[Openmp-commits] [openmp] r256061 - Prevent monitor thread creation when KMP_BLOCKTIME="infinite"

[Jonathan Peyton via Openmp-commits]

Author: jlpeyton
Date: Fri Dec 18 17:20:36 2015
New Revision: 256061

URL: http://llvm.org/viewvc/llvm-project?rev=256061&view=rev
Log:
Prevent monitor thread creation when KMP_BLOCKTIME="infinite"

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".

Differential Revision: http://reviews.llvm.org/D15628

Modified:
    openmp/trunk/runtime/src/z_Linux_util.c
    openmp/trunk/runtime/src/z_Windows_NT_util.c

Modified: openmp/trunk/runtime/src/z_Linux_util.c
URL: http://llvm.org/viewvc/llvm-project/openmp/trunk/runtime/src/z_Linux_util.c?rev=256061&r1=256060&r2=256061&view=diff
==============================================================================
--- openmp/trunk/runtime/src/z_Linux_util.c (original)
+++ openmp/trunk/runtime/src/z_Linux_util.c Fri Dec 18 17:20:36 2015
@@ -1123,6 +1123,13 @@ __kmp_create_monitor( kmp_info_t *th )
     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 @@ __kmp_reap_monitor( kmp_info_t *th )
     // 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
 

Modified: openmp/trunk/runtime/src/z_Windows_NT_util.c
URL: http://llvm.org/viewvc/llvm-project/openmp/trunk/runtime/src/z_Windows_NT_util.c?rev=256061&r1=256060&r2=256061&view=diff
==============================================================================
--- openmp/trunk/runtime/src/z_Windows_NT_util.c (original)
+++ openmp/trunk/runtime/src/z_Windows_NT_util.c Fri Dec 18 17:20:36 2015
@@ -1429,6 +1429,14 @@ __kmp_create_monitor( kmp_info_t *th )
     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 @@ __kmp_reap_monitor( kmp_info_t *th )
     // 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