linux-kernel - Re: [4.19.124 V1] mmc: core: Fix recursive locking issue in CQE recovery path

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Date:   Mon, 1 Jun 2020 13:11:05 +0200
From:   Greg KH <greg@...ah.com>
To:     Sarthak Garg <sartgarg@...eaurora.org>
Cc:     stable@...r.kernel.org, adrian.hunter@...el.com,
        ulf.hansson@...aro.org, vbadigan@...eaurora.org,
        stummala@...eaurora.org, linux-mmc@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org
Subject: Re: [4.19.124 V1] mmc: core: Fix recursive locking issue in CQE
 recovery path

On Wed, May 27, 2020 at 05:49:02PM +0530, Sarthak Garg wrote:
> [ Upstream commit 39a22f73744d5baee30b5f134ae2e30b668b66ed ]
> 
> 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@...r.kernel.org>
> Fixes: 1e8e55b67030 ("mmc: block: Add CQE support")
> Suggested-by: Sahitya Tummala <stummala@...eaurora.org>
> Signed-off-by: Sarthak Garg <sartgarg@...eaurora.org>
> Acked-by: Adrian Hunter <adrian.hunter@...el.com>
> Link: https://lore.kernel.org/r/1588868135-31783-1-git-send-email-vbadigan@codeaurora.org
> Signed-off-by: Ulf Hansson <ulf.hansson@...aro.org>
> ---

Thanks for the backport, now queued up.

greg k-h