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Merge pull request #75 from nikomatsakis/issue-70

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remove use of upgradable reads from derived queries
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Niko Matsakis 2018-12-28 10:20:36 -05:00 committed by GitHub
commit dd1b6edc01
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2 changed files with 15 additions and 19 deletions
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1
src/debug.rs
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@ -3,7 +3,6 @@
use crate::plumbing;
use crate::plumbing::QueryStorageOps;
use crate::Database;
use crate::Query;
use crate::QueryTable;
use std::iter::FromIterator;

33
src/derived.rs
View file

@ -13,7 +13,7 @@ use crate::runtime::StampedValue;
use crate::{Database, Event, EventKind, SweepStrategy};
use log::{debug, info};
use parking_lot::Mutex;
use parking_lot::{RwLock, RwLockUpgradableReadGuard};
use parking_lot::RwLock;
use rustc_hash::FxHashMap;
use smallvec::SmallVec;
use std::marker::PhantomData;
@ -284,24 +284,21 @@ where
// Check with an upgradable read to see if there is a value
// already. (This permits other readers but prevents anyone
// else from running `read_upgrade` at the same time.)
let mut old_memo = match self.probe(
db,
self.map.upgradable_read(),
runtime,
revision_now,
descriptor,
key,
) {
ProbeState::UpToDate(v) => return v,
ProbeState::StaleOrAbsent(map) => {
let mut map = RwLockUpgradableReadGuard::upgrade(map);
match map.insert(key.clone(), QueryState::in_progress(runtime.id())) {
Some(QueryState::Memoized(old_memo)) => Some(old_memo),
Some(QueryState::InProgress { .. }) => unreachable!(),
None => None,
//
// FIXME(Amanieu/parking_lot#101) -- we are using a write-lock
// and not an upgradable read here because upgradable reads
// can sometimes encounter deadlocks.
let mut old_memo =
match self.probe(db, self.map.write(), runtime, revision_now, descriptor, key) {
ProbeState::UpToDate(v) => return v,
ProbeState::StaleOrAbsent(mut map) => {
match map.insert(key.clone(), QueryState::in_progress(runtime.id())) {
Some(QueryState::Memoized(old_memo)) => Some(old_memo),
Some(QueryState::InProgress { .. }) => unreachable!(),
None => None,
}
}
}
};
};
let panic_guard = PanicGuard::new(&self.map, key, descriptor, runtime);