Re: Deadlocks due to per-process plugging

From: Mike Galbraith
Date: Mon Jul 16 2012 - 06:08:37 EST


Hm, wonder how bad this sucks.. and if I should go hide under a big
sturdy rock after I poke xmit :)

---
block/blk-core.c | 1 +
kernel/rtmutex.c | 11 +++++++++--
2 files changed, 10 insertions(+), 2 deletions(-)

--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -2782,6 +2782,7 @@ void blk_flush_plug_list(struct blk_plug
if (q)
queue_unplugged(q, depth, from_schedule);
}
+EXPORT_SYMBOL(blk_flush_plug_list);

void blk_finish_plug(struct blk_plug *plug)
{
--- 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

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,
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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