video: tegra: nvmap: Don't store task struct for kernel threads

No need to maintain a reference to the task struct if the client
is a kernel thread.  In this case just set the task to NULL.

Change-Id: Ica4785388932f6b298eeb0da04b78b0e1cdc3a44
Signed-off-by: Rebecca Schultz Zavin <rebecca@android.com>

diff --git a/drivers/video/tegra/nvmap/nvmap_dev.c b/drivers/video/tegra/nvmap/nvmap_dev.c
index 7b8228a5d956ba27b760cacee89095051d2bee5a..32008e21b01ed65f632a89bc7803f22a9497b839 100644 (file)
--- a/drivers/video/tegra/nvmap/nvmap_dev.c
+++ b/drivers/video/tegra/nvmap/nvmap_dev.c
@@ -343,8 +343,11 @@ bool nvmap_shrink_carveout(struct nvmap_carveout_node *node)
                        get_client_from_carveout_commit(node, commit);
                size_t size = commit->commit;
                struct task_struct *task = client->task;
-               struct signal_struct *sig = task->signal;
+               struct signal_struct *sig;
 
+               if (!task)
+                       continue;
+               sig = task->signal;
                if (!task->mm || !sig)
                        continue;
                if (sig->oom_adj < selected_oom_adj)
@@ -526,6 +529,7 @@ struct nvmap_client *nvmap_create_client(struct nvmap_device *dev,
                                         const char *name)
 {
        struct nvmap_client *client;
+       struct task_struct *task;
        int i;
 
        if (WARN_ON(!dev))
@@ -553,7 +557,17 @@ struct nvmap_client *nvmap_create_client(struct nvmap_device *dev,
        }
 
        get_task_struct(current);
-       client->task = current;
+       task_lock(current);
+       /* don't bother to store task struct for kernel threads,
+          they can't be killed anyway */
+       if (current->flags & PF_KTHREAD) {
+               put_task_struct(current);
+               task = NULL;
+       } else {
+               task = current;
+       }
+       task_unlock(current);
+       client->task = task;
 
        spin_lock_init(&client->ref_lock);
        atomic_set(&client->count, 1);
@@ -850,7 +864,11 @@ static struct attribute_group heap_extra_attr_group = {
 
 static void client_stringify(struct nvmap_client *client, struct seq_file *s)
 {
-       char task_comm[sizeof(client->task->comm)];
+       char task_comm[TASK_COMM_LEN];
+       if (!client->task) {
+               seq_printf(s, "%8s %16s %8u", client->name, "kernel", 0);
+               return;
+       }
        get_task_comm(task_comm, client->task);
        seq_printf(s, "%8s %16s %8u", client->name, task_comm,
                   client->task->pid);