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SubjectRe: [PATCH linux-next] mm: fix rcu-lock/unlock balance in vm_is_stack()
On Wed, 21 Mar 2012 00:54:55 +0400
Konstantin Khlebnikov <khlebnikov@openvz.org> wrote:

> Fix bug introduced in "procfs: mark thread stack correctly in proc/<pid>/maps"
> (patch in mm/linux-next)
>
> Signed-off-by: Konstantin Khlebnikov <khlebnikov@openvz.org>
> ---
> mm/memory.c | 5 ++---
> 1 files changed, 2 insertions(+), 3 deletions(-)
>
> diff --git a/mm/memory.c b/mm/memory.c
> index ee85fc4..cc08b86 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -3932,13 +3932,12 @@ pid_t vm_is_stack(struct task_struct *task,
> while_each_thread(task, t) {
> if (vm_is_stack_for_task(t, vma)) {
> ret = t->pid;
> - goto done;
> + break;
> }
> }
> + rcu_read_unlock();
> }
>
> -done:
> - rcu_read_unlock();
> return ret;
> }
>

Appears to have been fixed in v3:

pid_t vm_is_stack(struct task_struct *task,
struct vm_area_struct *vma, int in_group)
{
pid_t ret = 0;

if (vm_is_stack_for_task(task, vma))
return task->pid;

if (in_group) {
struct task_struct *t;
rcu_read_lock();
if (!pid_alive(task))
goto done;

t = task;
do {
if (vm_is_stack_for_task(t, vma)) {
ret = t->pid;
goto done;
}
} while_each_thread(task, t);
done:
rcu_read_unlock();
}

return ret;
}

I'm working on getting a -next update sent to Stephen today.


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