From: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
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@xxxxxxxxxxxxx>
Cc: stable-rt@xxxxxxxxxxxxxxx
---
block/blk-ioc.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/block/blk-ioc.c b/block/blk-ioc.c
index fb95dd2..6b54201 100644
--- 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_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);
}
}
@@ -188,7 +189,7 @@ retry:
spin_unlock(icq->q->queue_lock);
} else {
spin_unlock_irqrestore(&ioc->lock, flags);
- cpu_relax();
+ cpu_chill();
goto retry;
}
}
--
1.7.10.4
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