block: Use cpu_chill() for retry loops
Retry loops on RT might loop forever when the modifying side was preempted. Steven also observed a live lock when there was a concurrent priority boosting going on. Use cpu_chill() instead of cpu_relax() to let the system make progress. [bigeasy: After all those changes that occured over the years, this one hunk is left and should not cause any starvation on -RT anymore] Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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@ -9,6 +9,7 @@
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#include <linux/blkdev.h>
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#include <linux/blkdev.h>
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#include <linux/slab.h>
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#include <linux/slab.h>
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#include <linux/sched/task.h>
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#include <linux/sched/task.h>
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#include <linux/delay.h>
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#include "blk.h"
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#include "blk.h"
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@ -116,7 +117,7 @@ static void ioc_release_fn(struct work_struct *work)
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spin_unlock(&q->queue_lock);
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spin_unlock(&q->queue_lock);
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} else {
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} else {
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spin_unlock_irqrestore(&ioc->lock, flags);
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spin_unlock_irqrestore(&ioc->lock, flags);
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cpu_relax();
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cpu_chill();
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spin_lock_irqsave_nested(&ioc->lock, flags, 1);
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spin_lock_irqsave_nested(&ioc->lock, flags, 1);
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}
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}
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}
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}
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