[Openmp-commits] [PATCH] D15628: Prevent monitor thread creation when KMP_BLOCKTIME="infinite"

[Jonathan Peyton via Openmp-commits]

jlpeyton created this revision.
jlpeyton added reviewers: tlwilmar, AndreyChurbanov, hfinkel.
jlpeyton added a subscriber: openmp-commits.
jlpeyton set the repository for this revision to rL LLVM.

When users sets envirable KMP_BLOCKTIME to "infinite" (the time one busy-waits at barrieres, etc.), the monitor thread is not useful and can be ignored.  This change prevents the creation of the monitor thread when the users sets KMP_BLOCKTIME to "infinite".

Repository:
  rL LLVM

http://reviews.llvm.org/D15628

Files:
  runtime/src/z_Linux_util.c
  runtime/src/z_Windows_NT_util.c

Index: runtime/src/z_Windows_NT_util.c
===================================================================
--- runtime/src/z_Windows_NT_util.c
+++ runtime/src/z_Windows_NT_util.c
@@ -1429,6 +1429,14 @@
     DWORD               idThread;
     int                 ideal, new_ideal;
 
+    if( __kmp_dflt_blocktime == KMP_MAX_BLOCKTIME ) {
+        // We don't need monitor thread in case of MAX_BLOCKTIME
+        KA_TRACE( 10, ("__kmp_create_monitor: skipping monitor thread because of MAX blocktime\n" ) );
+        th->th.th_info.ds.ds_tid  = 0; // this makes reap_monitor no-op
+        th->th.th_info.ds.ds_gtid = 0;
+        TCW_4( __kmp_init_monitor, 2 ); // Signal to stop waiting for monitor creation
+        return;
+    }
     KA_TRACE( 10, ("__kmp_create_monitor: try to create monitor\n" ) );
 
     KMP_MB();       /* Flush all pending memory write invalidates.  */
@@ -1613,6 +1621,7 @@
     // If both tid and gtid are KMP_GTID_DNE, the monitor has been shut down.
     KMP_DEBUG_ASSERT( th->th.th_info.ds.ds_tid == th->th.th_info.ds.ds_gtid );
     if ( th->th.th_info.ds.ds_gtid != KMP_GTID_MONITOR ) {
+        KA_TRACE( 10, ("__kmp_reap_monitor: monitor did not start, returning\n") );
         return;
     }; // if
 
Index: runtime/src/z_Linux_util.c
===================================================================
--- runtime/src/z_Linux_util.c
+++ runtime/src/z_Linux_util.c
@@ -1123,6 +1123,13 @@
     int                 status;
     int                 auto_adj_size = FALSE;
 
+    if( __kmp_dflt_blocktime == KMP_MAX_BLOCKTIME ) {
+        // We don't need monitor thread in case of MAX_BLOCKTIME
+        KA_TRACE( 10, ("__kmp_create_monitor: skipping monitor thread because of MAX blocktime\n" ) );
+        th->th.th_info.ds.ds_tid  = 0; // this makes reap_monitor no-op
+        th->th.th_info.ds.ds_gtid = 0;
+        return;
+    }
     KA_TRACE( 10, ("__kmp_create_monitor: try to create monitor\n" ) );
 
     KMP_MB();       /* Flush all pending memory write invalidates.  */
@@ -1291,6 +1298,7 @@
     // If both tid and gtid are KMP_GTID_DNE, the monitor has been shut down.
     KMP_DEBUG_ASSERT( th->th.th_info.ds.ds_tid == th->th.th_info.ds.ds_gtid );
     if ( th->th.th_info.ds.ds_gtid != KMP_GTID_MONITOR ) {
+        KA_TRACE( 10, ("__kmp_reap_monitor: monitor did not start, returning\n") );
         return;
     }; // if
 


-------------- next part --------------
A non-text attachment was scrubbed...
Name: D15628.43186.patch
Type: text/x-patch
Size: 2376 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/openmp-commits/attachments/20151217/33e4c0e1/attachment.bin>