[PATCH v2] drm/xe: Store process name and pid in xe file

[Matthew Brost]

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)

Signed-off-by: Matthew Brost <matthew.brost at intel.com>
Reviewed-by: Matthew Auld <matthew.auld at intel.com>
---
 drivers/gpu/drm/xe/xe_devcoredump.c  | 10 ++--------
 drivers/gpu/drm/xe/xe_device.c       |  9 +++++++++
 drivers/gpu/drm/xe/xe_device_types.h | 12 ++++++++++++
 drivers/gpu/drm/xe/xe_guc_submit.c   | 10 ++--------
 4 files changed, 25 insertions(+), 16 deletions(-)

diff --git a/drivers/gpu/drm/xe/xe_devcoredump.c b/drivers/gpu/drm/xe/xe_devcoredump.c
index 62c2b10fbf1d..d8d8ca2c19d3 100644
--- a/drivers/gpu/drm/xe/xe_devcoredump.c
+++ b/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);
diff --git a/drivers/gpu/drm/xe/xe_device.c b/drivers/gpu/drm/xe/xe_device.c
index b677608eb592..1aba6f9eaa19 100644
--- a/drivers/gpu/drm/xe/xe_device.c
+++ b/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);
 }
 
diff --git a/drivers/gpu/drm/xe/xe_device_types.h b/drivers/gpu/drm/xe/xe_device_types.h
index 36252d5b1663..5b7292a9a66d 100644
--- a/drivers/gpu/drm/xe/xe_device_types.h
+++ b/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;
 };
diff --git a/drivers/gpu/drm/xe/xe_guc_submit.c b/drivers/gpu/drm/xe/xe_guc_submit.c
index da2ead86b9ae..a4570631926f 100644
--- a/drivers/gpu/drm/xe/xe_guc_submit.c
+++ b/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);
 
-- 
2.34.1