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>
This commit is contained in:
Thomas Gleixner 2012-12-20 18:28:26 +01:00 committed by Alibek Omarov
parent d124e035a9
commit b589f08bcb
1 changed files with 2 additions and 1 deletions

View File

@ -9,6 +9,7 @@
#include <linux/blkdev.h>
#include <linux/slab.h>
#include <linux/sched/task.h>
#include <linux/delay.h>
#include "blk.h"
@ -116,7 +117,7 @@ static void ioc_release_fn(struct work_struct *work)
spin_unlock(&q->queue_lock);
} else {
spin_unlock_irqrestore(&ioc->lock, flags);
cpu_relax();
cpu_chill();
spin_lock_irqsave_nested(&ioc->lock, flags, 1);
}
}