From: lars@metafoo•de (Lars-Peter Clausen)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH v3] iio: adc: xilinx-xadc: Push interrupts into threaded context
Date: Tue, 04 Aug 2015 10:05:00 +0200 [thread overview]
Message-ID: <55C0722C.7080904@metafoo.de> (raw)
In-Reply-To: <CAKfKVtGegy2P_YWQAtKEzByN-+q+bq=uus4zNvO4sghXRjpGPQ@mail.gmail.com>
On 08/04/2015 07:34 AM, Shubhrajyoti Datta wrote:
> On Fri, Jul 24, 2015 at 6:08 PM, Lars-Peter Clausen <lars@metafoo•de> wrote:
>> Hi,
>>
>> Sorry, but I don't think this patch has been sufficiently tested against a
>> mainline kernel. The driver wont even probe the way it is right now.
>>
>> On 07/21/2015 01:14 AM, Xander Huff wrote:
>>>
>>> The driver currently registers a pair of irq handlers using
>>> request_threaded_irq(), however the synchronization mechanism between the
>>> hardirq and the threadedirq handler is a regular spinlock.
>>
>>
>> If everything runs in threaded context we don't really need the spinlock
>> anymore and can use the mutex throughout.
>
> that should be better from the performance point of view.
>
>>
>>>
>>> Unfortunately, this breaks PREEMPT_RT builds, where a spinlock can sleep,
>>> and is thus not able to be acquired from a hardirq handler. This patch
>>> gets
>>> rid of the hardirq handler and pushes all interrupt handling into the
>>> threaded context.
>>
>>
>> We actually might as well run everything in the hardirq handler (which will
>> be threaded in PREEMPT_RT). The reason why we have the threaded handler is
>> because xadc_handle_event() used to sleep, but it doesn't do this anymore.
>
> The point is why have the hard irq. If we use hardirq then not mutex
> can be used and spinlock will
> be busy.
Well there is no need to use a threaded IRQ. The interrupt handler is quite
small and doesn't take too much time and doesn't have any delays or sleeps
in it either.
next prev parent reply other threads:[~2015-08-04 8:05 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-05-07 15:38 [PATCH] iio: adc: xilinx-xadc: Convert to raw spinlock Xander Huff
2015-05-14 17:10 ` Sebastian Andrzej Siewior
2015-05-14 22:45 ` Xander Huff
2015-05-18 21:17 ` Sebastian Andrzej Siewior
2015-05-23 11:36 ` Jonathan Cameron
2015-06-07 15:29 ` Jonathan Cameron
2015-06-08 14:44 ` Xander Huff
2015-07-08 21:38 ` [PATCH v2] iio: adc: xilinx-xadc: Push interrupts into threaded context Xander Huff
2015-07-14 14:28 ` Sebastian Andrzej Siewior
2015-07-15 15:59 ` Xander Huff
[not found] ` <CAKfKVtGTO81wLWk50M303t2WjcBEMEt_LUnsJ3_WmvR_3izUjg@mail.gmail.com>
2015-07-15 15:57 ` Xander Huff
2015-07-20 23:14 ` [PATCH v3] " Xander Huff
2015-07-24 12:38 ` Lars-Peter Clausen
2015-08-03 20:18 ` Xander Huff
2015-08-04 8:01 ` Lars-Peter Clausen
2015-08-11 23:00 ` [PATCH v4] iio: adc: xilinx-xadc: Push interrupts into hardirq context Xander Huff
2015-08-12 15:17 ` Lars-Peter Clausen
2015-08-12 16:33 ` Sebastian Andrzej Siewior
2015-08-15 19:55 ` Jonathan Cameron
2015-08-04 5:34 ` [PATCH v3] iio: adc: xilinx-xadc: Push interrupts into threaded context Shubhrajyoti Datta
2015-08-04 8:05 ` Lars-Peter Clausen [this message]
2015-08-07 3:55 ` Shubhrajyoti Datta
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