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From: Thomas Gleixner <tglx@linutronix.de>
Date: Thu, 20 Dec 2012 18:28:26 +0100
Subject: [PATCH 186/353] block: Use cpu_chill() for retry loops
Origin: https://git.kernel.org/cgit/linux/kernel/git/rt/linux-stable-rt.git/commit?id=51606351531762f808faee325d6318f493efbd6f
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>
---
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 4c810969c3e2..48089f5bcc11 100644
--- a/block/blk-ioc.c
+++ b/block/blk-ioc.c
@@ -9,6 +9,7 @@
#include <linux/blkdev.h>
#include <linux/slab.h>
#include <linux/sched/task.h>
+#include <linux/delay.h>
#include "blk.h"
@@ -119,7 +120,7 @@ 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);
}
}
@@ -203,7 +204,7 @@ void put_io_context_active(struct io_context *ioc)
spin_unlock(icq->q->queue_lock);
} else {
spin_unlock_irqrestore(&ioc->lock, flags);
- cpu_relax();
+ cpu_chill();
goto retry;
}
}
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