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This commit is contained in:
Niko Matsakis 2019-07-05 06:05:18 -04:00
parent 346ce6bc16
commit d4f7e4b2b4
1 changed files with 9 additions and 2 deletions
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11
src/input.rs
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@ -144,14 +144,21 @@ where
durability durability
); );
// The value is changing, so even if we are setting this to a // The value is changing, so we need a new revision (*). We also
// constant, we still need a new revision. // need to update the 'last changed' revision by invoking
// `guard.mark_durability_as_changed`.
// //
// CAREFUL: This will block until the global revision lock can // CAREFUL: This will block until the global revision lock can
// be acquired. If there are still queries executing, they may // be acquired. If there are still queries executing, they may
// need to read from this input. Therefore, we wait to acquire // need to read from this input. Therefore, we wait to acquire
// the lock on `map` until we also hold the global query write // the lock on `map` until we also hold the global query write
// lock. // lock.
//
// (*) Technically, since you can't presently access an input
// for a non-existent key, and you can't enumerate the set of
// keys, we only need a new revision if the key used to
// exist. But we may add such methods in the future and this
// case doesn't generally seem worth optimizing for.
db.salsa_runtime().with_incremented_revision(|guard| { db.salsa_runtime().with_incremented_revision(|guard| {
let mut slots = self.slots.write(); let mut slots = self.slots.write();