Hi George, OK, thanks for confirming. It looks like the same issue would occur for GET requests as well - if `oc_do_get` is interrupted (before the request is dispatched, and another thread begins building a new root object).
We'll make sure that our application logic protects against this. Thanks! On Fri, Jun 5, 2020 at 2:18 AM Nash, George <[email protected]> wrote: > If you have a situation that two threads may call oc_init_post then you > must prevent both threads calling oc_init_post at the same time. You must > add a mutex or some other similar guard before calling oc_init_post and > then you can release it after calling oc_do_post. The same is true for > oc_init_put and oc_do_put. > > > > George Nash > > > > *From:* [email protected] <[email protected]> *On > Behalf Of *[email protected] > *Sent:* Wednesday, June 3, 2020 11:00 PM > *To:* [email protected] > *Subject:* [dev] Protecting against concurrent requests > > > > I'm particularly interested in how the following scenario is prevented: > > 1. Code from one thread ("A") in the application calls > `prepare_coap_request` (which in turn, calls `oc_rep_new`, resetting the > current CBOR encoder state). For example, this might happen by someone > calling `oc_init_post`. > 2. Thread "A" sees a 'success' from `oc_init_post`, and calls > `oc_rep_begin_root_object` and begins building a request body > 3. Thread "A" is interrupted by higher priority thread "B" which calls > `oc_init_post`. > 4. Thread "B" completes and sends request > 5. Control is returned to thread "A", which continues trying to build a > request body, but the data is now meaningless (since the state of > `g_encoder` and `root_map` in `oc_rep.h` have been modified > > Looking over the example apps, most seem to provide protection against > this by ensuring that requests are not created in interrupts, and/or > requests are sent via a menu driven interface. Are there further safeguards > against this concurrency issue, is it actually a nonissue, or am I > misunderstanding something here? > > > -- Joshua Milburn, P.E. | Senior Embedded Systems Engineer +1 (724) 612 7788 | Skype: jjmilburn Subscribe <https://bit.ly/2YvJWMa> to Angaza’s newsletter Twitter <https://bit.ly/3aWwLGG> | Facebook <https://bit.ly/3bXHouj> | LinkedIn <https://bit.ly/3d4MCEB> | YouTube <https://bit.ly/3d7rtd7> <https://bit.ly/2VTrTOh> -=-=-=-=-=-=-=-=-=-=-=- Groups.io Links: You receive all messages sent to this group. View/Reply Online (#10389): https://iotivity.groups.io/g/iotivity-dev/message/10389 Mute This Topic: https://groups.io/mt/74666318/21656 Group Owner: [email protected] Unsubscribe: https://iotivity.groups.io/g/iotivity-dev/unsub [[email protected]] -=-=-=-=-=-=-=-=-=-=-=-
