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Date:   Fri, 27 Oct 2023 18:55:13 +0800
From:   Herbert Xu <herbert@gondor.apana.org.au>
To:     Giovanni Cabiddu <giovanni.cabiddu@intel.com>
Cc:     linux-crypto@vger.kernel.org, qat-linux@intel.com,
        Mikulas Patocka <mpatocka@redhat.com>
Subject: Re: [PATCH] crypto: qat - fix deadlock in backlog processing
Message-ID: <ZTuXERoS/ssVSth5@gondor.apana.org.au>
References: <20231020153330.70845-1-giovanni.cabiddu@intel.com>
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On Fri, Oct 20, 2023 at 04:33:21PM +0100, Giovanni Cabiddu wrote:
> If a request has the flag CRYPTO_TFM_REQ_MAY_BACKLOG set, the function
> qat_alg_send_message_maybacklog(), enqueues it in a backlog list if
> either (1) there is already at least one request in the backlog list, or
> (2) the HW ring is nearly full or (3) the enqueue to the HW ring fails.
> If an interrupt occurs right before the lock in qat_alg_backlog_req() is
> taken and the backlog queue is being emptied, then there is no request
> in the HW queues that can trigger a subsequent interrupt that can clear
> the backlog queue. In addition subsequent requests are enqueued to the
> backlog list and not sent to the hardware.
> 
> Fix it by holding the lock while taking the decision if the request
> needs to be included in the backlog queue or not. This synchronizes the
> flow with the interrupt handler that drains the backlog queue.
> 
> For performance reasons, the logic has been changed to try to enqueue
> first without holding the lock.
> 
> Fixes: 386823839732 ("crypto: qat - add backlog mechanism")
> Reported-by: Mikulas Patocka <mpatocka@redhat.com>
> Closes: https://lore.kernel.org/all/af9581e2-58f9-cc19-428f-6f18f1f83d54@redhat.com/T/
> Signed-off-by: Giovanni Cabiddu <giovanni.cabiddu@intel.com>
> ---
>  .../intel/qat/qat_common/qat_algs_send.c      | 46 ++++++++++---------
>  1 file changed, 25 insertions(+), 21 deletions(-)

Patch applied.  Thanks.
-- 
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
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