linux-kernel - Re: Long playing threaded interrupt handlers

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <alpine.LFD.2.00.1006020913310.2933@localhost.localdomain>
Date:	Wed, 2 Jun 2010 09:19:21 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Dmitry Torokhov <dmitry.torokhov@...il.com>
cc:	LKML <linux-kernel@...r.kernel.org>
Subject: Re: Long playing threaded interrupt handlers

On Wed, 2 Jun 2010, Dmitry Torokhov wrote:

> HI Thomas,
> 
> The threaded IRQ infrastructure that went into the kernel is extremely
> helpful, however in the input land there are quite a few devices that
> require polling after an IRQ has been raised.
> 
> Currently most such drivers, instead of threaded interrupts, still use
> [delayed] work to do the polling, and still face the issue of shutting
> down interrupt and scheduled work in a raceless way leaving irq enable
> counter balanced. Is it allowed to have threaded ISR execute for
> extended a amount of time, and do the required polling, provided that
> ISR does certain checks to finish promply in case when we unbind the
> driver or try to suspend the device?

Sure, why not ? The only thing we need to think about is when the poll
is busy polling for a long time, then we need to lower the irq thread
priority to SCHED_OTHER in order not to hog the CPU.

Vs. shutdown: The thread handler needs to be aware of a shutdown
request in it's poll loop, so something like this should work:

handler()
{
	while (work_to_do() && !shutdown) {
	      .....
	}
}

unbind()
{
	shutdown = 1;
	free_irq();
}

Thanks,

	tglx
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/