Merge pull request #793 from ScorexFoundation/fix-i778

Fix possible race condition in PrecompiledScriptReducer

core/src/main/scala/scalan/Base.scala

@@ -709,7 +709,14 @@ abstract class Base { scalan: Scalan =>
       cfor(0)(_ < delta, _ + 1) { _ => tab.append(null) }
       val sym = if (s == null) new SingleRef(d) else s
       tab += sym
-      assert(tab.length == id + 1)
+      assert(tab.length == id + 1,
+        s"""tab.length == id + 1:
+          |tab.length = ${tab.length}
+          |id = $id
+          |s = $s
+          |d = $d
+          |sym = $sym
+          |""".stripMargin)
       sym
     }
   }
@@ -781,7 +788,6 @@ abstract class Base { scalan: Scalan =>
     if (sym == null) {
       sym = createDefinition(optScope, newSym, d)
     }
-//    assert(te.rhs == d, s"${if (te !) "Found" else "Created"} unequal definition ${te.rhs} with symbol ${te.sym.toStringWithType} for $d")
     sym
   }
 
@@ -792,15 +798,36 @@ abstract class Base { scalan: Scalan =>
     * @return  reference to `d` (which is `s`)
     */
   protected def createDefinition[T](optScope: Nullable[ThunkScope], s: Ref[T], d: Def[T]): Ref[T] = {
-    assert(_symbolTable(d.nodeId).node.nodeId == d.nodeId)
-    assert(s.node eq d, s"Inconsistent Sym -> Def pair $s -> $d")
-    optScope match {
-      case Nullable(scope) =>
-        scope += s
-      case _ =>
-        _globalDefs.put(d, d)
+    try {
+      val nodeId = d.nodeId
+      val tableSym = _symbolTable(nodeId)
+      assert(tableSym.node.nodeId == nodeId)
+      assert(s.node eq d, s"Inconsistent Sym -> Def pair $s -> $d")
+      optScope match {
+        case Nullable(scope) =>
+          scope += s
+        case _ =>
+          _globalDefs.put(d, d)
+      }
+      s
+    } catch { case t: Throwable =>
+      val msg = new mutable.StringBuilder(
+        s"""optScope = $optScope
+        |s = $s
+        |d = $d""".stripMargin)
+      if (d != null) {
+        msg ++= s"\nd.nodeId = ${d.nodeId}"
+        val tableSym = _symbolTable(d.nodeId)
+        msg ++= s"\n_symbolTable(d.nodeId) = $tableSym"
+        if (tableSym != null) {
+          msg ++= s"\ntableSym.node = ${tableSym.node}"
+          if (tableSym.node != null) {
+            msg ++= s"\ntableSym.node.nodeId = ${tableSym.node.nodeId}"
+          }
+        }
+      }
+      throw new RuntimeException(msg.result(), t)
     }
-    s
   }
 
   /**

sigmastate/src/main/scala/sigmastate/eval/IRContext.scala

@@ -1,19 +1,23 @@
 package sigmastate.eval
 
-import java.lang.{Math => JMath}
 import sigmastate.SType
-import sigmastate.Values.{Value, SValue}
+import sigmastate.Values.{SValue, Value}
 import sigmastate.interpreter.Interpreter.ScriptEnv
 import sigmastate.lang.TransformingSigmaBuilder
 import sigmastate.lang.exceptions.CostLimitException
+import sigmastate.utils.Helpers
 import sigmastate.utxo.CostTable
 
+import java.util.concurrent.locks.ReentrantLock
 import scala.util.Try
 
 trait IRContext extends Evaluation with TreeBuilding {
 
   override val builder = TransformingSigmaBuilder
 
+  /** Can be used to synchronize access to this IR object from multiple threads. */
+  val lock = new ReentrantLock()
+
   /** Pass configuration which is used to turn-off constant propagation.
     * @see `beginPass(noCostPropagationPass)`  */
   lazy val noConstPropagationPass = new DefaultPass(
@@ -125,9 +129,12 @@ trait IRContext extends Evaluation with TreeBuilding {
     */
   def checkCostWithContext(ctx: SContext,
                 costF: Ref[((Context, (Int, Size[Context]))) => Int], maxCost: Long, initCost: Long): Try[Int] = Try {
-    val costFun = compile[(SContext, (Int, SSize[SContext])), Int, (Context, (Int, Size[Context])), Int](
-                    getDataEnv, costF, Some(maxCost))
-    val (estimatedCost, accCost) = costFun((ctx, (0, Sized.sizeOf(ctx))))
+
+    val (estimatedCost, accCost) = Helpers.withReentrantLock(lock) { // protect mutable access to this IR
+      val costFun = compile[(SContext, (Int, SSize[SContext])), Int, (Context, (Int, Size[Context])), Int](
+        getDataEnv, costF, Some(maxCost))
+      costFun((ctx, (0, Sized.sizeOf(ctx))))
+    }
 
     if (debugModeSanityChecks) {
       if (estimatedCost != accCost)

sigmastate/src/main/scala/sigmastate/interpreter/PrecompiledScriptProcessor.scala

