On Mon, 2017-08-28 at 10:05 +0200, Greg Kroah-Hartman wrote:
> 4.4-stable review patch. If anyone has any objections, please let me know.
>
> ------------------
>
> From: Jeffy Chen <jeffy.chen@xxxxxxxxxxxxxx>
>
> commit 5da8e47d849d3d37b14129f038782a095b9ad049 upstream.
>
> It looks like hidp_session_thread has same pattern as the issue reported in
> old rfcomm:
>
> while (1) {
> set_current_state(TASK_INTERRUPTIBLE);
> if (condition)
> break;
> // may call might_sleep here
> schedule();
> }
> __set_current_state(TASK_RUNNING);
>
> Which fixed at:
> dfb2fae Bluetooth: Fix nested sleeps
>
> So let's fix it at the same way, also follow the suggestion of:
> https://lwn.net/Articles/628628/
>
> Signed-off-by: Jeffy Chen <jeffy.chen@xxxxxxxxxxxxxx>
> Tested-by: AL Yu-Chen Cho <acho@xxxxxxxx>
> Tested-by: Rohit Vaswani <rvaswani@xxxxxxxxxx>
> Signed-off-by: Marcel Holtmann <marcel@xxxxxxxxxxxx>
> Cc: Jiri Slaby <jslaby@xxxxxxx>
> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
>
> ---
> net/bluetooth/hidp/core.c | 33 ++++++++++++++++++++++-----------
> 1 file changed, 22 insertions(+), 11 deletions(-)
>
> --- a/net/bluetooth/hidp/core.c
> +++ b/net/bluetooth/hidp/core.c
[...]
> + /* Ensure session->terminate is updated */
> + smp_mb__before_atomic();
> if (atomic_read(&session->terminate))
> break;
[...]
smp_mb__before_atomic() is only meant to avoid adding a redundant
barrier next to an atomic RMW operation if it already includes one
(which is arch-dependent). atomic_read() is not an RMW operation and
never includes a barrier, so it needs an smp_mb() before it.
Ben.
--
Ben Hutchings
Software Developer, Codethink Ltd.