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authorJens Axboe <axboe@fb.com>2017-03-02 13:59:08 -0700
committerJens Axboe <axboe@fb.com>2017-03-02 13:59:08 -0700
commit7b36a7189fc320f0b783dd51bd1f541db56cfbdd (patch)
treec527bc3477255dfc0064390f2073533c6a652c2b
parenta5a79d00017c9eee68a9bcb40d5dfd6f45f17461 (diff)
block: don't call ioc_exit_icq() with the queue lock held for blk-mq
For legacy scheduling, we always call ioc_exit_icq() with both the ioc and queue lock held. This poses a problem for blk-mq with scheduling, since the queue lock isn't what we use in the scheduler. And since we don't need the queue lock held for ioc exit there, don't grab it and leave any extra locking up to the blk-mq scheduler. Reported-by: Paolo Valente <paolo.valente@linaro.org> Tested-by: Paolo Valente <paolo.valente@linaro.org> Reviewed-by: Omar Sandoval <osandov@fb.com> Signed-off-by: Jens Axboe <axboe@fb.com>
-rw-r--r--block/blk-ioc.c44
-rw-r--r--block/blk-sysfs.c2
-rw-r--r--block/elevator.c2
3 files changed, 31 insertions, 17 deletions
diff --git a/block/blk-ioc.c b/block/blk-ioc.c
index b12f9c87b4c3..0d7c96c0ba71 100644
--- a/block/blk-ioc.c
+++ b/block/blk-ioc.c
@@ -36,8 +36,8 @@ static void icq_free_icq_rcu(struct rcu_head *head)
}
/*
- * Exit an icq. Called with both ioc and q locked for sq, only ioc locked for
- * mq.
+ * Exit an icq. Called with ioc locked for blk-mq, and with both ioc
+ * and queue locked for legacy.
*/
static void ioc_exit_icq(struct io_cq *icq)
{
@@ -54,7 +54,10 @@ static void ioc_exit_icq(struct io_cq *icq)
icq->flags |= ICQ_EXITED;
}
-/* Release an icq. Called with both ioc and q locked. */
+/*
+ * Release an icq. Called with ioc locked for blk-mq, and with both ioc
+ * and queue locked for legacy.
+ */
static void ioc_destroy_icq(struct io_cq *icq)
{
struct io_context *ioc = icq->ioc;
@@ -62,7 +65,6 @@ static void ioc_destroy_icq(struct io_cq *icq)
struct elevator_type *et = q->elevator->type;
lockdep_assert_held(&ioc->lock);
- lockdep_assert_held(q->queue_lock);
radix_tree_delete(&ioc->icq_tree, icq->q->id);
hlist_del_init(&icq->ioc_node);
@@ -222,24 +224,40 @@ void exit_io_context(struct task_struct *task)
put_io_context_active(ioc);
}
+static void __ioc_clear_queue(struct list_head *icq_list)
+{
+ unsigned long flags;
+
+ while (!list_empty(icq_list)) {
+ struct io_cq *icq = list_entry(icq_list->next,
+ struct io_cq, q_node);
+ struct io_context *ioc = icq->ioc;
+
+ spin_lock_irqsave(&ioc->lock, flags);
+ ioc_destroy_icq(icq);
+ spin_unlock_irqrestore(&ioc->lock, flags);
+ }
+}
+
/**
* ioc_clear_queue - break any ioc association with the specified queue
* @q: request_queue being cleared
*
- * Walk @q->icq_list and exit all io_cq's. Must be called with @q locked.
+ * Walk @q->icq_list and exit all io_cq's.
*/
void ioc_clear_queue(struct request_queue *q)
{
- lockdep_assert_held(q->queue_lock);
+ LIST_HEAD(icq_list);
- while (!list_empty(&q->icq_list)) {
- struct io_cq *icq = list_entry(q->icq_list.next,
- struct io_cq, q_node);
- struct io_context *ioc = icq->ioc;
+ spin_lock_irq(q->queue_lock);
+ list_splice_init(&q->icq_list, &icq_list);
- spin_lock(&ioc->lock);
- ioc_destroy_icq(icq);
- spin_unlock(&ioc->lock);
+ if (q->mq_ops) {
+ spin_unlock_irq(q->queue_lock);
+ __ioc_clear_queue(&icq_list);
+ } else {
+ __ioc_clear_queue(&icq_list);
+ spin_unlock_irq(q->queue_lock);
}
}
diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
index 002af836aa87..c44b321335f3 100644
--- a/block/blk-sysfs.c
+++ b/block/blk-sysfs.c
@@ -815,9 +815,7 @@ static void blk_release_queue(struct kobject *kobj)
blkcg_exit_queue(q);
if (q->elevator) {
- spin_lock_irq(q->queue_lock);
ioc_clear_queue(q);
- spin_unlock_irq(q->queue_lock);
elevator_exit(q->elevator);
}
diff --git a/block/elevator.c b/block/elevator.c
index ac1c9f481a98..01139f549b5b 100644
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -983,9 +983,7 @@ static int elevator_switch(struct request_queue *q, struct elevator_type *new_e)
if (old_registered)
elv_unregister_queue(q);
- spin_lock_irq(q->queue_lock);
ioc_clear_queue(q);
- spin_unlock_irq(q->queue_lock);
}
/* allocate, init and register new elevator */