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Update some comments in slot.rs

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Signed-off-by: Michal Terepeta <michal.terepeta@gmail.com>
This commit is contained in:
Michal Terepeta 2020-01-12 19:26:21 +01:00 committed by Aleksey Kladov
parent 37a3650aef
commit 97ed750a9d
1 changed files with 15 additions and 29 deletions
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44
src/derived/slot.rs
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@ -314,26 +314,17 @@ where
Ok(new_value)
}
/// Helper for `read`:
/// Helper for `read` that does a shallow check (not recursive) if we have an up-to-date value.
///
/// Invoked with the guard `map` of some lock on `self.map` (read
/// or write) as well as details about the key to look up. Looks
/// in the map to see if we have an up-to-date value or a
/// cycle. Returns a suitable `ProbeState`:
/// Invoked with the guard `state` corresponding to the `QueryState` of some `Slot` (the guard
/// can be either read or write). Returns a suitable `ProbeState`:
///
/// - `ProbeState::UpToDate(r)` if the table has an up-to-date
/// value (or we blocked on another thread that produced such a value).
/// - `ProbeState::CycleDetected` if this thread is (directly or
/// indirectly) already computing this value.
/// - `ProbeState::BlockedOnOtherThread` if some other thread
/// (which does not depend on us) was already computing this
/// value; caller should re-acquire the lock and try again.
/// - `ProbeState::StaleOrAbsent` if either (a) there is no memo
/// for this key, (b) the memo has no value; or (c) the memo
/// has not been verified at the current revision.
/// - `ProbeState::UpToDate(r)` if the table has an up-to-date value (or we blocked on another
/// thread that produced such a value).
/// - `ProbeState::StaleOrAbsent(g)` if either (a) there is no memo for this key, (b) the memo
/// has no value; or (c) the memo has not been verified at the current revision.
///
/// Note that in all cases **except** for `StaleOrAbsent`, the lock on
/// `map` will have been released.
/// Note that in case `ProbeState::UpToDate`, the lock will have been released.
fn probe<StateGuard>(
&self,
db: &DB,
@ -351,8 +342,7 @@ where
let other_id = *id;
return match self.register_with_in_progress_thread(db, runtime, other_id, waiting) {
Ok(rx) => {
// Release our lock on `self.map`, so other thread
// can complete.
// Release our lock on `self.state`, so other thread can complete.
std::mem::drop(state);
db.salsa_event(|| Event {
@ -895,8 +885,7 @@ where
);
match self.register_with_in_progress_thread(db, runtime, other_id, waiting) {
Ok(rx) => {
// Release our lock on `self.map`, so other thread
// can complete.
// Release our lock on `self.state`, so other thread can complete.
std::mem::drop(state);
let result = rx.recv().unwrap_or_else(|_| db.on_propagated_panic());
@ -972,11 +961,9 @@ where
};
}
// We have a **tracked set of inputs** that need to be validated.
let inputs = inputs.clone();
// We have a **tracked set of inputs**
// (found in `database_keys`) that need to
// be validated.
// We'll need to update the state anyway (see below), so release the read-lock.
std::mem::drop(state);
// Iterate the inputs and see if any have maybe changed.
@ -992,10 +979,9 @@ where
// Either way, we have to update our entry.
//
// Keep in mind, though, we only acquired a read lock so a lot
// could have happened in the interim. =) Therefore, we have
// to probe the current state of `key` and in some cases we
// ought to do nothing.
// Keep in mind, though, that we released the lock before checking the ipnuts and a lot
// could have happened in the interim. =) Therefore, we have to probe the current
// `self.state` again and in some cases we ought to do nothing.
{
let mut state = self.state.write();
match &mut *state {