sam-t2/sam/include/vtracer_async_queue.h

/*
* ========== Copyright Header Begin ==========================================
*
* OpenSPARC T2 Processor File: vtracer_async_queue.h
* Copyright (c) 2006 Sun Microsystems, Inc.  All Rights Reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES.
*
* The above named program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public
* License version 2 as published by the Free Software Foundation.
*
* The above named program is distributed in the hope that it will be
* useful, but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
* General Public License for more details.
*
* You should have received a copy of the GNU General Public
* License along with this work; if not, write to the Free Software
* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA.
*
* ========== Copyright Header End ============================================
*/
////////////////////////////////////////////////////////////
//
// File: vtracer_async_queue.h
//
// Copyright (C) 2001-2006 Sun Microsystems, Inc.
// All rights reserved.
//


// re-entrant queue structure for devices to send dma's, strings etc to the tracer
// this is the interface between blaze, the vcpu and devices (not relevant to tracer)

// use dd if=/dev/random | od -XN 8 to get the random suffix
#ifndef _vtracer_async_queue_h_8b214547ac275755_
#define _vtracer_async_queue_h_8b214547ac275755_

class vtracer_async_queue_el {
 public:

  vtracer_async_queue_el(const union vtracer_async_data_u * arg_data) {
    memcpy(&data, arg_data, sizeof(union vtracer_async_data_u));
    next = NULL;
  }

  union vtracer_async_data_u data;
  vtracer_async_queue_el * next;
}; // struct vtracer_async_queue_el


class vtracer_async_queue {

 public:
  vtracer_async_queue() {
    mutex_init(&mu, NULL, NULL);
    head = tail = NULL;
    qsize = 0;
  }

  // for fast, non-locking "single reader" use
  // example: if (trace_async_queue->getsize()) { dequeue(...); if (rtype_DMA) vtracer->dma(...); }
  // this avoids the lock/unlock operations when the queue is empty, which is the common case
  int getsize() {
    return qsize;
  }

  // use dequeue() in conjunction with getsize() for fast single-reader use
  // if multiple threads wish to dequeue, they must call mt_dequeue() instead of getsize() and dequeue()

  // WARNING: precondition: head != NULL. must enforce by calling is_empty before calling dequeue
  // WARNING: only one thread can "own" the queue - ie call is_empty() and dequeue().
  void dequeue(vtracer_async_data_u * data) {
    volatile vtracer_async_queue_el * el = head;

    mutex_lock(&mu);
    head = el->next;
    if (head == NULL) tail = NULL;
    qsize --;
    mutex_unlock(&mu);

    memcpy((void *) data, (void *) &el->data, sizeof(vtracer_async_data_u));
    delete el;
  } //   void dequeue(int &iswrite, uint64_t &paddr, int64_t &nbytes)


  // enqueue is called by (multiple) writer threads to add async records
  void enqueue(vtracer_async_data_u * data) {
    vtracer_async_queue_el * el = new vtracer_async_queue_el(data);

    mutex_lock(&mu);
    if (tail != NULL) {
      tail->next = el;
    } else {
      head = el;
    }
    tail = el;
    qsize ++;
    mutex_unlock(&mu);

  } //   void enqueue(int iswrite, uint64_t paddr, int64_t nbytes)


  // mt_dequeue atomically checks if the async queue is empty and dequeues the head if non-empty.
  // Use it if multiple threads want to read out of the queue.
  // Returns zero if queue was empty, positive otherwise. The number of records remaining is (return_value-1) or 0 if empty
  //
  // example: if (mt_dequeue(...)) if (dma) vtracer->dma(...); etc
  int mt_dequeue(vtracer_async_data_u * data) {
    mutex_lock(&mu);
    int rv = qsize;
    if (qsize) {
      volatile vtracer_async_queue_el * el = head;
      head = el->next;
      if (head == NULL) tail = NULL;
      qsize--;
      memcpy((void *) data, (void *) &el->data, sizeof(vtracer_async_data_u));
      delete el;
    }
    mutex_unlock(&mu);
    return rv;
  } //   int mt_dequeue(vtracer_async_data_u * data)

 private:
  mutex_t mu;

  volatile int qsize;
  volatile vtracer_async_queue_el * head;
  volatile vtracer_async_queue_el * tail;
}; // class vtracer_async_queue

// this is instantiated elsewhere in blaze initialization code
extern vtracer_async_queue * trace_async_queue;

#define TRACE_DMA(TD_iswrite, TD_nbytes, TD_pa, TD_devid) \
  if (g_vcpu[g_vcpu_id_max]->config.trace_on) {         \
      vtracer_async_data_u ad = {0};                    \
      ad.dma.rtype = vtracer_async_data_u::rtype_DMA;   \
      ad.dma.iswrite = TD_iswrite;                      \
      ad.dma.nbytes = TD_nbytes;                        \
      ad.dma.pa = TD_pa;                                \
      ad.dma.devid = TD_devid;                          \
      trace_async_queue->enqueue(&ad);                  \
  }


#endif // _vtracer_async_queue_h_8b214547ac275755_