ck_backoff.h

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    1 /*
    2  * Copyright 2009-2015 Samy Al Bahra.
    3  * All rights reserved.
    4  *
    5  * Redistribution and use in source and binary forms, with or without
    6  * modification, are permitted provided that the following conditions
    7  * are met:
    8  * 1. Redistributions of source code must retain the above copyright
    9  *    notice, this list of conditions and the following disclaimer.
   10  * 2. Redistributions in binary form must reproduce the above copyright
   11  *    notice, this list of conditions and the following disclaimer in the
   12  *    documentation and/or other materials provided with the distribution.
   13  *
   14  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
   15  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   16  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   17  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
   18  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   19  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   20  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   21  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   22  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   23  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   24  * SUCH DAMAGE.
   25  */
   26 
   27 #ifndef CK_BACKOFF_H
   28 #define CK_BACKOFF_H
   29 
   30 #include <ck_cc.h>
   31 #include <ck_pr.h>
   32 
   33 #ifndef CK_BACKOFF_CEILING
   34 #define CK_BACKOFF_CEILING ((1 << 20) - 1)
   35 #endif
   36 
   37 #define CK_BACKOFF_INITIALIZER (1 << 9)
   38 
   39 typedef unsigned int ck_backoff_t;
   40 
   41 /*
   42  * This is a exponential back-off implementation.
   43  */
   44 CK_CC_INLINE static void
   45 ck_backoff_eb(unsigned int *c)
   46 {
   47         unsigned int i, ceiling;
   48 
   49         ceiling = *c;
   50         for (i = 0; i < ceiling; i++)
   51                 ck_pr_barrier();
   52 
   53         *c = ceiling << (ceiling < CK_BACKOFF_CEILING);
   54         return;
   55 }
   56 
   57 #endif /* CK_BACKOFF_H */

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FreeBSD/Linux Kernel Cross Reference sys/contrib/ck/include/ck_backoff.h

FreeBSD/Linux Kernel Cross Reference
sys/contrib/ck/include/ck_backoff.h