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	Wed, 25 May 2016 15:16:18 -0400
Subject: Re: [PATCH 2/5] block: add queue reset support
To: Bart Van Assche <bart.vanassche@sandisk.com>,
	linux-scsi@vger.kernel.org, linux-block@vger.kernel.org,
	target-devel@vger.kernel.org
References: <1464162903-14735-1-git-send-email-mchristi@redhat.com>
 <1464162903-14735-3-git-send-email-mchristi@redhat.com>
 <f30ef794-b7ed-36d3-a268-b3bd6249ae50@sandisk.com>
From: Mike Christie <mchristi@redhat.com>
Message-ID: <5745F9FF.7070101@redhat.com>
Date: Wed, 25 May 2016 14:16:15 -0500
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On 05/25/2016 11:13 AM, Bart Van Assche wrote:
> On 05/25/2016 12:55 AM, mchristi@redhat.com wrote:
>> +    spin_lock_irq(q->queue_lock);
>> +    wait_event_lock_irq(q->reset_wq,
>> +                !queue_flag_test_and_set(QUEUE_FLAG_RESETTING, q),
>> +                *q->queue_lock);
>> +    if (blk_queue_dead(q)) {
>> +        rc = -ENODEV;
>> +        spin_unlock_irq(q->queue_lock);
>> +        goto done;
>> +    }
>> +    spin_unlock_irq(q->queue_lock);
> 
> Is the flag QUEUE_FLAG_RESETTING used to serialize blk_reset_queue()
> calls? If so, please consider using a mutex instead. Lockdep can detect
> lock inversion for mutexes and spinlocks but not for serialization that
> is based on wait_event_lock_irq() loops.

Will do.

> 
>> +    if (q->mq_ops) {
>> +        blk_mq_stop_hw_queues(q);
>> +        blk_mq_freeze_queue(q);
>> +
>> +        eh_rc = q->mq_ops->reset(q);
>> +
>> +        blk_mq_unfreeze_queue(q);
>> +        blk_mq_start_stopped_hw_queues(q, true);
>> +    } else if (q->reset_fn) {
>> +        spin_lock_irq(q->queue_lock);
>> +        blk_stop_queue(q);
>> +        spin_unlock_irq(q->queue_lock);
>> +
>> +        while (q->request_fn_active)
>> +            msleep(10);
>> +
>> +        eh_rc = q->reset_fn(q);
>> +
>> +        spin_lock_irq(q->queue_lock);
>> +        blk_start_queue(q);
>> +        spin_unlock_irq(q->queue_lock);
>> +    }
> 
> Some of the above code is similar to some of the code in
> scsi_internal_device_block() and scsi_internal_device_unblock(). Have
> you considered to avoid this duplication by introducing helpers in the
> block layer for blocking and unblocking queues?
> 

Will do. Thanks.