Cygwin: Implement sched_[gs]etaffinity()

This patch set implements the Linux syscalls sched_getaffinity,
sched_setaffinity, pthread_getaffinity_np, and pthread_setaffinity_np.
Linux has a straightforward view of the cpu sets used in affinity masks.
They are simply long (1024-bit) bit masks.  This code emulates that view
while internally dealing with Windows' distribution of available CPUs among
processor groups.

1 files changed, 16 insertions, 4 deletions

diff --git a/winsup/cygwin/miscfuncs.cc b/winsup/cygwin/miscfuncs.cc
index b5dfffc..e02bc9c 100644
--- a/winsup/cygwin/miscfuncs.cc
+++ b/winsup/cygwin/miscfuncs.cc
@@ -963,17 +963,19 @@ SetThreadName(DWORD dwThreadID, const char* threadName)
 
 #define add_size(p,s) ((p) = ((__typeof__(p))((PBYTE)(p)+(s))))
 
+static WORD num_cpu_per_group = 0;
+static WORD group_count = 0;
+
 WORD
 __get_cpus_per_group (void)
 {
-  static WORD num_cpu_per_group = 0;
-
   tmp_pathbuf tp;
 
   if (num_cpu_per_group)
     return num_cpu_per_group;
 
   num_cpu_per_group = 64;
+  group_count = 1;
 
   PSYSTEM_LOGICAL_PROCESSOR_INFORMATION_EX lpi =
             (PSYSTEM_LOGICAL_PROCESSOR_INFORMATION_EX) tp.c_get ();
@@ -1005,10 +1007,20 @@ __get_cpus_per_group (void)
 	   actually available CPUs.  The ActiveProcessorCount is correct
 	   though.  So we just use ActiveProcessorCount for now, hoping for
 	   the best. */
-        num_cpu_per_group
-                = plpi->Group.GroupInfo[0].ActiveProcessorCount;
+        num_cpu_per_group = plpi->Group.GroupInfo[0].ActiveProcessorCount;
+
+	/* Follow that lead to get the group count. */
+	group_count = plpi->Group.ActiveGroupCount;
         break;
       }
 
   return num_cpu_per_group;
 }
+
+WORD
+__get_group_count (void)
+{
+  if (group_count == 0)
+    (void) __get_cpus_per_group (); // caller should have called this first
+  return group_count;
+}