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From: Thomas Gleixner <tglx@linutronix.de>
To: Valentin Schneider <valentin.schneider@arm.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will@kernel.org>,
	LKML <linux-kernel@vger.kernel.org>,
	LAK <linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH] arm64: Avoid pointless schedule_preempt_irq() invocations
Date: Wed, 17 Jul 2019 12:04:55 +0200 (CEST)
Message-ID: <alpine.DEB.2.21.1907171203280.1767@nanos.tec.linutronix.de> (raw)
In-Reply-To: <e47e8298-af21-64fa-eac3-6fdfbf11c502@arm.com>

On Wed, 17 Jul 2019, Valentin Schneider wrote:

> On 17/07/2019 09:43, Thomas Gleixner wrote:
> > When preempt_count is zero on return from interrupt then
> > schedule_preempt_irq() is invoked even if TIF_NEED_RESCHED is not set.
> > 
> > That does not make sense because schedule_preempt_irq() has to go through a
> > full __schedule() for nothing in that case.
> > 
> > Check TIF_NEED_RESCHED and invoke schedule_preempt_irq() only if set.
> > 
> > Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
> 
> Don't we have NEED_RESCHED squashed into preempt count?
> 
>   396244692232 ("arm64: preempt: Provide our own implementation of asm/preempt.h")
> 
> So the existing check should cover that, unless I'm missing something?

Right. Ignore me.

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Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-07-17  8:43 Thomas Gleixner
2019-07-17  9:54 ` Valentin Schneider
2019-07-17 10:04   ` Thomas Gleixner [this message]

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