From: Thomas Gleixner Date: Thu, 20 Dec 2012 18:28:26 +0100 Subject: [PATCH 187/290] block: Use cpu_chill() for retry loops Origin: https://git.kernel.org/cgit/linux/kernel/git/rt/linux-stable-rt.git/commit?id=9cf22ca96dd1665b30609658a308c09ecb55c1c1 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 --- 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 01580f88fcb3..98d87e52ccdc 100644 --- a/block/blk-ioc.c +++ b/block/blk-ioc.c @@ -9,6 +9,7 @@ #include #include #include +#include #include "blk.h" @@ -118,7 +119,7 @@ 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); } } @@ -202,7 +203,7 @@ 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; } }