linux-kernel - Re: [v4.1.10-rt10][PATCH 1/2] genirq: introduce new generic_handle_irq_rt

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Message-ID: <563B8788.1090000@ti.com>
Date:	Thu, 5 Nov 2015 18:44:56 +0200
From:	Grygorii Strashko <grygorii.strashko@...com>
To:	Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
	Thomas Gleixner <tglx@...utronix.de>
CC:	<linux-rt-users@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	Sekhar Nori <nsekhar@...com>
Subject: Re: [v4.1.10-rt10][PATCH 1/2] genirq: introduce new
 generic_handle_irq_rt_wa() api

Hi Thomas, Sebastian,

On 11/03/2015 10:18 PM, Sebastian Andrzej Siewior wrote:
> On 11/03/2015 08:51 PM, Thomas Gleixner wrote:
>>> where MAX_MSI_IRQS = 32 now, but potentially can be increased up to 256.
>>
>> And you really oversimplified the code above. The reality is:
>>
>>      for (i = 0; i < MAX_MSI_CTRLS: i++) {
>>      	u32 status = read_msi_ctrl(i);
>>
>> 	for_each_bit(status)
>> 		handle_irq();
>>      }
>>
>> So sure, the worst case here is MAX_MSI_CTRLS * 32, but if all
>> possible 256 MSI interrupts are pending at the same time, you have
>> other problems than that.
>
> With threaded interrupts we would have 256 invocations of
> wake_up_process() so nothing should take ages.
>

Thanks a lot for your time and comments - I'll follow your
recommendations and use IRQF_NO_THREAD.

-- 
regards,
-grygorii
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