blk-mq-sched: don't hold queue_lock when calling exit_icq
None of the other blk-mq elevator hooks are called with this lock held. Additionally, it can lead to circular locking dependencies between queue_lock and the private scheduler lock. Reported-by: Paolo Valente <paolo.valente@linaro.org> Signed-off-by: Omar Sandoval <osandov@fb.com> Signed-off-by: Jens Axboe <axboe@fb.com>
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@ -35,7 +35,10 @@ static void icq_free_icq_rcu(struct rcu_head *head)
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kmem_cache_free(icq->__rcu_icq_cache, icq);
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}
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/* Exit an icq. Called with both ioc and q locked. */
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/*
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* Exit an icq. Called with both ioc and q locked for sq, only ioc locked for
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* mq.
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*/
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static void ioc_exit_icq(struct io_cq *icq)
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{
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struct elevator_type *et = icq->q->elevator->type;
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@ -166,6 +169,7 @@ EXPORT_SYMBOL(put_io_context);
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*/
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void put_io_context_active(struct io_context *ioc)
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{
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struct elevator_type *et;
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unsigned long flags;
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struct io_cq *icq;
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@ -184,13 +188,19 @@ retry:
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hlist_for_each_entry(icq, &ioc->icq_list, ioc_node) {
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if (icq->flags & ICQ_EXITED)
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continue;
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if (spin_trylock(icq->q->queue_lock)) {
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et = icq->q->elevator->type;
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if (et->uses_mq) {
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ioc_exit_icq(icq);
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spin_unlock(icq->q->queue_lock);
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} else {
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spin_unlock_irqrestore(&ioc->lock, flags);
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cpu_relax();
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goto retry;
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if (spin_trylock(icq->q->queue_lock)) {
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ioc_exit_icq(icq);
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spin_unlock(icq->q->queue_lock);
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} else {
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spin_unlock_irqrestore(&ioc->lock, flags);
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cpu_relax();
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goto retry;
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}
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}
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}
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spin_unlock_irqrestore(&ioc->lock, flags);
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