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Check that a query has not completed and is not executing before star…
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…ting it
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Zoxc committed Mar 8, 2023
1 parent 38b9655 commit 9555499
Showing 1 changed file with 21 additions and 6 deletions.
27 changes: 21 additions & 6 deletions compiler/rustc_query_system/src/query/plumbing.rs
Original file line number Diff line number Diff line change
Expand Up @@ -17,7 +17,7 @@ use rustc_data_structures::profiling::TimingGuard;
#[cfg(parallel_compiler)]
use rustc_data_structures::sharded::Sharded;
use rustc_data_structures::stack::ensure_sufficient_stack;
use rustc_data_structures::sync::Lock;
use rustc_data_structures::sync::{Lock, LockGuard};
use rustc_errors::{DiagnosticBuilder, ErrorGuaranteed, FatalError};
use rustc_session::Session;
use rustc_span::{Span, DUMMY_SP};
Expand Down Expand Up @@ -178,16 +178,13 @@ where
fn try_start<'b, Qcx>(
qcx: &'b Qcx,
state: &'b QueryState<K, Qcx::DepKind>,
mut state_lock: LockGuard<'b, FxHashMap<K, QueryResult<Qcx::DepKind>>>,
span: Span,
key: K,
) -> TryGetJob<'b, K, D>
where
Qcx: QueryContext + HasDepContext<DepKind = D>,
{
#[cfg(parallel_compiler)]
let mut state_lock = state.active.get_shard_by_value(&key).lock();
#[cfg(not(parallel_compiler))]
let mut state_lock = state.active.lock();
let lock = &mut *state_lock;
let current_job_id = qcx.current_query_job();

Expand Down Expand Up @@ -362,7 +359,25 @@ where
Qcx: QueryContext,
{
let state = query.query_state(qcx);
match JobOwner::<'_, Q::Key, Qcx::DepKind>::try_start(&qcx, state, span, key) {
#[cfg(parallel_compiler)]
let state_lock = state.active.get_shard_by_value(&key).lock();
#[cfg(not(parallel_compiler))]
let state_lock = state.active.lock();

// For the parallel compiler we need to check both the query cache and query state structures
// while holding the state lock to ensure that 1) the query has not yet completed and 2) the
// query is not still executing. Without checking the query cache here, we can end up
// re-executing the query since `try_start` only checks that the query is not currently
// executing, but another thread may have already completed the query and stores it result
// in the query cache.
if cfg!(parallel_compiler) && qcx.dep_context().sess().threads() > 1 {
if let Some((value, index)) = query.query_cache(qcx).lookup(&key) {
qcx.dep_context().profiler().query_cache_hit(index.into());
return (value, Some(index));
}
}

match JobOwner::<'_, Q::Key, Qcx::DepKind>::try_start(&qcx, state, state_lock, span, key) {
TryGetJob::NotYetStarted(job) => {
let (result, dep_node_index) = execute_job(query, qcx, key.clone(), dep_node, job.id);
let cache = query.query_cache(qcx);
Expand Down

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