linux-kernel - [RFC 01/10] drm: Track clients by tgid and not tid

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Date:   Tue, 14 Mar 2023 14:18:55 +0000
From:   Tvrtko Ursulin <tvrtko.ursulin@...ux.intel.com>
To:     Intel-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org
Cc:     cgroups@...r.kernel.org, linux-kernel@...r.kernel.org,
        Tejun Heo <tj@...nel.org>,
        Johannes Weiner <hannes@...xchg.org>,
        Zefan Li <lizefan.x@...edance.com>,
        Dave Airlie <airlied@...hat.com>,
        Daniel Vetter <daniel.vetter@...ll.ch>,
        Rob Clark <robdclark@...omium.org>,
        Stéphane Marchesin <marcheu@...omium.org>,
        "T . J . Mercier" <tjmercier@...gle.com>, Kenny.Ho@....com,
        Christian König <christian.koenig@....com>,
        Brian Welty <brian.welty@...el.com>,
        Tvrtko Ursulin <tvrtko.ursulin@...el.com>,
        Zack Rusin <zackr@...are.com>,
        linux-graphics-maintainer@...are.com,
        Alex Deucher <alexander.deucher@....com>
Subject: [RFC 01/10] drm: Track clients by tgid and not tid

From: Tvrtko Ursulin <tvrtko.ursulin@...el.com>

Thread group id (aka pid from userspace point of view) is a more
interesting thing to show as an owner of a DRM fd, so track and show that
instead of the thread id.

In the next patch we will make the owner updated post file descriptor
handover, which will also be tgid based to avoid ping-pong when multiple
threads access the fd.

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@...el.com>
Cc: Zack Rusin <zackr@...are.com>
Cc: linux-graphics-maintainer@...are.com
Cc: Alex Deucher <alexander.deucher@....com>
Cc: "Christian König" <christian.koenig@....com>
Reviewed-by: Zack Rusin <zackr@...are.com>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c | 2 +-
 drivers/gpu/drm/drm_debugfs.c           | 4 ++--
 drivers/gpu/drm/drm_file.c              | 2 +-
 drivers/gpu/drm/vmwgfx/vmwgfx_gem.c     | 2 +-
 4 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c
index d8e683688daa..863cb668e000 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c
@@ -969,7 +969,7 @@ static int amdgpu_debugfs_gem_info_show(struct seq_file *m, void *unused)
 		 * Therefore, we need to protect this ->comm access using RCU.
 		 */
 		rcu_read_lock();
-		task = pid_task(file->pid, PIDTYPE_PID);
+		task = pid_task(file->pid, PIDTYPE_TGID);
 		seq_printf(m, "pid %8d command %s:\n", pid_nr(file->pid),
 			   task ? task->comm : "<unknown>");
 		rcu_read_unlock();
diff --git a/drivers/gpu/drm/drm_debugfs.c b/drivers/gpu/drm/drm_debugfs.c
index 4f643a490dc3..4855230ba2c6 100644
--- a/drivers/gpu/drm/drm_debugfs.c
+++ b/drivers/gpu/drm/drm_debugfs.c
@@ -80,7 +80,7 @@ static int drm_clients_info(struct seq_file *m, void *data)
 	seq_printf(m,
 		   "%20s %5s %3s master a %5s %10s\n",
 		   "command",
-		   "pid",
+		   "tgid",
 		   "dev",
 		   "uid",
 		   "magic");
@@ -94,7 +94,7 @@ static int drm_clients_info(struct seq_file *m, void *data)
 		bool is_current_master = drm_is_current_master(priv);
 
 		rcu_read_lock(); /* locks pid_task()->comm */
-		task = pid_task(priv->pid, PIDTYPE_PID);
+		task = pid_task(priv->pid, PIDTYPE_TGID);
 		uid = task ? __task_cred(task)->euid : GLOBAL_ROOT_UID;
 		seq_printf(m, "%20s %5d %3d   %c    %c %5d %10u\n",
 			   task ? task->comm : "<unknown>",
diff --git a/drivers/gpu/drm/drm_file.c b/drivers/gpu/drm/drm_file.c
index a51ff8cee049..c1018c470047 100644
--- a/drivers/gpu/drm/drm_file.c
+++ b/drivers/gpu/drm/drm_file.c
@@ -156,7 +156,7 @@ struct drm_file *drm_file_alloc(struct drm_minor *minor)
 	if (!file)
 		return ERR_PTR(-ENOMEM);
 
-	file->pid = get_pid(task_pid(current));
+	file->pid = get_pid(task_tgid(current));
 	file->minor = minor;
 
 	/* for compatibility root is always authenticated */
diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_gem.c b/drivers/gpu/drm/vmwgfx/vmwgfx_gem.c
index d6baf73a6458..c0da89e16e6f 100644
--- a/drivers/gpu/drm/vmwgfx/vmwgfx_gem.c
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_gem.c
@@ -241,7 +241,7 @@ static int vmw_debugfs_gem_info_show(struct seq_file *m, void *unused)
 		 * Therefore, we need to protect this ->comm access using RCU.
 		 */
 		rcu_read_lock();
-		task = pid_task(file->pid, PIDTYPE_PID);
+		task = pid_task(file->pid, PIDTYPE_TGID);
 		seq_printf(m, "pid %8d command %s:\n", pid_nr(file->pid),
 			   task ? task->comm : "<unknown>");
 		rcu_read_unlock();
-- 
2.37.2