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dkim=none (message not signed) header.d=none;amd.com; dmarc=none action=none header.from=amd.com; Received: from CH0PR12MB5348.namprd12.prod.outlook.com (2603:10b6:610:d7::9) by CH0PR12MB5251.namprd12.prod.outlook.com (2603:10b6:610:d2::23) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.4500.15; Mon, 13 Sep 2021 04:00:56 +0000 Received: from CH0PR12MB5348.namprd12.prod.outlook.com ([fe80::a9b4:b52:63:7fc1]) by CH0PR12MB5348.namprd12.prod.outlook.com ([fe80::a9b4:b52:63:7fc1%8]) with mapi id 15.20.4500.018; Mon, 13 Sep 2021 04:00:56 +0000 Subject: Re: [PATCH v2] drm/amdgpu: Fix a race of IB test To: xinhui pan , amd-gfx@lists.freedesktop.org Cc: alexander.deucher@amd.com, christian.koenig@amd.com References: <20210912234817.13051-1-xinhui.pan@amd.com> From: "Lazar, Lijo" Message-ID: <886e89f7-3ba0-fb5c-4a13-d802e0c5b5dc@amd.com> Date: Mon, 13 Sep 2021 09:30:43 +0530 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.13.0 In-Reply-To: <20210912234817.13051-1-xinhui.pan@amd.com> Content-Type: text/plain; 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So use write lock. > > Signed-off-by: xinhui pan > --- > drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c > index 19323b4cce7b..be5d12ed3db1 100644 > --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c > +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c > @@ -1358,7 +1358,7 @@ static int amdgpu_debugfs_test_ib_show(struct seq_file *m, void *unused) > } > > /* Avoid accidently unparking the sched thread during GPU reset */ > - r = down_read_killable(&adev->reset_sem); > + r = down_write_killable(&adev->reset_sem); There are many ioctls and debugfs calls which takes this lock and as you know the purpose is to avoid them while there is a reset. The purpose is *not to* fix any concurrency issues those calls themselves have otherwise and fixing those concurrency issues this way is just lazy and not acceptable. This will take away any fairness given to the writer in this rw lock and that is supposed to be the reset thread. Thanks, Lijo > if (r) > return r; > > @@ -1387,7 +1387,7 @@ static int amdgpu_debugfs_test_ib_show(struct seq_file *m, void *unused) > kthread_unpark(ring->sched.thread); > } > > - up_read(&adev->reset_sem); > + up_write(&adev->reset_sem); > > pm_runtime_mark_last_busy(dev->dev); > pm_runtime_put_autosuspend(dev->dev); >