ptw32_getprocessors.c

/*
 * ptw32_getprocessors.c
 *
 * Description:
 * This translation unit implements routines which are private to
 * the implementation and may be used throughout it.
 *
 * --------------------------------------------------------------------------
 *
 *      Pthreads4w - POSIX Threads for Windows
 *      Copyright 1998 John E. Bossom
 *      Copyright 1999-2018, Pthreads4w contributors
 *
 *      Homepage: https://sourceforge.net/projects/pthreads4w/
 *
 *      The current list of contributors is contained
 *      in the file CONTRIBUTORS included with the source
 *      code distribution. The list can also be seen at the
 *      following World Wide Web location:
 *
 *      https://sourceforge.net/p/pthreads4w/wiki/Contributors/
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#ifdef HAVE_CONFIG_H
# include <config.h>
#endif

#include "pthread.h"
#include "implement.h"


/*
 * __ptw32_getprocessors()
 *
 * Get the number of CPUs available to the process.
 *
 * If the available number of CPUs is 1 then pthread_spin_lock()
 * will block rather than spin if the lock is already owned.
 *
 * pthread_spin_init() calls this routine when initialising
 * a spinlock. If the number of available processors changes
 * (after a call to SetProcessAffinityMask()) then only
 * newly initialised spinlocks will notice.
 */
int
__ptw32_getprocessors (int *count)
{
  DWORD_PTR vProcessCPUs;
  DWORD_PTR vSystemCPUs;
  int result = 0;

#if defined(NEED_PROCESS_AFFINITY_MASK)

  *count = 1;

#else

  if (GetProcessAffinityMask (GetCurrentProcess (),
			      &vProcessCPUs, &vSystemCPUs))
    {
      DWORD_PTR bit;
      int CPUs = 0;

      for (bit = 1; bit != 0; bit <<= 1)
	{
	  if (vProcessCPUs & bit)
	    {
	      CPUs++;
	    }
	}
      *count = CPUs;
    }
  else
    {
      result = EAGAIN;
    }

#endif

  return (result);
}