Re: + syscalls-x86-add-__nr_kcmp-syscall-v8.patch added to -mm tree

Cyrill Gorcunov
2012-02-15T18:32:10Z

On Wed, Feb 15, 2012 at 07:10:08PM +0400, Cyrill Gorcunov wrote:
> On Wed, Feb 15, 2012 at 03:36:06PM +0100, Oleg Nesterov wrote:
> >
> > task->files can be NULL, we can race with exit_files().
>
> So I need to call get_files_struct. Thanks Oleg!
>

Something like below I think, right? (it seems this
patc doesn't hit lenux-next yet, so here is interdiff
output)

Cyrill
---
diff -u linux-2.6.git/kernel/kcmp.c linux-2.6.git/kernel/kcmp.c
--- linux-2.6.git/kernel/kcmp.c
+++ linux-2.6.git/kernel/kcmp.c
@@ -44,16 +44,25 @@
static struct file *
get_file_raw_ptr(struct task_struct *task, unsigned int idx)
{
+ struct files_struct *files;
struct fdtable *fdt;
struct file *file;

- spin_lock(&task->files->file_lock);
- fdt = files_fdtable(task->files);
+ files = get_files_struct(task);
+ if (!files)
+ return NULL;
+
+ rcu_read_lock();
+
+ fdt = files_fdtable(files);
if (idx < fdt->max_fds)
file = fdt->fd[idx];
else
file = NULL;
- spin_unlock(&task->files->file_lock);
+
+ rcu_read_unlock();
+
+ put_files_struct(files);

return file;
}