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Date: Thu, 14 Feb 2019 17:12:36 +0100 From: Daniel Lezcano <daniel.lezcano@...aro.org> To: Thomas Gleixner <tglx@...utronix.de> Cc: Marc Zyngier <Marc.Zyngier@....com>, Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, "Rafael J. Wysocki" <rjw@...ysocki.net> Subject: Re: How to know if there is a pending interrupt when they are masked? Hi Thomas, On 14/02/2019 16:35, Thomas Gleixner wrote: > On Thu, 14 Feb 2019, Daniel Lezcano wrote: >> today we have the possibility to mask the local interrupt with the >> command local_irq_disable / local_irq_enable. >> >> The power management path disables the local interrupt in order to >> initiate a power down sequence. If there is a pending interrupt this one >> will make the power down function to abort, thus exiting right after >> calling the shutdown function after costly operations. It could be >> interesting to check if there is a pending interrupt before initiating >> the power down sequence. >> >> Is there a way to know if there is a pending interrupt on the current >> CPU when the local interrupt are disabled? Something like, >> local_irq_pending() function ? > > We have nothing like that today, but it would be possible to implement this > at least on x86 by peeking the local APIC registers. > > OTOH, the question is whether it's worth the trouble because the interrupt > could come in right after the query and the same issue which you want to > address persists. It only makes sense if it reduces the time window so > significantly that it actually matters. Yes, I agree. It should be worth only if we can prove we enter the deep idle sequence with pending interrupts much more often than what we expect. Actually, we have a similar action when the need_resched() is true, we abort the idle sequence and exit the loop. -- <http://www.linaro.org/> Linaro.org │ Open source software for ARM SoCs Follow Linaro: <http://www.facebook.com/pages/Linaro> Facebook | <http://twitter.com/#!/linaroorg> Twitter | <http://www.linaro.org/linaro-blog/> Blog
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