linux-kernel - Re: [PATCH 00/10 v2] iommu/amd: lock splitting & GFP

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Message-ID: <20180319121527.zdmuwid4i3mjpwjw@linutronix.de>
Date:   Mon, 19 Mar 2018 13:15:27 +0100
From:   Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:     Scott Wood <swood@...hat.com>
Cc:     Joerg Roedel <joro@...tes.org>, iommu@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org, tglx@...utronix.de
Subject: Re: [PATCH 00/10 v2] iommu/amd: lock splitting & GFP_KERNEL
 allocation

On 2018-03-17 16:43:39 [-0500], Scott Wood wrote:
> If that's worth the lock dropping then fine (though why does only one
> of the two allocations use GFP_KERNEL?), but it doesn't need to be a
That was a mistake, I planned to keep both as GFP_KERNEL.

> raw lock if the non-allocating users are separated.  Keeping them
> separate will also preserve the WARNs if we somehow end up in an atomic
> context with no table (versus relying on atomic sleep debugging that
> may or may not be enabled), and make the code easier to understand by
> being explicit about which functions can be used from RT-atomic
> context.

That separated part is okay. We could keep it. However, I am not sure if
looking at the table irq_lookup_table[devid] without the lock is okay.
The pointer is assigned without DTE entry/iommu-flush to be completed. 
This does not look "okay".

> -Scott
> 
Sebastian