linux-kernel - Re: [PATCH 2/3] iommu/iova: don't disable preempt around this_cpu

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Message-ID: <20170628102625.GJ14532@8bytes.org>
Date:   Wed, 28 Jun 2017 12:26:25 +0200
From:   Joerg Roedel <joro@...tes.org>
To:     Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc:     tglx@...utronix.de, linux-kernel@...r.kernel.org,
        iommu@...ts.linux-foundation.org,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH 2/3] iommu/iova: don't disable preempt around
 this_cpu_ptr()

On Wed, Jun 28, 2017 at 11:31:55AM +0200, Sebastian Andrzej Siewior wrote:
> It really does. The spin_lock() does disable preemption but this is not
> the problem. The thing is that the preempt_disable() is superfluous and
> it hurts Preempt-RT (and this is how I noticed it). Also the
> get_cpu_ptr() is not requited and was only added to keep lockdep quiet
> (according to the history).
> Everything else here can stay as-is, I am just asking for the removal of
> the redundant preempt_disable() where it is not required.

Okay, makes sense, I applied both patches.


Thanks,

	Joerg