Hi, All
Recently I met one race condition related to debugfs.
Take an example from ion.c in kernel3.14:
static int ion_debug_client_open(struct inode *inode, struct file *file)
{
return single_open(file, ion_debug_client_show, inode->i_private);
}
static const struct file_operations debug_client_fops = {
.open = ion_debug_client_open,
.read = seq_read,
.llseek = seq_lseek,
.release = single_release,
};
client->debug_root = debugfs_create_file(client->display_name, 0664,
dev->clients_debug_root,
client, &debug_client_fops);
I find during I read the debugfs node, driver can do
debugfs_remove_recursive(dentry);
Is it expected?
In this case, when do the seq_file read, it grabs the seq_file->lock;
While in debugfs_remove_recursive(), it graps "parent->d_inode->i_mutex".
So there seems no protection between the ion_debug_client_show() and
debugfs_remove_recursive().
Please let me know if I didn't describe the issue clear.
Would you help to comment if there's method to avoid such issue?
Best Regards.
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