From: Steven Price <steven.price@arm.com>
To: Boris Brezillon <boris.brezillon@collabora.com>
Cc: stable@vger.kernel.org, dri-devel@lists.freedesktop.org,
Rob Herring <robh+dt@kernel.org>,
Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Subject: Re: [PATCH 2/8] drm/panfrost: Fix a race in panfrost_ioctl_madvise()
Date: Fri, 29 Nov 2019 14:40:34 +0000 [thread overview]
Message-ID: <b159591d-1dd4-1ac7-e924-c02be1d8b1f3@arm.com> (raw)
In-Reply-To: <20191129153310.2f9c80e1@collabora.com>
On 29/11/2019 14:33, Boris Brezillon wrote:
> On Fri, 29 Nov 2019 14:24:48 +0000
> Steven Price <steven.price@arm.com> wrote:
>
>> On 29/11/2019 13:59, Boris Brezillon wrote:
>>> If 2 threads change the MADVISE property of the same BO in parallel we
>>> might end up with an shmem->madv value that's inconsistent with the
>>> presence of the BO in the shrinker list.
>>
>> I'm a bit worried from the point of view of user space sanity that you
>> observed this - but clearly the kernel should be robust!
>
> It's not something I observed, just found the race by inspecting the
> code, and I thought it was worth fixing it.
Good! ;) Your cover letter referring to a "debug session" made me think
you'd actually hit all these.
Steve
>>
>>>
>>> The easiest solution to fix that is to protect the
>>> drm_gem_shmem_madvise() call with the shrinker lock.
>>>
>>> Fixes: 013b65101315 ("drm/panfrost: Add madvise and shrinker support")
>>> Cc: <stable@vger.kernel.org>
>>> Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>
>>
>> Reviewed-by: Steven Price <steven.price@arm.com>
>
> Thanks.
>
>>
>>> ---
>>> drivers/gpu/drm/panfrost/panfrost_drv.c | 9 ++++-----
>>> 1 file changed, 4 insertions(+), 5 deletions(-)
>>>
>>> diff --git a/drivers/gpu/drm/panfrost/panfrost_drv.c b/drivers/gpu/drm/panfrost/panfrost_drv.c
>>> index f21bc8a7ee3a..efc0a24d1f4c 100644
>>> --- a/drivers/gpu/drm/panfrost/panfrost_drv.c
>>> +++ b/drivers/gpu/drm/panfrost/panfrost_drv.c
>>> @@ -347,20 +347,19 @@ static int panfrost_ioctl_madvise(struct drm_device *dev, void *data,
>>> return -ENOENT;
>>> }
>>>
>>> + mutex_lock(&pfdev->shrinker_lock);
>>> args->retained = drm_gem_shmem_madvise(gem_obj, args->madv);
>>>
>>> if (args->retained) {
>>> struct panfrost_gem_object *bo = to_panfrost_bo(gem_obj);
>>>
>>> - mutex_lock(&pfdev->shrinker_lock);
>>> -
>>> if (args->madv == PANFROST_MADV_DONTNEED)
>>> - list_add_tail(&bo->base.madv_list, &pfdev->shrinker_list);
>>> + list_add_tail(&bo->base.madv_list,
>>> + &pfdev->shrinker_list);
>>> else if (args->madv == PANFROST_MADV_WILLNEED)
>>> list_del_init(&bo->base.madv_list);
>>> -
>>> - mutex_unlock(&pfdev->shrinker_lock);
>>> }
>>> + mutex_unlock(&pfdev->shrinker_lock);
>>>
>>> drm_gem_object_put_unlocked(gem_obj);
>>> return 0;
>>>
>>
>
> _______________________________________________
> dri-devel mailing list
> dri-devel@lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/dri-devel
>
next prev parent reply other threads:[~2019-11-29 14:40 UTC|newest]
Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20191129135908.2439529-1-boris.brezillon@collabora.com>
2019-11-29 13:59 ` [PATCH 1/8] drm/panfrost: Make panfrost_job_run() return an ERR_PTR() instead of NULL Boris Brezillon
2019-11-29 14:19 ` Steven Price
2019-11-29 14:31 ` Boris Brezillon
2019-11-29 14:38 ` Steven Price
2019-11-29 19:32 ` Boris Brezillon
2019-11-29 13:59 ` [PATCH 2/8] drm/panfrost: Fix a race in panfrost_ioctl_madvise() Boris Brezillon
2019-11-29 14:24 ` Steven Price
2019-11-29 14:33 ` Boris Brezillon
2019-11-29 14:40 ` Steven Price [this message]
2019-11-29 20:07 ` Daniel Vetter
2019-11-29 21:45 ` Boris Brezillon
2019-12-05 23:08 ` Rob Herring
2019-12-06 7:53 ` Boris Brezillon
2019-12-06 8:08 ` Boris Brezillon
2019-11-29 13:59 ` [PATCH 3/8] drm/panfrost: Fix a BO leak in panfrost_ioctl_mmap_bo() Boris Brezillon
2019-11-29 14:26 ` Steven Price
2019-11-29 13:59 ` [PATCH 4/8] drm/panfrost: Fix a race in panfrost_gem_free_object() Boris Brezillon
2019-11-29 14:28 ` Steven Price
2019-11-29 13:59 ` [PATCH 5/8] drm/panfrost: Open/close the perfcnt BO Boris Brezillon
2019-11-29 14:34 ` Steven Price
2019-11-29 13:59 ` [PATCH 6/8] drm/panfrost: Make sure imported/exported BOs are never purged Boris Brezillon
2019-11-29 14:14 ` Boris Brezillon
2019-11-29 14:45 ` Steven Price
2019-11-29 14:52 ` Boris Brezillon
2019-11-29 20:12 ` Daniel Vetter
2019-11-29 21:09 ` Boris Brezillon
2019-12-02 8:52 ` Daniel Vetter
2019-12-02 9:50 ` Boris Brezillon
2019-11-29 13:59 ` [PATCH 7/8] drm/panfrost: Add the panfrost_gem_mapping concept Boris Brezillon
2019-11-29 15:37 ` Steven Price
2019-11-29 20:14 ` Daniel Vetter
2019-11-29 21:36 ` Boris Brezillon
2019-12-02 8:55 ` Daniel Vetter
2019-12-02 9:13 ` Boris Brezillon
2019-12-02 9:44 ` Daniel Vetter
2019-12-04 11:41 ` Steven Price
2019-11-29 13:59 ` [PATCH 8/8] drm/panfrost: Make sure the shrinker does not reclaim referenced BOs Boris Brezillon
2019-11-29 15:48 ` Steven Price
2019-11-29 16:07 ` Boris Brezillon
2019-11-29 16:12 ` Steven Price
2019-12-02 12:50 ` Robin Murphy
2019-12-02 13:32 ` Boris Brezillon
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=b159591d-1dd4-1ac7-e924-c02be1d8b1f3@arm.com \
--to=steven.price@arm.com \
--cc=alyssa.rosenzweig@collabora.com \
--cc=boris.brezillon@collabora.com \
--cc=dri-devel@lists.freedesktop.org \
--cc=robh+dt@kernel.org \
--cc=stable@vger.kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).