First, it should be noted that the CQE timeout (60 seconds) is substantial so a CQE request that times out is really stuck, and the race between timeout and completion is extremely unlikely. Nevertheless this patch fixes an issue with it.

Commit ad73d6feadbd7b ("mmc: complete requests from ->timeout") preserved the existing functionality, to complete the request. However that had only been necessary because the block layer timeout handler had been marking the request to prevent it from being completed normally. That restriction was removed at the same time, the result being that a request that has gone will have been completed anyway. That is, the completion in the timeout handler became unnecessary.

At the time, the unnecessary completion was harmless because the block layer would ignore it, although that changed in kernel v5.0.

Note for stable, this patch will not apply cleanly without patch "mmc: core: Fix recursive locking issue in CQE recovery path"

Signed-off-by: Adrian Hunter adrian.hunter@intel.com Fixes: ad73d6feadbd7b ("mmc: complete requests from ->timeout") Cc: stable@vger.kernel.org ---

This is the patch I alluded to when replying to "mmc: core: Fix recursive locking issue in CQE recovery path"

drivers/mmc/core/queue.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/mmc/core/queue.c b/drivers/mmc/core/queue.c index 72bef39d7011..10ea67892b5f 100644 --- a/drivers/mmc/core/queue.c +++ b/drivers/mmc/core/queue.c @@ -110,8 +110,7 @@ static enum blk_eh_timer_return mmc_cqe_timed_out(struct request *req) mmc_cqe_recovery_notifier(mrq); return BLK_EH_RESET_TIMER; } - /* No timeout (XXX: huh? comment doesn't make much sense) */ - blk_mq_complete_request(req); + /* The request has gone already */ return BLK_EH_DONE; default: /* Timeout is handled by mmc core */

On Thu, 7 May 2020 at 18:15, Veerabhadrarao Badiganti vbadigan@codeaurora.org wrote:

From: Sarthak Garg sartgarg@codeaurora.org

Consider the following stack trace

-001|raw_spin_lock_irqsave -002|mmc_blk_cqe_complete_rq -003|__blk_mq_complete_request(inline) -003|blk_mq_complete_request(rq) -004|mmc_cqe_timed_out(inline) -004|mmc_mq_timed_out

mmc_mq_timed_out acquires the queue_lock for the first time. The mmc_blk_cqe_complete_rq function also tries to acquire the same queue lock resulting in recursive locking where the task is spinning for the same lock which it has already acquired leading to watchdog bark.

Fix this issue with the lock only for the required critical section.

Cc: stable@vger.kernel.org Fixes: 1e8e55b67030 ("mmc: block: Add CQE support") Suggested-by: Sahitya Tummala stummala@codeaurora.org Signed-off-by: Sarthak Garg sartgarg@codeaurora.org

Applied for fixes, thanks!

Kind regards Uffe

---

drivers/mmc/core/queue.c | 13 ++++--------- 1 file changed, 4 insertions(+), 9 deletions(-)

diff --git a/drivers/mmc/core/queue.c b/drivers/mmc/core/queue.c index 25bee3d..b5fd3bc 100644 --- a/drivers/mmc/core/queue.c +++ b/drivers/mmc/core/queue.c @@ -107,7 +107,7 @@ static enum blk_eh_timer_return mmc_cqe_timed_out(struct request *req) case MMC_ISSUE_DCMD: if (host->cqe_ops->cqe_timeout(host, mrq, &recovery_needed)) { if (recovery_needed)

•                           __mmc_cqe_recovery_notifier(mq);
  

•                           mmc_cqe_recovery_notifier(mrq);
                    return BLK_EH_RESET_TIMER;
            }
            /* No timeout (XXX: huh? comment doesn't make much sense) */
  

@@ -127,18 +127,13 @@ static enum blk_eh_timer_return mmc_mq_timed_out(struct request *req, struct mmc_card *card = mq->card; struct mmc_host *host = card->host; unsigned long flags;

•   int ret;
  

•   bool ignore_tout;
  
    spin_lock_irqsave(&mq->lock, flags);
  

•   if (mq->recovery_needed || !mq->use_cqe || host->hsq_enabled)
  

•           ret = BLK_EH_RESET_TIMER;
  

•   else
  

•           ret = mmc_cqe_timed_out(req);
  

•   ignore_tout = mq->recovery_needed || !mq->use_cqe || host->hsq_enabled;
    spin_unlock_irqrestore(&mq->lock, flags);
  
  

•   return ret;
  

•   return ignore_tout ? BLK_EH_RESET_TIMER : mmc_cqe_timed_out(req);
  

}

static void mmc_mq_recovery_handler(struct work_struct *work)

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