Commits on Nov 3, 2022

1. rt: unify entering a runtime with Handle::enter …

   This is a frist step towards unifying the concepts of "entering a
   runtime" and setting `Handle::current`.
   
   Previously, these two operation were performed separately at each call
   site (runtime block_on, ...). This is error prone and also requires
   multiple accesses to the thread-local variable. Additionally, "entering
   the runtime" conflated the concept of entering a blocking region. For
   example, calling `mpsc::Receiver::recv_blocking` performed the "enter
   the runtime" step. This was done to prevent blocking a runtime as the
   operation will panic when called from an existing runtime.
   
   To untangle these concepts, the patch splits out each logical operation
   into its own call. In total, there are three "enter" operations:
   
   * `set_current_handle`
   * `enter_runtime`
   * `enter_blocking_region`
   
   There are some behavior changes with each of these functions, but they
   should not translate to public behavior changes. The most signifcant is
   `enter_blocking_region` does not change the value of the thread-local
   variable, which means the function can be re-entered. Since
   `enter_blocking_region` is an internal-only function and we do not
   actually re-enter, this has no public facing impact.
   
   Because `enter_runtime` takes a `&Handle` in order to combine the
   `set_current_handle` operation with entering a runtime, the patch
   exposes an annoyance with the current `scheduler::Handle` struct layout.
   A new instance of `scheduler::Handle` must be constructed at each call
   to `enter_runtime`. We can explore cleaning this up later.
   
   This patch also does not combine the "entered runtime" thread-local
   variable with the "context" thread-local variable. To keep the patch
   smaller, this has been punted to a follow up change.

   

   carllerche committed Nov 3, 2022
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2. Merge remote-tracking branch 'origin/master' into cleanup-enter

   

   carllerche committed Nov 3, 2022
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   296b8bc View commit details

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