Improve non-reentrance wording in Explainer.md

Author: lukewagner

design/mvp/Explainer.md

@@ -1721,11 +1721,12 @@ If `cancellable` is set, `waitable-set.wait` may return `task-cancelled`
 propagated once received.
 
 If `waitable-set.wait` is called from a synchronous- or `async callback`-lifted
-export, no other synchronous- or `async callback`-lifted threads can start or
-progress in the current component instance (ensuring non-reentrance of the core
-wasm code) until it returns. However, explicitly-created threads and
-non-`callback` `async`-lifted ("stackful async") exports may start or progress
-at any time.
+export, no other threads that were implicitly created by a separate
+synchronous- or `async callback`-lifted export call can start or progress in
+the current component instance until `waitable-set.wait` returns (thereby
+ensuring non-reentrance of the core wasm code). However, explicitly-created
+threads and threads implicitly created by non-`callback` `async`-lifted
+("stackful async") exports may start or progress at any time.
 
 A `subtask` event notifies the supertask that its subtask is now in the given
 state (the meanings of which are described by the [concurrency explainer]).
@@ -1762,11 +1763,12 @@ If `cancellable` is set, `waitable-set.poll` may return `task-cancelled`
 propagated once received.
 
 If `waitable-set.poll` is called from a synchronous- or `async callback`-lifted
-export, no other synchronous- or `async callback`-lifted threads can start or
-progress in the current component instance (ensuring non-reentrance of the core
-wasm code) until it returns. However, explicitly-created threads and
-non-`callback` `async`-lifted ("stackful async") exports may start or progress
-at any time.
+export, no other threads that were implicitly created by a separate
+synchronous- or `async callback`-lifted export call can start or progress in
+the current component instance until `waitable-set.poll` returns (thereby
+ensuring non-reentrance of the core wasm code). However, explicitly-created
+threads and threads implicitly created by non-`callback` `async`-lifted
+("stackful async") exports may start or progress at any time.
 
 The Canonical ABI of `waitable-set.poll` is the same as `waitable-set.wait`
 (with the `none` case indicated by returning `0`).
@@ -2103,11 +2105,12 @@ if `cancellable` was set, [cancellation], `thread.switch-to` will return,
 indicating what happened.
 
 If `thread.switch-to` is called from a synchronous- or `async callback`-lifted
-export, no other synchronous- or `async callback`-lifted threads can start or
-progress in the current component instance (ensuring non-reentrance of the core
-wasm code) until it returns. However, explicitly-created threads and
-non-`callback` `async`-lifted ("stackful async") exports may start or progress
-at any time.
+export, no other threads that were implicitly created by a separate
+synchronous- or `async callback`-lifted export call can start or progress in
+the current component instance until `thread.switch-to` returns (thereby
+ensuring non-reentrance of the core wasm code). However, explicitly-created
+threads and threads implicitly created by non-`callback` `async`-lifted
+("stackful async") exports may start or progress at any time.
 
 For details, see [`canon_thread_switch_to`] in the Canonical ABI explainer.
 
@@ -2126,11 +2129,12 @@ the current thread is resumed by some other thread or, if `cancellable` was
 set, [cancellation], `thread.suspend` will return, indicating what happened.
 
 If `thread.suspend` is called from a synchronous- or `async callback`-lifted
-export, no other synchronous- or `async callback`-lifted threads can start or
-progress in the current component instance (ensuring non-reentrance of the core
-wasm code) until it returns. However, explicitly-created threads and
-non-`callback` `async`-lifted ("stackful async") exports may start or progress
-at any time.
+export, no other threads that were implicitly created by a separate
+synchronous- or `async callback`-lifted export call can start or progress in
+the current component instance until `thread.suspend` returns (thereby
+ensuring non-reentrance of the core wasm code). However, explicitly-created
+threads and threads implicitly created by non-`callback` `async`-lifted
+("stackful async") exports may start or progress at any time.
 
 For details, see [`canon_thread_suspend`] in the Canonical ABI explainer.
 
@@ -2163,11 +2167,12 @@ due to runtime scheduling or, if `cancellable` was set, [cancellation],
 `thread.yield-to` will return, indicating what happened.
 
 If `thread.yield-to` is called from a synchronous- or `async callback`-lifted
-export, no other synchronous- or `async callback`-lifted threads can start or
-progress in the current component instance (ensuring non-reentrance of the core
-wasm code) until it returns. However, explicitly-created threads and
-non-`callback` `async`-lifted ("stackful async") exports may start or progress
-at any time.
+export, no other threads that were implicitly created by a separate
+synchronous- or `async callback`-lifted export call can start or progress in
+the current component instance until `thread.yield-to` returns (thereby
+ensuring non-reentrance of the core wasm code). However, explicitly-created
+threads and threads implicitly created by non-`callback` `async`-lifted
+("stackful async") exports may start or progress at any time.
 
 For details, see [waiting] in the concurrency explainer and
 [`canon_thread_yield_to`] in the Canonical ABI explainer.
@@ -2187,11 +2192,12 @@ resumed either due to runtime scheduling or, if `cancellable` was set,
 [cancellation], `thread.yield` will return, indicating what happened.
 
 If `thread.yield` is called from a synchronous- or `async callback`-lifted
-export, no other synchronous- or `async callback`-lifted threads can start or
-progress in the current component instance (ensuring non-reentrance of the core
-wasm code) until it returns. However, explicitly-created threads and
-non-`callback` `async`-lifted ("stackful async") exports may start or progress
-at any time.
+export, no other threads that were implicitly created by a separate
+synchronous- or `async callback`-lifted export call can start or progress in
+the current component instance until `thread.yield` returns (thereby
+ensuring non-reentrance of the core wasm code). However, explicitly-created
+threads and threads implicitly created by non-`callback` `async`-lifted
+("stackful async") exports may start or progress at any time.
 
 For details, see [waiting] in the concurrency explainer and
 [`canon_thread_yield`] in the Canonical ABI explainer.