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Bug fix for hang when tasks used in nested parallel

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Bug fix for hang when omp task and nested parallelism used together.
Still some problem remains with task state saving/restoring, but
user's case works fine now. All tasking unit tests passed as well.

Patch by Andrey Churbanov

Differential Revision: http://reviews.llvm.org/D21558

llvm-svn: 273297
This commit is contained in:
Jonathan Peyton
2016-06-21 19:12:07 +00:00
parent 93b4b2e386
commit c76f9f0df8
2 changed files with 35 additions and 3 deletions
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6
openmp/runtime/src/kmp_runtime.c
View File

@@ -1459,8 +1459,8 @@ __kmp_fork_call(
// Nested level will be an index in the nested nthreads array
level = parent_team->t.t_level;
#if OMP_40_ENABLED
active_level = parent_team->t.t_active_level; // is used to launch non-serial teams even if nested is not allowed
#if OMP_40_ENABLED
teams_level = master_th->th.th_teams_level; // needed to check nesting inside the teams
#endif
#if KMP_NESTED_HOT_TEAMS
@@ -2051,7 +2051,7 @@ __kmp_fork_call(
__kmp_gtid_from_thread( master_th ), master_th->th.th_task_team,
parent_team, team->t.t_task_team[master_th->th.th_task_state], team ) );
if ( level || master_th->th.th_task_team ) {
if ( active_level || master_th->th.th_task_team ) {
// Take a memo of master's task_state
KMP_DEBUG_ASSERT(master_th->th.th_task_state_memo_stack);
if (master_th->th.th_task_state_top >= master_th->th.th_task_state_stack_sz) { // increase size
@@ -2074,7 +2074,7 @@ __kmp_fork_call(
master_th->th.th_task_state_memo_stack[master_th->th.th_task_state_top] = master_th->th.th_task_state;
master_th->th.th_task_state_top++;
#if KMP_NESTED_HOT_TEAMS
if (team == master_th->th.th_hot_teams[level].hot_team) { // Restore master's nested state if nested hot team
if (team == master_th->th.th_hot_teams[active_level].hot_team) { // Restore master's nested state if nested hot team
master_th->th.th_task_state = master_th->th.th_task_state_memo_stack[master_th->th.th_task_state_top];
}
else {

32
openmp/runtime/test/tasking/nested_parallel_tasking.c Normal file
View File

@@ -0,0 +1,32 @@
// RUN: %libomp-compile-and-run
#include <stdio.h>
#include <omp.h>
/*
* This test would hang when level instead of active level
* used to push task state.
*/
int main()
{
// If num_threads is changed to a value greater than 1, then the test passes
#pragma omp parallel num_threads(1)
{
#pragma omp parallel
printf("Hello World from thread %d\n", omp_get_thread_num());
}
printf("omp_num_threads: %d\n", omp_get_max_threads());
#pragma omp parallel
{
#pragma omp master
#pragma omp task default(none)
{
printf("%d is executing this task\n", omp_get_thread_num());
}
}
printf("pass\n");
return 0;
}