@@ -2,17 +2,17 @@ package sigmastate.interpreter
 
 import java.util.concurrent.ExecutionException
 import java.util.concurrent.atomic.AtomicInteger
-
-import com.google.common.cache.{CacheBuilder, RemovalNotification, RemovalListener, LoadingCache, CacheLoader, CacheStats}
+import com.google.common.cache.{CacheBuilder, CacheLoader, CacheStats, LoadingCache, RemovalListener, RemovalNotification}
 import org.ergoplatform.settings.ErgoAlgos
 import org.ergoplatform.validation.SigmaValidationSettings
-import org.ergoplatform.validation.ValidationRules.{CheckCostFunc, CheckCalcFunc, trySoftForkable}
+import org.ergoplatform.validation.ValidationRules.{CheckCalcFunc, CheckCostFunc, trySoftForkable}
 import scalan.{AVHashMap, Nullable}
 import sigmastate.Values
 import sigmastate.Values.ErgoTree
-import sigmastate.eval.{RuntimeIRContext, IRContext}
+import sigmastate.eval.{IRContext, RuntimeIRContext}
 import sigmastate.interpreter.Interpreter.{ReductionResult, WhenSoftForkReductionResult}
 import sigmastate.serialization.ErgoTreeSerializer
+import sigmastate.utils.Helpers
 import sigmastate.utils.Helpers._
 import spire.syntax.all.cfor
 
@@ -84,9 +84,11 @@ case class PrecompiledScriptReducer(scriptBytes: Seq[Byte])(implicit val IR: IRC
       val estimatedCost = IR.checkCostWithContext(costingCtx, costF, maxCost, initCost).getOrThrow
 
       // check calc
-      val calcF = costingRes.calcF
       val calcCtx = context.toSigmaContext(isCost = false)
-      val res = Interpreter.calcResult(IR)(calcCtx, calcF)
+      val res = Helpers.withReentrantLock(IR.lock) { // protecting mutable access to IR instance
+        val calcF = costingRes.calcF
+        Interpreter.calcResult(IR)(calcCtx, calcF)
+      }
       ReductionResult(SigmaDsl.toSigmaBoolean(res), estimatedCost)
     }
   }

sigmastate/src/main/scala/sigmastate/utils/Helpers.scala

@@ -1,16 +1,16 @@
 package sigmastate.utils
 
-import java.util
-
 import io.circe.Decoder
 import org.ergoplatform.settings.ErgoAlgos
 import sigmastate.eval.{Colls, SigmaDsl}
 import sigmastate.interpreter.CryptoConstants.EcPointType
 import special.collection.Coll
 import special.sigma.GroupElement
 
+import java.util
+import java.util.concurrent.locks.Lock
 import scala.reflect.ClassTag
-import scala.util.{Failure, Try, Either, Success, Right}
+import scala.util.{Either, Failure, Right, Success, Try}
 
 object Helpers {
   def xor(ba1: Array[Byte], ba2: Array[Byte]): Array[Byte] = ba1.zip(ba2).map(t => (t._1 ^ t._2).toByte)
@@ -158,6 +158,27 @@ object Helpers {
     val bytes = ErgoAlgos.decodeUnsafe(base16String)
     Colls.fromArray(bytes)
   }
+
+  /**
+    * Executes the given block with a reentrant mutual exclusion Lock with the same basic
+    * behavior and semantics as the implicit monitor lock accessed using synchronized
+    * methods and statements in Java.
+    *
+    * Note, using this method has an advantage of having this method in a stack trace in case of
+    * an exception in the block.
+    * @param l lock object which should be acquired by the current thread before block can start executing
+    * @param block block of code which will be executed retaining the lock
+    * @return the value produced by the block
+    */
+  def withReentrantLock[A](l: Lock)(block: => A): A = {
+    l.lock()
+    val res = try
+      block
+    finally {
+      l.unlock()
+    }
+    res
+  }
 }
 
 object Overloading {