[PATCH 28/33] drm/i915: Move per-request pid from request to ctx

[Chris Wilson <chris@chris-wilson.co.uk>]

Since contexts are not currently shared between userspace processes, we
have an exact correspondence between context creator and guilty batch
submitter. Therefore we can save some per-batch work by inspecting the
context->pid upon error instead. Note that we take the context's
creator's pid rather than the file's pid in order to better track fd
passed over sockets.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
---
 drivers/gpu/drm/i915/i915_debugfs.c     | 25 ++++++++++++++++---------
 drivers/gpu/drm/i915/i915_drv.h         |  2 ++
 drivers/gpu/drm/i915/i915_gem_context.c |  4 ++++
 drivers/gpu/drm/i915/i915_gem_request.c |  5 -----
 drivers/gpu/drm/i915/i915_gem_request.h |  3 ---
 drivers/gpu/drm/i915/i915_gpu_error.c   | 13 ++++++++++---
 6 files changed, 32 insertions(+), 20 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_debugfs.c b/drivers/gpu/drm/i915/i915_debugfs.c
index 5f00d6347905..963c6d28d332 100644
--- a/drivers/gpu/drm/i915/i915_debugfs.c
+++ b/drivers/gpu/drm/i915/i915_debugfs.c
@@ -460,6 +460,8 @@ static int i915_gem_object_info(struct seq_file *m, void* data)
 	print_context_stats(m, dev_priv);
 	list_for_each_entry_reverse(file, &dev->filelist, lhead) {
 		struct file_stats stats;
+		struct drm_i915_file_private *file_priv = file->driver_priv;
+		struct drm_i915_gem_request *request;
 		struct task_struct *task;
 
 		memset(&stats, 0, sizeof(stats));
@@ -473,10 +475,17 @@ static int i915_gem_object_info(struct seq_file *m, void* data)
 		 * still alive (e.g. get_pid(current) => fork() => exit()).
 		 * Therefore, we need to protect this ->comm access using RCU.
 		 */
+		mutex_lock(&dev->struct_mutex);
+		request = list_first_entry_or_null(&file_priv->mm.request_list,
+						   struct drm_i915_gem_request,
+						   client_list);
 		rcu_read_lock();
-		task = pid_task(file->pid, PIDTYPE_PID);
+		task = pid_task(request && request->ctx->pid ?
+				request->ctx->pid : file->pid,
+				PIDTYPE_PID);
 		print_file_stats(m, task ? task->comm : "<unknown>", stats);
 		rcu_read_unlock();
+		mutex_unlock(&dev->struct_mutex);
 	}
 	mutex_unlock(&dev->filelist_mutex);
 
@@ -657,12 +666,11 @@ static int i915_gem_request_info(struct seq_file *m, void *data)
 
 		seq_printf(m, "%s requests: %d\n", engine->name, count);
 		list_for_each_entry(req, &engine->request_list, link) {
+			struct pid *pid = req->ctx->pid;
 			struct task_struct *task;
 
 			rcu_read_lock();
-			task = NULL;
-			if (req->pid)
-				task = pid_task(req->pid, PIDTYPE_PID);
+			task = pid ? pid_task(pid, PIDTYPE_PID) : NULL;
 			seq_printf(m, "    %x @ %d: %s [%d]\n",
 				   req->fence.seqno,
 				   (int) (jiffies - req->emitted_jiffies),
@@ -1951,18 +1959,17 @@ static int i915_context_status(struct seq_file *m, void *unused)
 
 	list_for_each_entry(ctx, &dev_priv->context_list, link) {
 		seq_printf(m, "HW context %u ", ctx->hw_id);
-		if (IS_ERR(ctx->file_priv)) {
-			seq_puts(m, "(deleted) ");
-		} else if (ctx->file_priv) {
-			struct pid *pid = ctx->file_priv->file->pid;
+		if (ctx->pid) {
 			struct task_struct *task;
 
-			task = get_pid_task(pid, PIDTYPE_PID);
+			task = get_pid_task(ctx->pid, PIDTYPE_PID);
 			if (task) {
 				seq_printf(m, "(%s [%d]) ",
 					   task->comm, task->pid);
 				put_task_struct(task);
 			}
+		} else if (IS_ERR(ctx->file_priv)) {
+			seq_puts(m, "(deleted) ");
 		} else {
 			seq_puts(m, "(kernel) ");
 		}
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 4023718017a8..e7357656728e 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -560,6 +560,7 @@ struct drm_i915_error_state {
 
 		struct drm_i915_error_request {
 			long jiffies;
+			pid_t pid;
 			u32 seqno;
 			u32 tail;
 		} *requests;
@@ -880,6 +881,7 @@ struct i915_gem_context {
 	struct drm_i915_private *i915;
 	struct drm_i915_file_private *file_priv;
 	struct i915_hw_ppgtt *ppgtt;
+	struct pid *pid;
 
 	struct i915_ctx_hang_stats hang_stats;
 
diff --git a/drivers/gpu/drm/i915/i915_gem_context.c b/drivers/gpu/drm/i915/i915_gem_context.c
index 15eed897b498..c026d591d142 100644
--- a/drivers/gpu/drm/i915/i915_gem_context.c
+++ b/drivers/gpu/drm/i915/i915_gem_context.c
@@ -158,6 +158,7 @@ void i915_gem_context_free(struct kref *ctx_ref)
 		i915_gem_object_put(ce->state->obj);
 	}
 
