[OpenMP] Add omp_pause_resource* API

Add omp_pause_resource and omp_pause_resource_all API and enum, plus stub for
internal implementation. Implemented callable helper function to do local pause,
and added basic functionality for hard and soft pause.

Patch by Terry Wilmarth

Differential Revision: https://reviews.llvm.org/D55078

llvm-svn: 351372

1 files changed, 99 insertions, 3 deletions

diff --git a/openmp/runtime/src/kmp_runtime.cpp b/openmp/runtime/src/kmp_runtime.cpp
index 0db376159fc..821012bb3d4 100644
--- a/openmp/runtime/src/kmp_runtime.cpp
+++ b/openmp/runtime/src/kmp_runtime.cpp
@@ -752,6 +752,10 @@ int __kmp_enter_single(int gtid, ident_t *id_ref, int push_ws) {
   if (!TCR_4(__kmp_init_parallel))
     __kmp_parallel_initialize();
 
+#if OMP_50_ENABLED
+  __kmp_resume_if_soft_paused();
+#endif
+
   th = __kmp_threads[gtid];
   team = th->th.th_team;
   status = 0;
@@ -1189,6 +1193,10 @@ void __kmp_serialized_parallel(ident_t *loc, kmp_int32 global_tid) {
   if (!TCR_4(__kmp_init_parallel))
     __kmp_parallel_initialize();
 
+#if OMP_50_ENABLED
+  __kmp_resume_if_soft_paused();
+#endif
+
   this_thr = __kmp_threads[global_tid];
   serial_team = this_thr->th.th_serial_team;
 
@@ -1492,6 +1500,10 @@ int __kmp_fork_call(ident_t *loc, int gtid,
     if (!TCR_4(__kmp_init_parallel))
       __kmp_parallel_initialize();
 
+#if OMP_50_ENABLED
+    __kmp_resume_if_soft_paused();
+#endif
+
     /* setup current data */
     master_th = __kmp_threads[gtid]; // AC: potentially unsafe, not in sync with
     // shutdown
@@ -5851,7 +5863,6 @@ static void __kmp_reap_thread(kmp_info_t *thread, int is_root) {
   gtid = thread->th.th_info.ds.ds_gtid;
 
   if (!is_root) {
-
     if (__kmp_dflt_blocktime != KMP_MAX_BLOCKTIME) {
       /* Assume the threads are at the fork barrier here */
       KA_TRACE(
@@ -6272,8 +6283,10 @@ void __kmp_internal_end_thread(int gtid_req) {
   // OM: Removed Linux* OS restriction to fix the crash on OS X* (DPD200239966)
   // and Windows(DPD200287443) that occurs when using critical sections from
   // foreign threads.
-  KA_TRACE(10, ("__kmp_internal_end_thread: exiting T#%d\n", gtid_req));
-  return;
+  if (__kmp_pause_status != kmp_hard_paused) {
+    KA_TRACE(10, ("__kmp_internal_end_thread: exiting T#%d\n", gtid_req));
+    return;
+  }
 #endif
   /* synchronize the termination process */
   __kmp_acquire_bootstrap_lock(&__kmp_initz_lock);
@@ -6920,6 +6933,10 @@ void __kmp_parallel_initialize(void) {
     __kmp_do_middle_initialize();
   }
 
+#if OMP_50_ENABLED
+  __kmp_resume_if_hard_paused();
+#endif
+
   /* begin initialization */
   KA_TRACE(10, ("__kmp_parallel_initialize: enter\n"));
   KMP_ASSERT(KMP_UBER_GTID(gtid));
@@ -8190,3 +8207,82 @@ __kmp_determine_reduction_method(
 kmp_int32 __kmp_get_reduce_method(void) {
   return ((__kmp_entry_thread()->th.th_local.packed_reduction_method) >> 8);
 }
+
+#if OMP_50_ENABLED
+
+// Soft pause sets up threads to ignore blocktime and just go to sleep.
+// Spin-wait code checks __kmp_pause_status and reacts accordingly.
+void __kmp_soft_pause() { __kmp_pause_status = kmp_soft_paused; }
+
+// Hard pause shuts down the runtime completely.  Resume happens naturally when
+// OpenMP is used subsequently.
+void __kmp_hard_pause() {
+  __kmp_pause_status = kmp_hard_paused;
+  __kmp_internal_end_thread(-1);
+}
+
+// Soft resume sets __kmp_pause_status, and wakes up all threads.
+void __kmp_resume_if_soft_paused() {
+  if (__kmp_pause_status == kmp_soft_paused) {
+    __kmp_pause_status = kmp_not_paused;
+
+    for (int gtid = 1; gtid < __kmp_threads_capacity; ++gtid) {
+      kmp_info_t *thread = __kmp_threads[gtid];
+      if (thread) { // Wake it if sleeping
+        kmp_flag_64 fl(&thread->th.th_bar[bs_forkjoin_barrier].bb.b_go, thread);
+        if (fl.is_sleeping())
+          fl.resume(gtid);
+        else if (__kmp_try_suspend_mx(thread)) { // got suspend lock
+          __kmp_unlock_suspend_mx(thread); // unlock it; it won't sleep
+        } else { // thread holds the lock and may sleep soon
+          do { // until either the thread sleeps, or we can get the lock
+            if (fl.is_sleeping()) {
+              fl.resume(gtid);
+              break;
+            } else if (__kmp_try_suspend_mx(thread)) {
+              __kmp_unlock_suspend_mx(thread);
+              break;
+            }
+          } while (1);
+        }
+      }
+    }
+  }
+}
+
+// This function is called via __kmpc_pause_resource. Returns 0 if successful.
+// TODO: add warning messages
+int __kmp_pause_resource(kmp_pause_status_t level) {
+  if (level == kmp_not_paused) { // requesting resume
+    if (__kmp_pause_status == kmp_not_paused) {
+      // error message about runtime not being paused, so can't resume
+      return 1;
+    } else {
+      KMP_DEBUG_ASSERT(__kmp_pause_status == kmp_soft_paused ||
+                       __kmp_pause_status == kmp_hard_paused);
+      __kmp_pause_status = kmp_not_paused;
+      return 0;
+    }
+  } else if (level == kmp_soft_paused) { // requesting soft pause
+    if (__kmp_pause_status != kmp_not_paused) {
+      // error message about already being paused
+      return 1;
+    } else {
+      __kmp_soft_pause();
+      return 0;
+    }
+  } else if (level == kmp_hard_paused) { // requesting hard pause
+    if (__kmp_pause_status != kmp_not_paused) {
+      // error message about already being paused
+      return 1;
+    } else {
+      __kmp_hard_pause();
+      return 0;
+    }
+  } else {
+    // error message about invalid level
+    return 1;
+  }
+}
+
+#endif // OMP_50_ENABLED