Installing the out-of-band stage

Before you can direct the incoming interrupt flow to out-of-band handlers, you need to install the out-of-band interrupt stage. Conversely, you need to remove the out-of-band stage from the interrupt pipeline when you are done with receiving out-of-band events.


int enable_oob_stage(const char *name)

  • name

    A symbolic name describing the high priority interrupt stage which is being installed. This information is merely used in kernel messages, so it should be short but descriptive enough. For instance, the EVL core installs the “EVL” stage.

  • This call enables the out-of-band stage context in the interrupt pipeline, which in turn allows an autonomous core to install out-of-band handlers for interrupts. It returns zero on success, or a negated error code if something went wrong:

    -EBUSY The out-of-band stage is already enabled.


    void disable_oob_stage(void)

    This call disables the out-of-band stage context in the interrupt pipeline. From that point, the interrupt flow is exclusively directed to the in-band stage.

    This call does NOT perform any serialization with ongoing interrupt handling on remote CPUs whatsoever. The autonomous core must synchronize with remote CPUs before calling disable_oob_stage() to prevent them from running out-of-band handlers while the out-of-band stage is being dismantled. This is particularly important if these handlers belong to a dynamically loaded module which might be unloaded right after disable_oob_stage() returns. In that case, you certainly don’t want the .text section containing interrupt handlers to vanish while they are still running.