Am 2016-08-08 23:51, schrieb Adam Lackorzynski:
On Mon Aug 08, 2016 at 12:32:02 +0200, ba_f wrote:
Am 2016-08-05 15:08, schrieb Matthias Lange:
Hi,
On 08/04/2016 03:05 PM, ba_f wrote:
But, is it also possible to do some configuration during run-time i.e. dynamic reconfiguration? Here are two examples I can think of:
Well, it depends ...
- IPC-Channels: Instead of defining Server and its Clients in conf.cfg
statically, is it possible to create IPC-Channel during run-time? Let's say, I have a L4re-App in conf.cfg defined as IPC-Server but, no Clients, yet. Now, may any L4re-App create a IPC-Channel by itself and such link to that IPC-Server?
The answer is 'Yes.' and 'No'. The answer to the first question is that this is exactly what ned is doing. Ned creates an IPC gate object and maps it into the tasks as specified in the provided Lua configuration.
The second is not possible for multiple reasons. The first one is, that the server side already needs the IPC gate object to bind its server loop to. Another task has no means to "lookup" the existing IPC gate object. In fact that's the idea behind a capability system.
So, what you are saying is this: In fact, Ned maps the IPC-Channels at run-time but practically, one has to configure all IPC-Channels possible in Lua.cfg, statically. An ordinary L4Re-App is not able to link to an IPC-Server App if this channel hasn't been configured in Lua.cfg, right?
Yes.
In this case, the L4Re-App also cannot manipulate Ned or something at run-time to create an IPC-Channel, afterwards.
It cannot because Ned does not have an interface to do that. Generally, if two tasks want to communicate, both need to have a cap on the ipc-channel. As those two cannot communicate (yet), there has to be a third component (with appropriate access to the two that want to communicate) to establish the connection.
Adam
Ok, I see it's not possible. But, maybe I can take the chance for a deeper understanding.
This is how I understand things, now. Please, correct me if I'm wrong:
1.) Moe starts first, followed by Ned. 2.) Ned parses lua.cfg and, on 'new_channel()' it creates a new IPC-Gate with l4_msgtag_t l4_factory_create_gate( l4_cap_idx_t factory, l4_cap_idx_t target_cap, l4_cap_idx_t thread_cap, l4_umword_t label). 3.) The IPC-Gate is a Kernel-Object and thus stored into the Kernel. (Does Moe help here?) 'thread_cap' is stored/pushed into the servers capability table and 'target_cap' is for the client task, aren't they? 4.) With l4re_env_get_cap() client & server look for a matching capability in their own cap-tables.
If I got it right, any Task can create an IPC-Gate at run-time and thus create child tasks with ipc-server or ipc-client capabilities, don't they?
Thanks,
ba_f