text: /* signal_node.h                  -*-C++-*-
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  /**
   * @file signal_node.h
   *
   * @brief Signal nodes allow coordinated waking and sleeping of the runtime
   * without hammering on a single location in memory.
   *
   * The workers are logically arranged in a binary tree and propagate messages
   * leaf-ward.  User workers notify the root about waking and sleeping, so only
   * that one node need share a cache line with a user worker.
   */
  
  #ifndef INCLUDED_SIGNAL_NODE_DOT_H
  #define INCLUDED_SIGNAL_NODE_DOT_H
  
  #include "rts-common.h"
  #include <cilk/common.h>
  
  __CILKRTS_BEGIN_EXTERN_C
  
  /** Opaque type. */
  typedef struct signal_node_t signal_node_t;
  
  /**
   * Allocate and initialize a signal_node_t
   *
   * @return The initialized signal_node_t
   */
  COMMON_SYSDEP
  signal_node_t *signal_node_create(void);
  
  /**
   * Free any resources and deallocate a signal_node_t
   *
   * @param node The node to be deallocated.
   */
  COMMON_SYSDEP void signal_node_destroy(signal_node_t *node);
  
  /**
   * Test whether the node thinks the worker should go to sleep
   *
   * @param node The node to be tested.
   *
   * @return 1 If the worker should go to sleep
   * @return 0 If the worker should not go to sleep
   */
  COMMON_SYSDEP
  unsigned int signal_node_should_wait(signal_node_t *node);
  
  /**
   * Specify whether the worker should go to sleep
   *
   * @param node The node to be set.
   * @param msg The value to be set.  Valid values are:
   * - 0 - the worker should go to sleep
   * - 1 - the worker should stay active
   */
  COMMON_SYSDEP
  void signal_node_msg(signal_node_t *node, unsigned int msg);
  
  
  /**
   * Wait for the node to be set
   *
   * @param node The node to wait on
   */
  COMMON_SYSDEP
  void signal_node_wait(signal_node_t *node);
  
  __CILKRTS_END_EXTERN_C
  
  #endif // ! defined(INCLUDED_SIGNAL_NODE_DOT_H)
  