Hello all,
I am about to merge a PR
(https://github.com/apache/mynewt-core/pull/1075) which eliminates the
need to explicitly call `conf_load()`. Nothing bad will happen if your
app continues to call `conf_load()`, but the call can be safely removed
after the PR is merged.
Background-
The `sys/config` package is used for persisting data across reboots. To
restore all the persisted data from flash, an app had to manually call
`conf_load()`, typically from `main()`. It would be preferable for the
data to get loaded automatically during system initialization, but
this is not possible; the underlying storage containing the config data
is not ready for use until the application explicitly initializes it in
`main()`. Typically, config data is stored in a flash circular buffer
(fcb), something which sysinit and syscfg know nothing about, and which
must be manually initialzed by the app. Thus, `conf_load()` during
sysinit would fail.
The PR referenced above causes `conf_load()` to be called automatically,
but it delays the call until the default event queue begins being
processed. Typically, the default event queue is processed in an
infinite loop at the end of `main()`, so delaying the call to
`conf_load()` to this point gives `main()` the opportunity to initialize
FCBs and other storage first.
Issue-
Packages may attempt to access persisted data before `conf_load()` has
been called. This issue has always existed, but the referenced PR
exacerbates it. This issue can arise in a number of ways:
(1) Package tries to use persisted data during sysinit.
(2) High priority task tries to use persisted data as soon as it starts
running.
(3) Package that runs in the default task tries to use persisted data
immediately after sysinit completes.
(1) and (2) were always an issue. (3) is a new issue that arises if an
app takes advantage of the automatic call to `conf_load()`. If your app
uses a package which tries to use persisted data immediately on startup,
then you may want to continue calling `conf_load()` from `main()`.
Thanks,
Chris
