drm/xe: Store process name and pid in xe file

An xe file can outlive the associated process as the GPU cleanup is just
triggered upon file close (process kill) and completes sometime later.
If the file close triggers error conditions (GPU hangs) the process
cannot be safely referenced to retrieve the name and pid for debug
information. Store the process name and pid directly in the xe file to
be safe.

v2:
 - Access file->pid via rcu_access_pointer (Matthew Auld)

Fixes: b10d0c5e ("drm/xe: Add process name to devcoredump")
Fixes: f6ca930d ("drm/xe: Add process name and PID to job timedout message")
Signed-off-by: Matthew Brost <matthew.brost@intel.com>
Acked-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240723151045.1725417-1-matthew.brost@intel.com

drivers/gpu/drm/xe/xe_devcoredump.c

@@ -171,7 +171,6 @@ static void devcoredump_snapshot(struct xe_devcoredump *coredump,
 	u32 adj_logical_mask = q->logical_mask;
 	u32 width_mask = (0x1 << q->width) - 1;
 	const char *process_name = "no process";
-	struct task_struct *task = NULL;
 
 	int i;
 	bool cookie;
@@ -179,14 +178,9 @@ static void devcoredump_snapshot(struct xe_devcoredump *coredump,
 	ss->snapshot_time = ktime_get_real();
 	ss->boot_time = ktime_get_boottime();
 
-	if (q->vm && q->vm->xef) {
-		task = get_pid_task(q->vm->xef->drm->pid, PIDTYPE_PID);
-		if (task)
-			process_name = task->comm;
-	}
+	if (q->vm && q->vm->xef)
+		process_name = q->vm->xef->process_name;
 	strscpy(ss->process_name, process_name);
-	if (task)
-		put_task_struct(task);
 
 	ss->gt = q->gt;
 	INIT_WORK(&ss->work, xe_devcoredump_deferred_snap_work);

drivers/gpu/drm/xe/xe_device.c

@@ -64,6 +64,7 @@ static int xe_file_open(struct drm_device *dev, struct drm_file *file)
 	struct xe_drm_client *client;
 	struct xe_file *xef;
 	int ret = -ENOMEM;
+	struct task_struct *task = NULL;
 
 	xef = kzalloc(sizeof(*xef), GFP_KERNEL);
 	if (!xef)
@@ -92,6 +93,13 @@ static int xe_file_open(struct drm_device *dev, struct drm_file *file)
 	file->driver_priv = xef;
 	kref_init(&xef->refcount);
 
+	task = get_pid_task(rcu_access_pointer(file->pid), PIDTYPE_PID);
+	if (task) {
+		xef->process_name = kstrdup(task->comm, GFP_KERNEL);
+		xef->pid = task->pid;
+		put_task_struct(task);
+	}
+
 	return 0;
 }
 
@@ -110,6 +118,7 @@ static void xe_file_destroy(struct kref *ref)
 	spin_unlock(&xe->clients.lock);
 
 	xe_drm_client_put(xef->client);
+	kfree(xef->process_name);
 	kfree(xef);
 }
 

drivers/gpu/drm/xe/xe_device_types.h

@@ -582,6 +582,18 @@ struct xe_file {
 	/** @client: drm client */
 	struct xe_drm_client *client;
 
+	/**
+	 * @process_name: process name for file handle, used to safely output
+	 * during error situations where xe file can outlive process
+	 */
+	char *process_name;
+
+	/**
+	 * @pid: pid for file handle, used to safely output uring error
+	 * situations where xe file can outlive process
+	 */
+	pid_t pid;
+
 	/** @refcount: ref count of this xe file */
 	struct kref refcount;
 };

drivers/gpu/drm/xe/xe_guc_submit.c

@@ -1072,7 +1072,6 @@ guc_exec_queue_timedout_job(struct drm_sched_job *drm_job)
 	struct xe_gpu_scheduler *sched = &q->guc->sched;
 	struct xe_guc *guc = exec_queue_to_guc(q);
 	const char *process_name = "no process";
-	struct task_struct *task = NULL;
 	int err = -ETIME;
 	pid_t pid = -1;
 	int i = 0;
@@ -1172,17 +1171,12 @@ guc_exec_queue_timedout_job(struct drm_sched_job *drm_job)
 	}
 
 	if (q->vm && q->vm->xef) {
-		task = get_pid_task(q->vm->xef->drm->pid, PIDTYPE_PID);
-		if (task) {
-			process_name = task->comm;
-			pid = task->pid;
-		}
+		process_name = q->vm->xef->process_name;
+		pid = q->vm->xef->pid;
 	}
 	xe_gt_notice(guc_to_gt(guc), "Timedout job: seqno=%u, lrc_seqno=%u, guc_id=%d, flags=0x%lx in %s [%d]",
 		     xe_sched_job_seqno(job), xe_sched_job_lrc_seqno(job),
 		     q->guc->id, q->flags, process_name, pid);
-	if (task)
-		put_task_struct(task);
 
 	trace_xe_sched_job_timedout(job);