linux-kernel - Re: [PATCH 1/6] dma-buf/dma-fence: Add dma_fence_test_signaled

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <adfd840e-fcc8-4cdb-8fd8-d0e48ee32247@amd.com>
Date: Thu, 27 Nov 2025 11:01:06 +0100
From: Christian König <christian.koenig@....com>
To: phasta@...nel.org, Matthew Brost <matthew.brost@...el.com>
Cc: Sumit Semwal <sumit.semwal@...aro.org>,
 Gustavo Padovan <gustavo@...ovan.org>,
 Felix Kuehling <Felix.Kuehling@....com>,
 Alex Deucher <alexander.deucher@....com>, David Airlie <airlied@...il.com>,
 Simona Vetter <simona@...ll.ch>, Jani Nikula <jani.nikula@...ux.intel.com>,
 Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
 Rodrigo Vivi <rodrigo.vivi@...el.com>, Tvrtko Ursulin
 <tursulin@...ulin.net>, Huang Rui <ray.huang@....com>,
 Matthew Auld <matthew.auld@...el.com>,
 Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
 Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>,
 Lucas De Marchi <lucas.demarchi@...el.com>,
 Thomas Hellström <thomas.hellstrom@...ux.intel.com>,
 linux-media@...r.kernel.org, dri-devel@...ts.freedesktop.org,
 linaro-mm-sig@...ts.linaro.org, linux-kernel@...r.kernel.org,
 amd-gfx@...ts.freedesktop.org, intel-gfx@...ts.freedesktop.org,
 intel-xe@...ts.freedesktop.org, rust-for-linux@...r.kernel.org,
 Tvrtko Ursulin <tvrtko.ursulin@...lia.com>
Subject: Re: [PATCH 1/6] dma-buf/dma-fence: Add dma_fence_test_signaled_flag()

On 11/27/25 10:16, Philipp Stanner wrote:
> On Thu, 2025-11-27 at 09:11 +0100, Christian König wrote:
>> On 11/26/25 17:55, Matthew Brost wrote:
>>> On Wed, Nov 26, 2025 at 08:41:27AM -0800, Matthew Brost wrote:
>>>> On Wed, Nov 26, 2025 at 02:19:10PM +0100, Philipp Stanner wrote:
>>>>> The dma_fence framework checks at many places whether the signaled flag
>>>>> of a fence is already set. The code can be simplified and made more
>>>>> readable by providing a helper function for that.
>>>>>
>>>>> Add dma_fence_test_signaled_flag(), which only checks whether a fence is
>>>>> signaled. Use it internally.
>>>>>
>>>>> Suggested-by: Tvrtko Ursulin <tvrtko.ursulin@...lia.com>
>>>>> Signed-off-by: Philipp Stanner <phasta@...nel.org>
>>>>
>>>> This is a nice cleanp:
>>>> Reviewed-by: Matthew Brost <matthew.brost@...el.com>
>>>>
>>>>> ---
>>>>>  drivers/dma-buf/dma-fence.c | 19 +++++++++----------
>>>>>  include/linux/dma-fence.h   | 24 ++++++++++++++++++++++--
>>>>>  2 files changed, 31 insertions(+), 12 deletions(-)
>>>>>
>>>>> diff --git a/drivers/dma-buf/dma-fence.c b/drivers/dma-buf/dma-fence.c
>>>>> index 39e6f93dc310..25117a906846 100644
>>>>> --- a/drivers/dma-buf/dma-fence.c
>>>>> +++ b/drivers/dma-buf/dma-fence.c
>>>>> @@ -372,8 +372,7 @@ int dma_fence_signal_timestamp_locked(struct dma_fence *fence,
>>>>>  
>>>>>  	lockdep_assert_held(fence->lock);
>>>>>  
>>>>> -	if (unlikely(test_and_set_bit(DMA_FENCE_FLAG_SIGNALED_BIT,
>>>>> -				      &fence->flags)))
>>>
>>> I need to read a little better, I think this change isn't quite right.
>>> The original code is test and set, the updated code is test only (i.e.,
>>> you are missing the set step). So maybe just leave this line as is.
>>
>> Oh, good point! I've totally missed that as well.
> 
> Oh dear; I also just saw it when opening the mail client ._.
> 
>>
>> But that means that this patch set hasn't even been smoke tested.
> 
> I've built it and did some basic testing with my Nouveau system. Any
> suggestions? Do you have a CI that one can trigger?

DMA-buf has CONFIG_DMABUF_SELFTESTS which should be able to catch things like that.

But even running Nouveau should have found this since basically no fence at would signal any more.

Regards,
Christian.

> 
> Thx
> P.