Re: [PATCH] PM: runtime: fix recursive locking warning of lockdep from rpm_resume

Alan Stern
2010-10-22T14:25:24Z

On Fri, 22 Oct 2010 tom.leiming@gmail.com wrote:

> From: Ming Lei <tom.leiming@gmail.com>
>
> For device with no_callbacks flag set, its power lock and its parent's
> power lock may be held nestedly in rpm_resume, so we should take
> spin_lock_nested(lock, SINGLE_DEPTH_NESTING) to acquire parent power lock
> to avoid lockdep warning.
>
> Signed-off-by: Ming Lei <tom.leiming@gmail.com>
> ---
> drivers/base/power/runtime.c | 2 +-
> 1 files changed, 1 insertions(+), 1 deletions(-)
>
> diff --git a/drivers/base/power/runtime.c b/drivers/base/power/runtime.c
> index 1dd8676..126ca49 100644
> --- a/drivers/base/power/runtime.c
> +++ b/drivers/base/power/runtime.c
> @@ -503,7 +503,7 @@ static int rpm_resume(struct device *dev, int rpmflags)
> * the resume will actually succeed.
> */
> if (dev->power.no_callbacks && !parent && dev->parent) {
> - spin_lock(&dev->parent->power.lock);
> + spin_lock_nested(&dev->parent->power.lock, SINGLE_DEPTH_NESTING);
> if (dev->parent->power.disable_depth > 0
> || dev->parent->power.ignore_children
> || dev->parent->power.runtime_status == RPM_ACTIVE) {

Quite correct; I don't know why this didn't show up during my testing.

Acked-by: Alan Stern <stern@rowland.harvard.edu>