ck_barrier_centralized.c

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    1 /*
    2  * Copyright 2011-2015 Samy Al Bahra.
    3  * Copyright 2011 David Joseph.
    4  * All rights reserved.
    5  *
    6  * Redistribution and use in source and binary forms, with or without
    7  * modification, are permitted provided that the following conditions
    8  * are met:
    9  * 1. Redistributions of source code must retain the above copyright
   10  *    notice, this list of conditions and the following disclaimer.
   11  * 2. Redistributions in binary form must reproduce the above copyright
   12  *    notice, this list of conditions and the following disclaimer in the
   13  *    documentation and/or other materials provided with the distribution.
   14  *
   15  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
   16  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   17  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   18  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
   19  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   20  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   21  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   22  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   23  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   24  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   25  * SUCH DAMAGE.
   26  */
   27 
   28 #include <ck_barrier.h>
   29 #include <ck_pr.h>
   30 
   31 void
   32 ck_barrier_centralized(struct ck_barrier_centralized *barrier,
   33     struct ck_barrier_centralized_state *state,
   34     unsigned int n_threads)
   35 {
   36         unsigned int sense, value;
   37 
   38         /*
   39          * Every execution context has a sense associated with it.
   40          * This sense is reversed when the barrier is entered. Every
   41          * thread will spin on the global sense until the last thread
   42          * reverses it.
   43          */
   44         sense = state->sense = ~state->sense;
   45         value = ck_pr_faa_uint(&barrier->value, 1);
   46         if (value == n_threads - 1) {
   47                 ck_pr_store_uint(&barrier->value, 0);
   48                 ck_pr_fence_memory();
   49                 ck_pr_store_uint(&barrier->sense, sense);
   50                 return;
   51         }
   52 
   53         ck_pr_fence_atomic_load();
   54         while (sense != ck_pr_load_uint(&barrier->sense))
   55                 ck_pr_stall();
   56 
   57         ck_pr_fence_acquire();
   58         return;
   59 }

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FreeBSD/Linux Kernel Cross Reference sys/contrib/ck/src/ck_barrier_centralized.c

FreeBSD/Linux Kernel Cross Reference
sys/contrib/ck/src/ck_barrier_centralized.c