linux-kernel - Re: [Semaphore API] down_interruptible

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Message-ID: <55804408.2090507@free.fr>
Date:	Tue, 16 Jun 2015 17:43:04 +0200
From:	Mason <slash.tmp@...e.fr>
To:	Thomas Gleixner <tglx@...utronix.de>
CC:	LKML <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [Semaphore API] down_interruptible_timeout

On 15/06/2015 18:56, Thomas Gleixner wrote:

> On Mon, 15 Jun 2015, Mason wrote:
> 
>> A) process-context kernel thread fills a FIFO and calls down(&fifo_empty);
>> B) ISR handles the FIFO-empty interrupt with up(&fifo_empty);
>>
>> However, in case something goes wrong and the interrupt never fires,
>> I don't want the process to be stuck in an uninterruptible sleep.
>>
>> Perhaps I can set a tiny timeout (e.g. 10 µs) and not worry about
>> the interruptible part for such a small duration? (Hmm, __down_common
>> calls schedule_timeout, which is jiffies-based. I don't think there
>> is a hrtimers flavor. So µs timeouts would be off the table?)
>>
>> Or I could use the interruptible version, and let the user kill the
>> operation if necessary.
> 
> Use a completion.

Thanks for the pointer. I will also read the following LKML thread.
http://thread.gmane.org/gmane.linux.kernel/664514

Regards.

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