| Subject: block: Use cpu_chill() for retry loops |
| From: Thomas Gleixner <tglx@linutronix.de> |
| Date: Thu, 20 Dec 2012 18:28:26 +0100 |
| |
| 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. |
| |
| Signed-off-by: Thomas Gleixner <tglx@linutronix.de> |
| Cc: stable-rt@vger.kernel.org |
| --- |
| block/blk-ioc.c | 5 +++-- |
| 1 file changed, 3 insertions(+), 2 deletions(-) |
| |
| --- a/block/blk-ioc.c |
| +++ b/block/blk-ioc.c |
| @@ -8,6 +8,7 @@ |
| #include <linux/blkdev.h> |
| #include <linux/bootmem.h> /* for max_pfn/max_low_pfn */ |
| #include <linux/slab.h> |
| +#include <linux/delay.h> |
| |
| #include "blk.h" |
| |
| @@ -110,7 +111,7 @@ static void ioc_release_fn(struct work_s |
| spin_unlock(q->queue_lock); |
| } else { |
| spin_unlock_irqrestore(&ioc->lock, flags); |
| - cpu_relax(); |
| + cpu_chill(); |
| spin_lock_irqsave_nested(&ioc->lock, flags, 1); |
| } |
| } |
| @@ -188,7 +189,7 @@ retry: |
| spin_unlock(icq->q->queue_lock); |
| } else { |
| spin_unlock_irqrestore(&ioc->lock, flags); |
| - cpu_relax(); |
| + cpu_chill(); |
| goto retry; |
| } |
| } |