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From: Andrew Morton <akpm@linux-foundation.org>
To: Alex Sierra <alex.sierra@amd.com>
Cc: <jgg@nvidia.com>, <david@redhat.com>, <Felix.Kuehling@amd.com>,
	<linux-mm@kvack.org>, <rcampbell@nvidia.com>,
	<linux-ext4@vger.kernel.org>, <linux-xfs@vger.kernel.org>,
	<amd-gfx@lists.freedesktop.org>,
	<dri-devel@lists.freedesktop.org>, <hch@lst.de>,
	<jglisse@redhat.com>, <apopple@nvidia.com>, <willy@infradead.org>
Subject: Re: [PATCH v4 07/13] lib: test_hmm add ioctl to get zone device type
Date: Tue, 31 May 2022 10:31:52 -0700	[thread overview]
Message-ID: <20220531103152.6b9214cc39a87020d7d7927b@linux-foundation.org> (raw)
In-Reply-To: <20220531155629.20057-8-alex.sierra@amd.com>

On Tue, 31 May 2022 10:56:23 -0500 Alex Sierra <alex.sierra@amd.com> wrote:

> new ioctl cmd added to query zone device type. This will be
> used once the test_hmm adds zone device coherent type.
> 
> @@ -1026,6 +1027,15 @@ static int dmirror_snapshot(struct dmirror *dmirror,
>  	return ret;
>  }
>  
> +static int dmirror_get_device_type(struct dmirror *dmirror,
> +			    struct hmm_dmirror_cmd *cmd)
> +{
> +	mutex_lock(&dmirror->mutex);
> +	cmd->zone_device_type = dmirror->mdevice->zone_device_type;
> +	mutex_unlock(&dmirror->mutex);

What does the locking here do?

Presumably cmd->zone_device_type can become out of date the instant the
mutex is released, so what was the point in taking the mutex?

And does it make sense to return potentially out-of-date info to
userspace?  Perhaps this interface simply shouldn't exist?

WARNING: multiple messages have this Message-ID (diff)
From: Andrew Morton <akpm@linux-foundation.org>
To: Alex Sierra <alex.sierra@amd.com>
Cc: rcampbell@nvidia.com, willy@infradead.org, david@redhat.com,
	Felix.Kuehling@amd.com, apopple@nvidia.com,
	amd-gfx@lists.freedesktop.org, linux-xfs@vger.kernel.org,
	linux-mm@kvack.org, jglisse@redhat.com,
	dri-devel@lists.freedesktop.org, jgg@nvidia.com,
	linux-ext4@vger.kernel.org, hch@lst.de
Subject: Re: [PATCH v4 07/13] lib: test_hmm add ioctl to get zone device type
Date: Tue, 31 May 2022 10:31:52 -0700	[thread overview]
Message-ID: <20220531103152.6b9214cc39a87020d7d7927b@linux-foundation.org> (raw)
In-Reply-To: <20220531155629.20057-8-alex.sierra@amd.com>

On Tue, 31 May 2022 10:56:23 -0500 Alex Sierra <alex.sierra@amd.com> wrote:

> new ioctl cmd added to query zone device type. This will be
> used once the test_hmm adds zone device coherent type.
> 
> @@ -1026,6 +1027,15 @@ static int dmirror_snapshot(struct dmirror *dmirror,
>  	return ret;
>  }
>  
> +static int dmirror_get_device_type(struct dmirror *dmirror,
> +			    struct hmm_dmirror_cmd *cmd)
> +{
> +	mutex_lock(&dmirror->mutex);
> +	cmd->zone_device_type = dmirror->mdevice->zone_device_type;
> +	mutex_unlock(&dmirror->mutex);

What does the locking here do?

Presumably cmd->zone_device_type can become out of date the instant the
mutex is released, so what was the point in taking the mutex?

And does it make sense to return potentially out-of-date info to
userspace?  Perhaps this interface simply shouldn't exist?

  reply	other threads:[~2022-05-31 17:31 UTC|newest]

Thread overview: 32+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-05-31 15:56 [PATCH v4 00/13] Add MEMORY_DEVICE_COHERENT for coherent device memory mapping Alex Sierra
2022-05-31 15:56 ` Alex Sierra
2022-05-31 15:56 ` [PATCH v4 01/13] mm: add zone device coherent type memory support Alex Sierra
2022-05-31 15:56   ` Alex Sierra
2022-05-31 15:56 ` [PATCH v4 02/13] mm: handling Non-LRU pages returned by vm_normal_pages Alex Sierra
2022-05-31 15:56   ` Alex Sierra
2022-05-31 15:56 ` [PATCH v4 03/13] mm: add device coherent vma selection for memory migration Alex Sierra
2022-05-31 15:56   ` Alex Sierra
2022-05-31 15:56 ` [PATCH v4 04/13] mm: remove the vma check in migrate_vma_setup() Alex Sierra
2022-05-31 15:56   ` Alex Sierra
2022-05-31 15:56 ` [PATCH v4 05/13] mm/gup: migrate device coherent pages when pinning instead of failing Alex Sierra
2022-05-31 15:56   ` Alex Sierra
2022-05-31 15:56 ` [PATCH v4 06/13] drm/amdkfd: add SPM support for SVM Alex Sierra
2022-05-31 15:56   ` Alex Sierra
2022-05-31 15:56 ` [PATCH v4 07/13] lib: test_hmm add ioctl to get zone device type Alex Sierra
2022-05-31 15:56   ` Alex Sierra
2022-05-31 17:31   ` Andrew Morton [this message]
2022-05-31 17:31     ` Andrew Morton
2022-05-31 19:19     ` Sierra Guiza, Alejandro (Alex)
2022-05-31 19:19       ` Sierra Guiza, Alejandro (Alex)
2022-05-31 15:56 ` [PATCH v4 08/13] lib: test_hmm add module param for " Alex Sierra
2022-05-31 15:56   ` Alex Sierra
2022-05-31 15:56 ` [PATCH v4 09/13] lib: add support for device coherent type in test_hmm Alex Sierra
2022-05-31 15:56   ` Alex Sierra
2022-05-31 15:56 ` [PATCH v4 10/13] tools: update hmm-test to support device coherent type Alex Sierra
2022-05-31 15:56   ` Alex Sierra
2022-05-31 15:56 ` [PATCH v4 11/13] tools: update test_hmm script to support SP config Alex Sierra
2022-05-31 15:56   ` Alex Sierra
2022-05-31 15:56 ` [PATCH v4 12/13] tools: add hmm gup tests for device coherent type Alex Sierra
2022-05-31 15:56   ` Alex Sierra
2022-05-31 15:56 ` [PATCH v4 13/13] tools: add selftests to hmm for COW in device memory Alex Sierra
2022-05-31 15:56   ` Alex Sierra

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