block, bfq: fix queue removal from weights tree
bfq maintains an ordered list, through a red-black tree, of unique weights of active bfq_queues. This list is used to detect whether there are active queues with differentiated weights. The weight of a queue is removed from the list when both the following two conditions become true: (1) the bfq_queue is flagged as inactive (2) the has no in-flight request any longer; Unfortunately, in the rare cases where condition (2) becomes true before condition (1), the removal fails, because the function to remove the weight of the queue (bfq_weights_tree_remove) is rightly invoked in the path that deactivates the bfq_queue, but mistakenly invoked *before* the function that actually performs the deactivation (bfq_deactivate_bfqq). This commits moves the invocation of bfq_weights_tree_remove for condition (1) to after bfq_deactivate_bfqq. As a consequence of this move, it is necessary to add a further reference to the queue when the weight of a queue is added, because the queue might otherwise be freed before bfq_weights_tree_remove is invoked. This commit adds this reference and makes all related modifications. Signed-off-by: Paolo Valente <paolo.valente@linaro.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
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d87447d84f
Коммит
9dee8b3b05
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@ -754,6 +754,7 @@ void bfq_weights_tree_add(struct bfq_data *bfqd, struct bfq_queue *bfqq,
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inc_counter:
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bfqq->weight_counter->num_active++;
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bfqq->ref++;
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}
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/*
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@ -778,6 +779,7 @@ void __bfq_weights_tree_remove(struct bfq_data *bfqd,
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reset_entity_pointer:
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bfqq->weight_counter = NULL;
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bfq_put_queue(bfqq);
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}
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/*
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@ -789,9 +791,6 @@ void bfq_weights_tree_remove(struct bfq_data *bfqd,
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{
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struct bfq_entity *entity = bfqq->entity.parent;
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__bfq_weights_tree_remove(bfqd, bfqq,
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&bfqd->queue_weights_tree);
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for_each_entity(entity) {
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struct bfq_sched_data *sd = entity->my_sched_data;
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@ -825,6 +824,15 @@ void bfq_weights_tree_remove(struct bfq_data *bfqd,
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bfqd->num_groups_with_pending_reqs--;
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}
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}
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/*
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* Next function is invoked last, because it causes bfqq to be
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* freed if the following holds: bfqq is not in service and
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* has no dispatched request. DO NOT use bfqq after the next
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* function invocation.
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*/
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__bfq_weights_tree_remove(bfqd, bfqq,
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&bfqd->queue_weights_tree);
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}
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/*
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@ -1020,7 +1028,8 @@ bfq_bfqq_resume_state(struct bfq_queue *bfqq, struct bfq_data *bfqd,
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static int bfqq_process_refs(struct bfq_queue *bfqq)
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{
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return bfqq->ref - bfqq->allocated - bfqq->entity.on_st;
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return bfqq->ref - bfqq->allocated - bfqq->entity.on_st -
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(bfqq->weight_counter != NULL);
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}
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/* Empty burst list and add just bfqq (see comments on bfq_handle_burst) */
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@ -1673,15 +1673,15 @@ void bfq_del_bfqq_busy(struct bfq_data *bfqd, struct bfq_queue *bfqq,
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bfqd->busy_queues[bfqq->ioprio_class - 1]--;
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if (!bfqq->dispatched)
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bfq_weights_tree_remove(bfqd, bfqq);
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if (bfqq->wr_coeff > 1)
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bfqd->wr_busy_queues--;
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bfqg_stats_update_dequeue(bfqq_group(bfqq));
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bfq_deactivate_bfqq(bfqd, bfqq, true, expiration);
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if (!bfqq->dispatched)
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bfq_weights_tree_remove(bfqd, bfqq);
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}
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/*
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