Re: BlueZ/mesh: RX not working after daemon restart (with workaround)

["Stotland, Inga" <inga.stotland@intel.com>]

Hi Aurelien,

On Sun, 2019-11-10 at 22:39 +0100, Aurelien Jarno wrote:
> Hi,
> 
> On 2019-11-10 13:59, Steve Brown wrote:
> > On Sun, 2019-11-10 at 21:08 +0100, Aurelien Jarno wrote:
> > > Hi all,
> > > 
> > > On my system (Raspberry PI 3), the RX path doesn't work anymore
> > > following a restart of the bluetooth-meshd daemon. I have tracked
> > > down
> > > that to the fact that the receive callbacks are setup before the HCI
> > > is
> > > fully initialized. Said otherwise, BT_HCI_CMD_LE_SET_SCAN_PARAMETERS
> > > is
> > > called before BT_HCI_CMD_RESET and the callback calling
> > > BT_HCI_CMD_LE_SET_SCAN_ENABLE is not called. This timing dependent
> > > and
> > > probably not reproducible on all hardware.
> > > 
> > > I have workarounded the issue by adding a small delay between the HCI
> > > initialization and the call to node_attach_io_all():
> > > 
> > > diff --git a/mesh/mesh.c b/mesh/mesh.c
> > > index 9b2b2073b..1c06060f9 100644
> > > --- a/mesh/mesh.c
> > > +++ b/mesh/mesh.c
> > > @@ -167,6 +167,10 @@ bool mesh_init(const char *config_dir, enum
> > > mesh_io_type type, void *opts)
> > >  	mesh_io_get_caps(mesh.io, &caps);
> > >  	mesh.max_filters = caps.max_num_filters;
> > >  
> > > +	for (int i = 0 ; i < 100 ; i++) {
> > > +		l_main_iterate(10);
> > > +	}
> > > +
> > >  	node_attach_io_all(mesh.io);
> > >  
> > >  	return true;
> > > 
> > > I guess there is a better way to do that by waiting for the HCI to be
> > > fully initialized before calling node_attach_io_all() or by using a
> > > callback instead. However I do not know the codebase good enough to
> > > fix
> > > that properly.
> > > 
> > > Aurelien
> > > 
> > I've experienced something similar on my rpi3. I found that on restart,
> > discover-unprovisioned stopped working.
> 
> In my case I also observe the same.
> 
> > In my case, it appears that meshd assumes that if there are existing
> > nodes, scanning has been enabled. Thus, calls from mesh-cfgclient to
> > discover additional unprovisioned nodes do not need another hci scan
> > enable at mesh/mesh-io-generic.c:736.
> > 
> > If meshd is restarted with preexisting nodes, scanning is still assumed
> > to already be enabled, but it's not. This breaks discover-unprovisioned 
> > for me.
> 
> Yes, I think this is exactly my problem. If there are existing nodes,
> recv_register is called before the HCI is configured and pvt->rx_regs is
> filled at mesh/mesh-io-generic.c:738. This means that later scanning is
> assumed to be enabled. However the call to bt_hci_send with
> BT_HCI_CMD_LE_SET_SCAN_PARAMETERS fails as the HCI is not yet
> initialized and the callback set_recv_scan_enable() supposed to enable
> scanning is not called.
> 
> So when loading a node, scanning is assumed to be enabled, but it is
> not practice.
> 
> I believe my workaround should work on your system (maybe after
> adjusting the number of iterations of the loop).
> 
> Aurelien
>  

Thanks for the analysis. I think we should switch to callback approach,
i.e. initialize io first and register the RX on the successful init
callback.

Best regards,
Inga