ion:synchronize debugfs callback and ion_client_destroy

There are race condition B/T ion_client_destroy and debugfs callbacks.
Let's use a mutex to synchronize them.

Signed-off-by: Neil Zhang <neilzhang1123@hotmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/staging/android/ion/ion.c b/drivers/staging/android/ion/ion.c
index d669848..7ff2a7e 100644 (file)
--- a/drivers/staging/android/ion/ion.c
+++ b/drivers/staging/android/ion/ion.c
@@ -677,6 +677,34 @@ void ion_unmap_kernel(struct ion_client *client, struct ion_handle *handle)
 }
 EXPORT_SYMBOL(ion_unmap_kernel);
 
+static struct mutex debugfs_mutex;
+static struct rb_root *ion_root_client;
+static int is_client_alive(struct ion_client *client)
+{
+       struct rb_node *node;
+       struct ion_client *tmp;
+       struct ion_device *dev;
+
+       node = ion_root_client->rb_node;
+       dev = container_of(ion_root_client, struct ion_device, clients);
+
+       down_read(&dev->lock);
+       while (node) {
+               tmp = rb_entry(node, struct ion_client, node);
+               if (client < tmp) {
+                       node = node->rb_left;
+               } else if (client > tmp) {
+                       node = node->rb_right;
+               } else {
+                       up_read(&dev->lock);
+                       return 1;
+               }
+       }
+
+       up_read(&dev->lock);
+       return 0;
+}
+
 static int ion_debug_client_show(struct seq_file *s, void *unused)
 {
        struct ion_client *client = s->private;
@@ -685,6 +713,14 @@ static int ion_debug_client_show(struct seq_file *s, void *unused)
        const char *names[ION_NUM_HEAP_IDS] = {NULL};
        int i;
 
+       mutex_lock(&debugfs_mutex);
+       if (!is_client_alive(client)) {
+               seq_printf(s, "ion_client 0x%p dead, can't dump its buffers\n",
+                          client);
+               mutex_unlock(&debugfs_mutex);
+               return 0;
+       }
+
        mutex_lock(&client->lock);
        for (n = rb_first(&client->handles); n; n = rb_next(n)) {
                struct ion_handle *handle = rb_entry(n, struct ion_handle,
@@ -696,6 +732,7 @@ static int ion_debug_client_show(struct seq_file *s, void *unused)
                sizes[id] += handle->buffer->size;
        }
        mutex_unlock(&client->lock);
+       mutex_unlock(&debugfs_mutex);
 
        seq_printf(s, "%16.16s: %16.16s\n", "heap_name", "size_in_bytes");
        for (i = 0; i < ION_NUM_HEAP_IDS; i++) {
@@ -832,6 +869,7 @@ void ion_client_destroy(struct ion_client *client)
        struct rb_node *n;
 
        pr_debug("%s: %d\n", __func__, __LINE__);
+       mutex_lock(&debugfs_mutex);
        while ((n = rb_first(&client->handles))) {
                struct ion_handle *handle = rb_entry(n, struct ion_handle,
                                                     node);
@@ -850,6 +888,7 @@ void ion_client_destroy(struct ion_client *client)
        kfree(client->display_name);
        kfree(client->name);
        kfree(client);
+       mutex_unlock(&debugfs_mutex);
 }
 EXPORT_SYMBOL(ion_client_destroy);
 
@@ -1415,6 +1454,7 @@ static int ion_debug_heap_show(struct seq_file *s, void *unused)
        seq_printf(s, "%16s %16s %16s\n", "client", "pid", "size");
        seq_puts(s, "----------------------------------------------------\n");
 
+       mutex_lock(&debugfs_mutex);
        for (n = rb_first(&dev->clients); n; n = rb_next(n)) {
                struct ion_client *client = rb_entry(n, struct ion_client,
                                                     node);
@@ -1433,6 +1473,8 @@ static int ion_debug_heap_show(struct seq_file *s, void *unused)
                                   client->pid, size);
                }
        }
+       mutex_unlock(&debugfs_mutex);
+
        seq_puts(s, "----------------------------------------------------\n");
        seq_puts(s, "orphaned allocations (info is from last known client):\n");
        mutex_lock(&dev->buffer_lock);
@@ -1617,6 +1659,8 @@ debugfs_done:
        init_rwsem(&idev->lock);
        plist_head_init(&idev->heaps);
        idev->clients = RB_ROOT;
+       ion_root_client = &idev->clients;
+       mutex_init(&debugfs_mutex);
        return idev;
 }
 EXPORT_SYMBOL(ion_device_create);