__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 <[email protected]> --- 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