+	put_pid(ctx->pid);
 	list_del(&ctx->link);
 
 	ida_simple_remove(&ctx->i915->context_hw_ida, ctx->hw_id);
@@ -311,6 +312,9 @@ __create_hw_context(struct drm_device *dev,
 		ret = DEFAULT_CONTEXT_HANDLE;
 
 	ctx->file_priv = file_priv;
+	if (file_priv)
+		ctx->pid = get_task_pid(current, PIDTYPE_PID);
+
 	ctx->user_handle = ret;
 	/* NB: Mark all slices as needing a remap so that when the context first
 	 * loads it will restore whatever remap state already exists. If there
diff --git a/drivers/gpu/drm/i915/i915_gem_request.c b/drivers/gpu/drm/i915/i915_gem_request.c
index 187c4f9ce8d0..8fdd313248f9 100644
--- a/drivers/gpu/drm/i915/i915_gem_request.c
+++ b/drivers/gpu/drm/i915/i915_gem_request.c
@@ -137,8 +137,6 @@ int i915_gem_request_add_to_client(struct drm_i915_gem_request *req,
 	list_add_tail(&req->client_list, &file_priv->mm.request_list);
 	spin_unlock(&file_priv->mm.lock);
 
-	req->pid = get_pid(task_pid(current));
-
 	return 0;
 }
 
@@ -154,9 +152,6 @@ i915_gem_request_remove_from_client(struct drm_i915_gem_request *request)
 	list_del(&request->client_list);
 	request->file_priv = NULL;
 	spin_unlock(&file_priv->mm.lock);
-
-	put_pid(request->pid);
-	request->pid = NULL;
 }
 
 void i915_gem_retire_noop(struct i915_gem_active *active,
diff --git a/drivers/gpu/drm/i915/i915_gem_request.h b/drivers/gpu/drm/i915/i915_gem_request.h
index 1f396f470a86..72a4b73cbb79 100644
--- a/drivers/gpu/drm/i915/i915_gem_request.h
+++ b/drivers/gpu/drm/i915/i915_gem_request.h
@@ -134,9 +134,6 @@ struct drm_i915_gem_request {
 	/** file_priv list entry for this request */
 	struct list_head client_list;
 
-	/** process identifier submitting this request */
-	struct pid *pid;
-
 	/**
 	 * The ELSP only accepts two elements at a time, so we queue
 	 * context/tail pairs on a given queue (ring->execlist_queue) until the
diff --git a/drivers/gpu/drm/i915/i915_gpu_error.c b/drivers/gpu/drm/i915/i915_gpu_error.c
index 9faac19029cd..52d1564f37c4 100644
--- a/drivers/gpu/drm/i915/i915_gpu_error.c
+++ b/drivers/gpu/drm/i915/i915_gpu_error.c
@@ -460,7 +460,8 @@ int i915_error_state_to_str(struct drm_i915_error_state_buf *m,
 				   dev_priv->engine[i].name,
 				   ee->num_requests);
 			for (j = 0; j < ee->num_requests; j++) {
-				err_printf(m, "  seqno 0x%08x, emitted %ld, tail 0x%08x\n",
+				err_printf(m, "  pid %d, seqno 0x%08x, emitted %ld, tail 0x%08x\n",
+					   ee->requests[j].pid,
 					   ee->requests[j].seqno,
 					   ee->requests[j].jiffies,
 					   ee->requests[j].tail);
@@ -1061,6 +1062,7 @@ static void i915_gem_record_rings(struct drm_i915_private *dev_priv,
 		request = i915_gem_find_active_request(engine);
 		if (request) {
 			struct intel_ring *ring;
+			struct pid *pid;
 
 			ee->vm = request->ctx->ppgtt ?
 				&request->ctx->ppgtt->base : &ggtt->base;
@@ -1082,11 +1084,12 @@ static void i915_gem_record_rings(struct drm_i915_private *dev_priv,
 				i915_error_object_create(dev_priv,
 							 request->ctx->engine[i].state);
 
-			if (request->pid) {
+			pid = request->ctx->pid;
+			if (pid) {
 				struct task_struct *task;
 
 				rcu_read_lock();
-				task = pid_task(request->pid, PIDTYPE_PID);
+				task = pid_task(pid, PIDTYPE_PID);
 				if (task) {
 					strcpy(ee->comm, task->comm);
 					ee->pid = task->pid;
@@ -1150,6 +1153,10 @@ static void i915_gem_record_rings(struct drm_i915_private *dev_priv,
 			erq->seqno = request->fence.seqno;
 			erq->jiffies = request->emitted_jiffies;
 			erq->tail = request->postfix;
+
+			rcu_read_lock();
+			erq->pid = request->ctx ? pid_nr(request->ctx->pid) : 0;
+			rcu_read_unlock();
 		}
 	}
 }
-- 
2.8.1

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