lock, u64 *start, u64 *total, u32 *count)

static void delayacct_end(raw_spinlock_t *lock, u64 *start, u64 *total,

			  u32 *count)

{

	s64 ns = ktime_get_ns() - *start;

	unsigned long flags;



	if (ns > 0) {

		spin_lock_irqsave(lock, flags);

		raw_spin_lock_irqsave(lock, flags);

		*total += ns;

		(*count)++;

		spin_unlock_irqrestore(lock, flags);

		raw_spin_unlock_irqrestore(lock, flags);

	}

}
@@ -127,7 +128,7 @@ int __delayacct_add_tsk(struct taskstats *d, struct task_struct *tsk) 


	/* zero XXX_total, non-zero XXX_count implies XXX stat overflowed */



	spin_lock_irqsave(&tsk->delays->lock, flags);

	raw_spin_lock_irqsave(&tsk->delays->lock, flags);

	tmp = d->blkio_delay_total + tsk->delays->blkio_delay;

	d->blkio_delay_total = (tmp < d->blkio_delay_total) ? 0 : tmp;

	tmp = d->swapin_delay_total + tsk->delays->swapin_delay;
@@ -137,7 +138,7 @@ int __delayacct_add_tsk(struct taskstats *d, struct task_struct *tsk) 
	d->blkio_count += tsk->delays->blkio_count;

	d->swapin_count += tsk->delays->swapin_count;

	d->freepages_count += tsk->delays->freepages_count;

	spin_unlock_irqrestore(&tsk->delays->lock, flags);

	raw_spin_unlock_irqrestore(&tsk->delays->lock, flags);



	return 0;

}
@@ -147,10 +148,10 @@ __u64 __delayacct_blkio_ticks(struct task_struct *tsk) 
	__u64 ret;

	unsigned long flags;



	spin_lock_irqsave(&tsk->delays->lock, flags);

	raw_spin_lock_irqsave(&tsk->delays->lock, flags);

	ret = nsec_to_clock_t(tsk->delays->blkio_delay +

				tsk->delays->swapin_delay);

	spin_unlock_irqrestore(&tsk->delays->lock, flags);

	raw_spin_unlock_irqrestore(&tsk->delays->lock, flags);

	return ret;

}