[PATCH v2 00/12] Bluetooth: Move LE scan changes behind req_workqueue

[Johan Hedberg <johan.hedberg@gmail.com>]

Hi,

v2: updated version with feedback for 01/12 and 02/12 taken into
account.

>From the original cover letter:

The current bluetooth-next tree is not able to reliably and in a
race-free manner handle updates to the LE scan state. This results in
the kernel ending up out of sync with the actual LE scan state and
starts sending incorrect scan state HCI commands, often resulting in
"not allowed" HCI responses.

This is an initial set of patches to try solve the issue. I've tried to
retain as much as possible of the original logic so that it's easier to
see that nothing should get broken. Because of this, there are still
many simplifications and cleanups that can be done. However, since I've
already got 12 patches lined up I wanted to get them sent, reviewed and
merged. After that I can concentrate on the cleanups and I'll also be
looking into moving the adverising state changes to hci_request.c as
well.

The general solution that this set takes to solve the synchronization
issues with the LE scan state, is to move all of it behind the
hdev->req_workqueue and perform the actions synchronously. The main tool
I've used for this is the hci_req_sync() API which allows taking
existing asynchronous HCI request helpers and using them to perform the
same commands synchronously (by passing the helper as the callback to
hci_req_sync).

Since only one work callback is active at a time we get an easy way to
avoid races between the changes. All of the new synchronous code can be
found in hci_request.c which seemed like an appropriate place for it.

I've done a fair amount of testing with the patches, including
mgmt-tester, l2cap-tester and various bluetoothd tests (both with
controllers supporting simultaneous Inquiry+LE scan as well as those not
supporting it). However, because of the size of the changes it's
perfectly possible that I've missed or broken something, so it'd be good
if others could give the set a spin before merging it.

Johan

----------------------------------------------------------------
Johan Hedberg (12):
      Bluetooth: Add stubs for synchronous HCI request functionality
      Bluetooth: Run all background scan updates through req_workqueue
      Bluetooth: Don't wait for HCI in Add/Remove Device
      Bluetooth: Add HCI status return parameter to hci_req_sync()
      Bluetooth: Use req_workqueue for explicit connect requests
      Bluetooth: Use req_workqueue for background scanning when powering on
      Bluetooth: Make __hci_update_background_scan private to hci_request.c
      Bluetooth: Move LE scan disable/restart behind req_workqueue
      Bluetooth: Add discovery type validity helper
      Bluetooth: Add error return value to hci_req_sync callback
      Bluetooth: Move Start Discovery to req_workqueue
      Bluetooth: Move Stop Discovery to req_workqueue

 include/net/bluetooth/hci.h      |   3 +-
 include/net/bluetooth/hci_core.h |  10 +-
 net/bluetooth/hci_conn.c         |  39 +--
 net/bluetooth/hci_core.c         | 243 ++++-------------
 net/bluetooth/hci_request.c      | 537 +++++++++++++++++++++++++++++++++++---
 net/bluetooth/hci_request.h      |  26 +-
 net/bluetooth/mgmt.c             | 503 +++++++----------------------------
 7 files changed, 684 insertions(+), 677 deletions(-)