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Subject[PATCH RT] rtmutex: Flush block plug on __down_read()
Date
__down_read() bypasses the rtmutex frontend to call
rt_mutex_slowlock_locked() directly, and thus it needs to call
blk_schedule_flush_flug() itself.

Signed-off-by: Scott Wood <swood@redhat.com>
---
kernel/locking/rwsem-rt.c | 10 ++++++++++
1 file changed, 10 insertions(+)

diff --git a/kernel/locking/rwsem-rt.c b/kernel/locking/rwsem-rt.c
index 660e22caf709..f73cd4eda5cd 100644
--- a/kernel/locking/rwsem-rt.c
+++ b/kernel/locking/rwsem-rt.c
@@ -1,5 +1,6 @@
/*
*/
+#include <linux/blkdev.h>
#include <linux/rwsem.h>
#include <linux/sched/debug.h>
#include <linux/sched/signal.h>
@@ -88,6 +89,15 @@ static int __sched __down_read_common(struct rw_semaphore *sem, int state)
if (__down_read_trylock(sem))
return 0;

+ /*
+ * If sem->rtmutex blocks, the function sched_submit_work will not
+ * call blk_schedule_flush_plug (because tsk_is_pi_blocked would be
+ * true). We must call blk_schedule_flush_plug here; if we don't
+ * call it, an I/O deadlock may occur.
+ */
+ if (unlikely(blk_needs_flush_plug(current)))
+ blk_schedule_flush_plug(current);
+
might_sleep();
raw_spin_lock_irq(&m->wait_lock);
/*
--
1.8.3.1
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