FreeBSD/Linux Kernel Cross Reference
sys/contrib/vchiq/interface/vchiq_arm/vchiq_util.c

     /**
      * Copyright (c) 2010-2012 Broadcom. All rights reserved.
      *
      * Redistribution and use in source and binary forms, with or without
      * modification, are permitted provided that the following conditions
      * are met:
      * 1. Redistributions of source code must retain the above copyright
      *    notice, this list of conditions, and the following disclaimer,
      *    without modification.
     * 2. Redistributions in binary form must reproduce the above copyright
     *    notice, this list of conditions and the following disclaimer in the
     *    documentation and/or other materials provided with the distribution.
     * 3. The names of the above-listed copyright holders may not be used
     *    to endorse or promote products derived from this software without
     *    specific prior written permission.
     *
     * ALTERNATIVELY, this software may be distributed under the terms of the
     * GNU General Public License ("GPL") version 2, as published by the Free
     * Software Foundation.
     *
     * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
     * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
     * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
     * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
     * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
     * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
     * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
     * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
     * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
     * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
     * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     */
    
    #include "vchiq_util.h"
    
    static inline int is_pow2(int i)
    {
            return i && !(i & (i - 1));
    }
    
    int vchiu_queue_init(VCHIU_QUEUE_T *queue, int size)
    {
            WARN_ON(!is_pow2(size));
    
            queue->size = size;
            queue->read = 0;
            queue->write = 0;
            queue->initialized = 1;
    
            _sema_init(&queue->pop, 0);
            _sema_init(&queue->push, 0);
    
            queue->storage = kzalloc(size * sizeof(VCHIQ_HEADER_T *), GFP_KERNEL);
            if (queue->storage == NULL) {
                    vchiu_queue_delete(queue);
                    return 0;
            }
            return 1;
    }
    
    void vchiu_queue_delete(VCHIU_QUEUE_T *queue)
    {
            if (queue->storage != NULL)
                    kfree(queue->storage);
    }
    
    int vchiu_queue_is_empty(VCHIU_QUEUE_T *queue)
    {
            return queue->read == queue->write;
    }
    
    int vchiu_queue_is_full(VCHIU_QUEUE_T *queue)
    {
            return queue->write == queue->read + queue->size;
    }
    
    void vchiu_queue_push(VCHIU_QUEUE_T *queue, VCHIQ_HEADER_T *header)
    {
            if (!queue->initialized)
                    return;
    
            while (queue->write == queue->read + queue->size) {
                    if (down_interruptible(&queue->pop) != 0) {
                            flush_signals(current);
                    }
            }
    
            /*
             * Write to queue->storage must be visible after read from
             * queue->read
             */
            smp_mb();
    
            queue->storage[queue->write & (queue->size - 1)] = header;
    
            /*
             * Write to queue->storage must be visible before write to
             * queue->write
             */
           smp_wmb();
   
           queue->write++;
   
           up(&queue->push);
   }
   
   VCHIQ_HEADER_T *vchiu_queue_peek(VCHIU_QUEUE_T *queue)
   {
           while (queue->write == queue->read) {
                   if (down_interruptible(&queue->push) != 0) {
                           flush_signals(current);
                   }
           }
   
           up(&queue->push); // We haven't removed anything from the queue.
   
           /*
            * Read from queue->storage must be visible after read from
            * queue->write
            */
           smp_rmb();
   
           return queue->storage[queue->read & (queue->size - 1)];
   }
   
   VCHIQ_HEADER_T *vchiu_queue_pop(VCHIU_QUEUE_T *queue)
   {
           VCHIQ_HEADER_T *header;
   
           while (queue->write == queue->read) {
                   if (down_interruptible(&queue->push) != 0) {
                           flush_signals(current);
                   }
           }
   
           /*
            * Read from queue->storage must be visible after read from
            * queue->write
            */
           smp_rmb();
   
           header = queue->storage[queue->read & (queue->size - 1)];
   
           /*
            * Read from queue->storage must be visible before write to
            * queue->read
            */
           smp_mb();
   
           queue->read++;
   
           up(&queue->pop);
   
           return header;
   }

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