[Openmp-commits] [PATCH] D23115: __kmp_free_task: Fix for serial explicit tasks producing proxy tasks

[Jonas Hahnfeld via Openmp-commits]

Hahnfeld created this revision.
Hahnfeld added reviewers: jlpeyton, AndreyChurbanov.
Hahnfeld added a subscriber: openmp-commits.

Consider the following code which may be executed by a serial team:

```
int dep;
#pragma omp target nowait depend(out: dep)
{
    sleep(1);
}
#pragma omp task depend(in: dep)
{
    #pragma omp target nowait
    {
        sleep(1);
    }
}
```

Here the explicit task may not be freed until the nested proxy task has
finished. The current code hasn't considered this and called __kmp_free_task
anyway which triggered an assert because of remaining incomplete children:

```
KMP_DEBUG_ASSERT( TCR_4(taskdata->td_incomplete_child_tasks) == 0 );
```

https://reviews.llvm.org/D23115

Files:
  runtime/src/kmp_tasking.c

Index: runtime/src/kmp_tasking.c
===================================================================
--- runtime/src/kmp_tasking.c
+++ runtime/src/kmp_tasking.c
@@ -576,15 +576,10 @@
 static void
 __kmp_free_task_and_ancestors( kmp_int32 gtid, kmp_taskdata_t * taskdata, kmp_info_t * thread )
 {
-    kmp_int32 children = 0;
-    kmp_int32 team_or_tasking_serialized = taskdata -> td_flags.team_serial || taskdata -> td_flags.tasking_ser;
-
     KMP_DEBUG_ASSERT( taskdata -> td_flags.tasktype == TASK_EXPLICIT );
 
-    if ( !team_or_tasking_serialized ) {
-        children = KMP_TEST_THEN_DEC32( (kmp_int32 *)(& taskdata -> td_allocated_child_tasks) ) - 1;
-        KMP_DEBUG_ASSERT( children >= 0 );
-    }
+    kmp_int32 children = KMP_TEST_THEN_DEC32( (kmp_int32 *)(& taskdata -> td_allocated_child_tasks) ) - 1;
+    KMP_DEBUG_ASSERT( children >= 0 );
 
     // Now, go up the ancestor tree to see if any ancestors can now be freed.
     while ( children == 0 )
@@ -599,16 +594,14 @@
 
         taskdata = parent_taskdata;
 
-        // Stop checking ancestors at implicit task or if tasking serialized
+        // Stop checking ancestors at implicit task
         // instead of walking up ancestor tree to avoid premature deallocation of ancestors.
-        if ( team_or_tasking_serialized || taskdata -> td_flags.tasktype == TASK_IMPLICIT )
+        if ( taskdata -> td_flags.tasktype == TASK_IMPLICIT )
             return;
 
-        if ( !team_or_tasking_serialized ) {
-            // Predecrement simulated by "- 1" calculation
-            children = KMP_TEST_THEN_DEC32( (kmp_int32 *)(& taskdata -> td_allocated_child_tasks) ) - 1;
-            KMP_DEBUG_ASSERT( children >= 0 );
-        }
+        // Predecrement simulated by "- 1" calculation
+        children = KMP_TEST_THEN_DEC32( (kmp_int32 *)(& taskdata -> td_allocated_child_tasks) ) - 1;
+        KMP_DEBUG_ASSERT( children >= 0 );
     }
 
     KA_TRACE(20, ("__kmp_free_task_and_ancestors(exit): T#%d task %p has %d children; "


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