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Re: [PATCH] null_blk: don't enable irqs when in irq

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On 12/25/2015 09:03 PM, Jens Axboe wrote:
> On 12/25/2015 07:26 AM, Rabin Vincent wrote:
>> When using irq_mode=NULL_IRQ_TIMER, blk_start_queue() is called from the
>> hrtimer interrupt.  null_request_fn() calls spin_unlock_irq() and this
>> causes the following splat from lockdep since interrupts are being
>> enabled while we're in an interrupt handler.
>>
>> When we're in null_request_fn() we can't know the status of the flags
>> saved before blk_start_queue() was called, but we can use in_irq() to
>> conditionally enable interrupts only if we're not in a hard interrupt in
>> order to handle this case.
>
> Using in_irq() to check for this is... nasty. You have two choices here.
> Either you don't enable interrupts ever. That's safe from the
> perspective of the driver, since we don't block in handling the command.
> That means just unconditionally using spin_unlock() in the request_fn.
> Or you punt queue running to process context, by manually clearing the
> queue stopped flag and using blk_run_queue_async() instead.

Something like this should work, can you test it?


-- 
Jens Axboe

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[PATCH] null_blk: don't enable irqs when in irq Rabin Vincent <rabin@rab.in> - 2015-12-25 15:30 +0100
  Re: [PATCH] null_blk: don't enable irqs when in irq Jens Axboe <axboe@fb.com> - 2015-12-26 05:10 +0100
    Re: [PATCH] null_blk: don't enable irqs when in irq Jens Axboe <axboe@fb.com> - 2015-12-28 20:00 +0100
      Re: [PATCH] null_blk: don't enable irqs when in irq Rabin Vincent <rabin@rab.in> - 2015-12-28 20:10 +0100
        Re: [PATCH] null_blk: don't enable irqs when in irq Jens Axboe <axboe@fb.com> - 2015-12-28 20:20 +0100
          Re: [PATCH] null_blk: don't enable irqs when in irq Rabin Vincent <rabin@rab.in> - 2015-12-28 21:00 +0100
            Re: [PATCH] null_blk: don't enable irqs when in irq Jens Axboe <axboe@fb.com> - 2015-12-28 21:20 +0100

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