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authorPaolo Valente <paolo.valente@linaro.org>2019-01-29 14:06:34 +0300
committerJens Axboe <axboe@kernel.dk>2019-01-31 22:50:24 +0300
commit9dee8b3b057e1da26f85f1842f2aaf3bb200fb94 (patch)
tree909db0541b6ce1e5368ea986cde0483cdeddd32f /block/bfq-iosched.c
parentd87447d84fe194b0e4f5413b5344dc82cc100711 (diff)
downloadlinux-9dee8b3b057e1da26f85f1842f2aaf3bb200fb94.tar.xz
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>
Diffstat (limited to 'block/bfq-iosched.c')
-rw-r--r--block/bfq-iosched.c17
1 files changed, 13 insertions, 4 deletions
diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c
index 12228af16198..bf585ad29bb5 100644
--- a/block/bfq-iosched.c
+++ b/block/bfq-iosched.c
@@ -754,6 +754,7 @@ void bfq_weights_tree_add(struct bfq_data *bfqd, struct bfq_queue *bfqq,
inc_counter:
bfqq->weight_counter->num_active++;
+ bfqq->ref++;
}
/*
@@ -778,6 +779,7 @@ void __bfq_weights_tree_remove(struct bfq_data *bfqd,
reset_entity_pointer:
bfqq->weight_counter = NULL;
+ bfq_put_queue(bfqq);
}
/*
@@ -789,9 +791,6 @@ void bfq_weights_tree_remove(struct bfq_data *bfqd,
{
struct bfq_entity *entity = bfqq->entity.parent;
- __bfq_weights_tree_remove(bfqd, bfqq,
- &bfqd->queue_weights_tree);
-
for_each_entity(entity) {
struct bfq_sched_data *sd = entity->my_sched_data;
@@ -825,6 +824,15 @@ void bfq_weights_tree_remove(struct bfq_data *bfqd,
bfqd->num_groups_with_pending_reqs--;
}
}
+
+ /*
+ * Next function is invoked last, because it causes bfqq to be
+ * freed if the following holds: bfqq is not in service and
+ * has no dispatched request. DO NOT use bfqq after the next
+ * function invocation.
+ */
+ __bfq_weights_tree_remove(bfqd, bfqq,
+ &bfqd->queue_weights_tree);
}
/*
@@ -1020,7 +1028,8 @@ bfq_bfqq_resume_state(struct bfq_queue *bfqq, struct bfq_data *bfqd,
static int bfqq_process_refs(struct bfq_queue *bfqq)
{
- return bfqq->ref - bfqq->allocated - bfqq->entity.on_st;
+ return bfqq->ref - bfqq->allocated - bfqq->entity.on_st -
+ (bfqq->weight_counter != NULL);
}
/* Empty burst list and add just bfqq (see comments on bfq_handle_burst) */