linux-kernel - Re: [PATCH] Lock 7 is cpuidle specific, use non-generic value for locking

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Message-ID: <20150313200204.GB16977@qualcomm.com>
Date:	Fri, 13 Mar 2015 15:02:04 -0500
From:	Andy Gross <agross@...eaurora.org>
To:	Lina Iyer <lina.iyer@...aro.org>
Cc:	Stephen Boyd <sboyd@...eaurora.org>,
	bjorn.andersson@...ymobile.com, linux-arm-msm@...r.kernel.org,
	jhugo@...eaurora.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Lock 7 is cpuidle specific, use non-generic value for
 locking

On Thu, Mar 12, 2015 at 04:16:00PM -0600, Lina Iyer wrote:

<snip>

> >It looks like the remote side unlocks it too? It doesn't seem like this
> >will work with the framework very well. The framework has a kernel
> >spinlock attached to the hwspinlock so when we lock the hwspinlock we
> >also lock the kernel spinlock and we only release the kernel spinlock
> >when the kernel unlocks the hwspinlock. In this case it seems like
> >cpuidle wants to have it's own kernel spinlock and just use the trylock
> >loop part of __hwspin_lock_timeout() without taking any kernel side
> >locks. Plus it wants to write a specific value to the lock.
> >
> Right.
> Just noticed that part of the hwspinlock. Yes SCM unlocks the
> hwspinlock. So I cannot hold any lock in Linux. May need changes in the
> hwspinlock framework. Seems like an additional flag in hwspinlock to not
> lock any in the trylock path work work. Hmm....

Or a specific EXPORT function for this one usecase which is unlike anyone elses
usage.

-- 
Qualcomm Innovation Center, Inc.
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project

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