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FAILED: patch "[PATCH] mmc: core: Fix recursive locking issue in CQE recovery path" failed to apply to 4.19-stable tree

PATCH [email protected] 1 participant 1 message May 18, 2020

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The patch below does not apply to the 4.19-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 39a22f73744d5baee30b5f134ae2e30b668b66ed Mon Sep 17 00:00:00 2001
From: Sarthak Garg <[email protected]>
Date: Thu, 7 May 2020 21:45:33 +0530
Subject: [PATCH] mmc: core: Fix recursive locking issue in CQE recovery path

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 <[email protected]>
Fixes 1e8e55b67030 ("mmc: block: Add CQE support")
Suggested-by Sahitya Tummala <[email protected]>
Signed-off-by Sarthak Garg <[email protected]>
Acked-by Adrian Hunter <[email protected]>
Link https://lore.kernel.org/r/[email protected] open here
Signed-off-by Ulf Hansson <[email protected]>
drivers/mmc/core/queue.c +4 -9
index 25bee3daf9e2..b5fd3bc7eb58 100644
@@ -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)