On Mon, 2012-07-16 at 12:19 +0200, Thomas Gleixner wrote:
> > @@ -647,8 +648,11 @@ static inline void rt_spin_lock_fastlock
> >
> > if (likely(rt_mutex_cmpxchg(lock, NULL, current)))
> > rt_mutex_deadlock_account_lock(lock, current);
> > - else
> > + else {
> > + if (blk_needs_flush_plug(current))
> > + blk_schedule_flush_plug(current);
> > slowfn(lock);
> > + }
>
> That should do the trick.
Box has been grinding away long enough now to agree that it did.
rt: pull your plug before blocking
Queued IO can lead to IO deadlock should a task require wakeup from as task
which is blocked on that queued IO.
ext3: dbench1 queues a buffer, blocks on journal mutex, it's plug is not
pulled. dbench2 mutex owner is waiting for kjournald, who is waiting for
the buffer queued by dbench1. Game over.
Signed-off-by: Mike Galbraith <efault@xxxxxx>
diff --git a/kernel/rtmutex.c b/kernel/rtmutex.c
index d58db99..39140a5 100644
--- a/kernel/rtmutex.c
+++ b/kernel/rtmutex.c
@@ -20,6 +20,7 @@
#include <linux/module.h>
#include <linux/sched.h>
#include <linux/timer.h>
+#include <linux/blkdev.h>
#include "rtmutex_common.h"
@@ -647,8 +648,11 @@ static inline void rt_spin_lock_fastlock(struct rt_mutex *lock,
if (likely(rt_mutex_cmpxchg(lock, NULL, current)))
rt_mutex_deadlock_account_lock(lock, current);
- else
+ else {
+ if (blk_needs_flush_plug(current))
+ blk_schedule_flush_plug(current);
slowfn(lock);
+ }
}
static inline void rt_spin_lock_fastunlock(struct rt_mutex *lock,
@@ -1104,8 +1108,11 @@ rt_mutex_fastlock(struct rt_mutex *lock, int state,
if (!detect_deadlock && likely(rt_mutex_cmpxchg(lock, NULL, current))) {
rt_mutex_deadlock_account_lock(lock, current);
return 0;
- } else
+ } else {
+ if (blk_needs_flush_plug(current))
+ blk_schedule_flush_plug(current);
return slowfn(lock, state, NULL, detect_deadlock);
+ }
}
static inline int
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