4.19-stable review patch. If anyone has any objections, please let me know.
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From: Zachary Hays zhays@lexmark.com
commit dcf6e2e38a1c7ccbc535de5e1d9b14998847499d upstream.
The kblockd workqueue is created with the WQ_MEM_RECLAIM flag set. This generates a rescuer thread for that queue that will trigger when the CPU is under heavy load and collect the uncompleted work.
In the case of mmc, this creates the possibility of a deadlock when there are multiple partitions on the device as other blk-mq work is also run on the same queue. For example:
- worker 0 claims the mmc host to work on partition 1 - worker 1 attempts to claim the host for partition 2 but has to wait for worker 0 to finish - worker 0 schedules complete_work to release the host - rescuer thread is triggered after time-out and collects the dangling work - rescuer thread attempts to complete the work in order starting with claim host - the task to release host is now blocked by a task to claim it and will never be called
The above results in multiple hung tasks that lead to failures to mount partitions.
Handling complete_work on a separate workqueue avoids this by keeping the work completion tasks separate from the other blk-mq work. This allows the host to be released without getting blocked by other tasks attempting to claim the host.
Signed-off-by: Zachary Hays zhays@lexmark.com Fixes: 81196976ed94 ("mmc: block: Add blk-mq support") Cc: stable@vger.kernel.org Signed-off-by: Ulf Hansson ulf.hansson@linaro.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- drivers/mmc/core/block.c | 10 +++++++++- include/linux/mmc/card.h | 1 + 2 files changed, 10 insertions(+), 1 deletion(-)
--- a/drivers/mmc/core/block.c +++ b/drivers/mmc/core/block.c @@ -2114,7 +2114,7 @@ static void mmc_blk_mq_req_done(struct m if (waiting) wake_up(&mq->wait); else - kblockd_schedule_work(&mq->complete_work); + queue_work(mq->card->complete_wq, &mq->complete_work);
return; } @@ -2928,6 +2928,13 @@ static int mmc_blk_probe(struct mmc_card
mmc_fixup_device(card, mmc_blk_fixups);
+ card->complete_wq = alloc_workqueue("mmc_complete", + WQ_MEM_RECLAIM | WQ_HIGHPRI, 0); + if (unlikely(!card->complete_wq)) { + pr_err("Failed to create mmc completion workqueue"); + return -ENOMEM; + } + md = mmc_blk_alloc(card); if (IS_ERR(md)) return PTR_ERR(md); @@ -2991,6 +2998,7 @@ static void mmc_blk_remove(struct mmc_ca pm_runtime_put_noidle(&card->dev); mmc_blk_remove_req(md); dev_set_drvdata(&card->dev, NULL); + destroy_workqueue(card->complete_wq); }
static int _mmc_blk_suspend(struct mmc_card *card) --- a/include/linux/mmc/card.h +++ b/include/linux/mmc/card.h @@ -308,6 +308,7 @@ struct mmc_card { unsigned int nr_parts;
unsigned int bouncesz; /* Bounce buffer size */ + struct workqueue_struct *complete_wq; /* Private workqueue */ };
static inline bool mmc_large_sector(struct mmc_card *card)