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Tue, 21 Apr 2020 07:41:56 +0000 Subject: Re: [PATCH V4] amdgpu: reduce no need mutex_lock area To: 1587181464-114215-1-git-send-email-bernard@vivo.com, Felix Kuehling , Alex Deucher , "David (ChunMing) Zhou" , David Airlie , Daniel Vetter , amd-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org Cc: opensource.kernel@vivo.com, Bernard Zhao References: <20200421073621.129690-1-bernard@vivo.com> From: =?UTF-8?Q?Christian_K=c3=b6nig?= Message-ID: Date: Tue, 21 Apr 2020 09:41:27 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.9.0 In-Reply-To: <20200421073621.129690-1-bernard@vivo.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US X-ClientProxiedBy: FR2P281CA0008.DEUP281.PROD.OUTLOOK.COM (2603:10a6:d10:a::18) To DM6PR12MB4401.namprd12.prod.outlook.com (2603:10b6:5:2a9::15) MIME-Version: 1.0 X-MS-Exchange-MessageSentRepresentingType: 1 Received: from [IPv6:2a02:908:1252:fb60:be8a:bd56:1f94:86e7] (2a02:908:1252:fb60:be8a:bd56:1f94:86e7) by FR2P281CA0008.DEUP281.PROD.OUTLOOK.COM (2603:10a6:d10:a::18) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.2921.29 via Frontend Transport; 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X-Microsoft-Antispam-Message-Info: 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 X-MS-Exchange-AntiSpam-MessageData: 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 X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-Network-Message-Id: 3531881c-3955-4140-0f8e-08d7e5c77740 X-MS-Exchange-CrossTenant-OriginalArrivalTime: 21 Apr 2020 07:41:56.0991 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 3dd8961f-e488-4e60-8e11-a82d994e183d X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: f2e/SmAGHaMn8fpMW71kAoBnRsbVoVTa+oZp4ddrF3pqTI7BlOXaKiEI0n0etgxD X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM6PR12MB3531 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Am 21.04.20 um 09:36 schrieb Bernard Zhao: > Maybe we could reduce the mutex_lock(&mem->lock)`s protected code area, > and no need to protect pr_debug. Well that change looks rather superfluous to me. This is for freeing memory which by definition can only be done once and so the should be exactly zero contention on the lock except in a case of an error. Regards, Christian. > > Signed-off-by: Bernard Zhao > > Changes since V1: > *commit message improve > > Changes since V2: > *move comment along with the mutex_unlock > > Changes since V3: > *lock protect the if check, there is some possibility of multi-threaded > racing modify. > > Link for V1: > *https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Flore.kernel.org%2Fpatchwork%2Fpatch%2F1226588%2F&data=02%7C01%7Cchristian.koenig%40amd.com%7C9f2b2080f4174c421e4f08d7e5c6b899%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637230513976133424&sdata=6wezM%2F%2FjM5uuLblJejS9XFlE9DjWQ5zSt5PsqrfvCVo%3D&reserved=0 > --- > drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c > index 327317c54f7c..549bdb429883 100644 > --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c > +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c > @@ -1289,9 +1289,9 @@ int amdgpu_amdkfd_gpuvm_free_memory_of_gpu( > mutex_lock(&mem->lock); > > if (mem->mapped_to_gpu_memory > 0) { > + mutex_unlock(&mem->lock); > pr_debug("BO VA 0x%llx size 0x%lx is still mapped.\n", > mem->va, bo_size); > - mutex_unlock(&mem->lock); > return -EBUSY; > } >