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new d7abddc454ff [SPARK-49808][SQL] Fix a deadlock in subquery execution
due to lazy vals
d7abddc454ff is described below
commit d7abddc454ffef6ac16e8f6df6f601eec621ddfd
Author: Ruifeng Zheng <[email protected]>
AuthorDate: Fri Sep 27 21:53:10 2024 +0800
[SPARK-49808][SQL] Fix a deadlock in subquery execution due to lazy vals
### What changes were proposed in this pull request?
Fix a deadlock in subquery execution due to lazy vals
### Why are the changes needed?
we observed a deadlock between `QueryPlan.canonicalized` and
`QueryPlan.references`:
```
24/09/04 04:46:54 ERROR DeadlockDetector: Found 2 new deadlock thread(s):
"ScalaTest-run-running-SubquerySuite" prio=5 Id=1 BLOCKED on
org.apache.spark.sql.execution.aggregate.HashAggregateExec87abc7f owned by
"subquery-5" Id=112
at
app//org.apache.spark.sql.catalyst.plans.QueryPlan.canonicalized$lzycompute(QueryPlan.scala:684)
- blocked on
org.apache.spark.sql.execution.aggregate.HashAggregateExec87abc7f
at
app//org.apache.spark.sql.catalyst.plans.QueryPlan.canonicalized(QueryPlan.scala:684)
at
app//org.apache.spark.sql.catalyst.plans.QueryPlan.$anonfun$doCanonicalize$2(QueryPlan.scala:716)
at
app//org.apache.spark.sql.catalyst.plans.QueryPlan$$Lambda$4058/0x00007f740f3d0cb0.apply(Unknown
Source)
at
app//org.apache.spark.sql.catalyst.trees.UnaryLike.mapChildren(TreeNode.scala:1314)
at
app//org.apache.spark.sql.catalyst.trees.UnaryLike.mapChildren$(TreeNode.scala:1313)
at
app//org.apache.spark.sql.execution.WholeStageCodegenExec.mapChildren(WholeStageCodegenExec.scala:639)
at
app//org.apache.spark.sql.catalyst.plans.QueryPlan.doCanonicalize(QueryPlan.scala:716)
...
"subquery-5" daemon prio=5 Id=112 BLOCKED on
org.apache.spark.sql.execution.WholeStageCodegenExec132a3243 owned by
"ScalaTest-run-running-SubquerySuite" Id=1
at
app//org.apache.spark.sql.catalyst.plans.QueryPlan.references$lzycompute(QueryPlan.scala:101)
- blocked on
org.apache.spark.sql.execution.WholeStageCodegenExec132a3243
at
app//org.apache.spark.sql.catalyst.plans.QueryPlan.references(QueryPlan.scala:101)
at
app//org.apache.spark.sql.execution.CodegenSupport.usedInputs(WholeStageCodegenExec.scala:325)
at
app//org.apache.spark.sql.execution.CodegenSupport.usedInputs$(WholeStageCodegenExec.scala:325)
at
app//org.apache.spark.sql.execution.WholeStageCodegenExec.usedInputs(WholeStageCodegenExec.scala:639)
at
app//org.apache.spark.sql.execution.CodegenSupport.consume(WholeStageCodegenExec.scala:187)
at
app//org.apache.spark.sql.execution.CodegenSupport.consume$(WholeStageCodegenExec.scala:157)
at
app//org.apache.spark.sql.execution.aggregate.HashAggregateExec.consume(HashAggregateExec.scala:53)
```
The main thread `TakeOrderedAndProject.doExecute` is trying to compute
`outputOrdering`, it top-down traverse the tree, and requires the lock of
`QueryPlan.canonicalized` in the path.
In this deadlock, it successfully obtained the lock of
`WholeStageCodegenExec` and requires the lock of `HashAggregateExec`;
Concurrently, a subquery execution thread is performing code generation and
bottom-up traverses the tree via `def consume`, which checks
`WholeStageCodegenExec.usedInputs` and refererences a lazy val
`QueryPlan.references`. It requires the lock of `QueryPlan.references` in the
path.
In this deadlock, it successfully obtained the lock of `HashAggregateExec`
and requires the lock of `WholeStageCodegenExec`;
This is due to Scala's lazy val internally calls this.synchronized on the
instance that contains the val. This creates a potential for deadlocks.
### Does this PR introduce _any_ user-facing change?
no
### How was this patch tested?
manually checked with `com.databricks.spark.sql.SubquerySuite`
we encountered this issue multiple times before this fix in
`SubquerySuite`, and after this fix we didn't hit this issue in multiple runs.
### Was this patch authored or co-authored using generative AI tooling?
no
Closes #48279 from zhengruifeng/fix_deadlock.
Authored-by: Ruifeng Zheng <[email protected]>
Signed-off-by: Wenchen Fan <[email protected]>
---
.../main/scala/org/apache/spark/sql/catalyst/plans/QueryPlan.scala | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)
diff --git
a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/plans/QueryPlan.scala
b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/plans/QueryPlan.scala
index 3f417644082c..ca5ff78b10e9 100644
---
a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/plans/QueryPlan.scala
+++
b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/plans/QueryPlan.scala
@@ -32,6 +32,7 @@ import org.apache.spark.sql.catalyst.trees.TreePatternBits
import org.apache.spark.sql.catalyst.types.DataTypeUtils
import org.apache.spark.sql.internal.SQLConf
import org.apache.spark.sql.types.{DataType, StructType}
+import org.apache.spark.util.LazyTry
import org.apache.spark.util.collection.BitSet
/**
@@ -94,9 +95,11 @@ abstract class QueryPlan[PlanType <: QueryPlan[PlanType]]
* All Attributes that appear in expressions from this operator. Note that
this set does not
* include attributes that are implicitly referenced by being passed through
to the output tuple.
*/
+ def references: AttributeSet = lazyReferences.get
+
@transient
- lazy val references: AttributeSet = {
- AttributeSet.fromAttributeSets(expressions.map(_.references)) --
producedAttributes
+ private val lazyReferences = LazyTry {
+ AttributeSet(expressions) -- producedAttributes
}
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