Hi Johan, > v2 has minor fixes to a code comment in patch 1/2 and the commit message > of patch 2/2. > > From the original cover letter: > > I've spent the last few days fighting with all sorts of lockdep warnings > in the Bluetooth subsystem. A lot of them come from the fact that we > have cross-channel access for L2CAP channels. This ends up looking > suspicious to lockdep unless we help out a bit by adding nesting level > annotations. > > It seems like we need at least three distinct nesting levels: SMP > channels, "normal" channels, and parent/listening channels. This is > because the parent channel lock may be held while also taking the lock > of child channels, and the SMP channel may be accessed while holding the > lock of any other channel (e.g. to request security level elevation). > > We could in theory identify the type of channel in question implicitly > by inspecting the channel in the l2cap_chan_lock function, however this > is problematic since accessing channel data would usually already > require holding the channel lock (not to mention that the logic for > selecting the needed nesting level wouldn't be completely trivial). > > A simpler (imo) solution that I've gone for is to introduce a new > "atomic_t nesting" channel member which contains the necessary nesting > level and is set as soon as the level is known (i.e. initialized to > "normal" upon channel creation or set to one of the two other levels > when creating the SMP chan in smp.c or when setting chan->state to > BT_LISTEN). > > The second patch contains a long needed fix for l2cap_sock_teardown_cb > which only got a half-fix earlier this week (also from me) for its > locking. This function gets called for all types of channels so it can't > have a hard-coded nesting level for the socket lock. Instead I've opted > for the socket lock inheriting the chan level and then also using that > for the two other places calling lock_sock_nested() to be consistent. > > Johan > > ---------------------------------------------------------------- > Johan Hedberg (2): > Bluetooth: Use proper nesting annotation for l2cap_chan lock > Bluetooth: Fix L2CAP socket lock nesting level > > include/net/bluetooth/l2cap.h | 15 ++++++++++++++- > net/bluetooth/l2cap_sock.c | 22 +++++++++++++++++++--- > net/bluetooth/smp.c | 10 ++++++++++ > 3 files changed, 43 insertions(+), 4 deletions(-) both patches have been applied to bluetooth-next tree. Regards Marcel -- To unsubscribe from this list: send the line "unsubscribe linux-bluetooth" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
