11fb62fb0SOlivier Houchard /*
21fb62fb0SOlivier Houchard * Copyright 2009-2015 Samy Al Bahra.
31fb62fb0SOlivier Houchard * All rights reserved.
41fb62fb0SOlivier Houchard *
51fb62fb0SOlivier Houchard * Redistribution and use in source and binary forms, with or without
61fb62fb0SOlivier Houchard * modification, are permitted provided that the following conditions
71fb62fb0SOlivier Houchard * are met:
81fb62fb0SOlivier Houchard * 1. Redistributions of source code must retain the above copyright
91fb62fb0SOlivier Houchard * notice, this list of conditions and the following disclaimer.
101fb62fb0SOlivier Houchard * 2. Redistributions in binary form must reproduce the above copyright
111fb62fb0SOlivier Houchard * notice, this list of conditions and the following disclaimer in the
121fb62fb0SOlivier Houchard * documentation and/or other materials provided with the distribution.
131fb62fb0SOlivier Houchard *
141fb62fb0SOlivier Houchard * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
151fb62fb0SOlivier Houchard * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
161fb62fb0SOlivier Houchard * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
171fb62fb0SOlivier Houchard * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
181fb62fb0SOlivier Houchard * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
191fb62fb0SOlivier Houchard * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
201fb62fb0SOlivier Houchard * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
211fb62fb0SOlivier Houchard * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
221fb62fb0SOlivier Houchard * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
231fb62fb0SOlivier Houchard * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
241fb62fb0SOlivier Houchard * SUCH DAMAGE.
251fb62fb0SOlivier Houchard */
261fb62fb0SOlivier Houchard
271fb62fb0SOlivier Houchard #ifndef CK_BACKOFF_H
281fb62fb0SOlivier Houchard #define CK_BACKOFF_H
291fb62fb0SOlivier Houchard
301fb62fb0SOlivier Houchard #include <ck_cc.h>
311fb62fb0SOlivier Houchard #include <ck_pr.h>
321fb62fb0SOlivier Houchard
331fb62fb0SOlivier Houchard #ifndef CK_BACKOFF_CEILING
341fb62fb0SOlivier Houchard #define CK_BACKOFF_CEILING ((1 << 20) - 1)
351fb62fb0SOlivier Houchard #endif
361fb62fb0SOlivier Houchard
371fb62fb0SOlivier Houchard #define CK_BACKOFF_INITIALIZER (1 << 9)
381fb62fb0SOlivier Houchard
391fb62fb0SOlivier Houchard typedef unsigned int ck_backoff_t;
401fb62fb0SOlivier Houchard
411fb62fb0SOlivier Houchard /*
421fb62fb0SOlivier Houchard * This is a exponential back-off implementation.
431fb62fb0SOlivier Houchard */
441fb62fb0SOlivier Houchard CK_CC_INLINE static void
ck_backoff_eb(unsigned int * c)451fb62fb0SOlivier Houchard ck_backoff_eb(unsigned int *c)
461fb62fb0SOlivier Houchard {
471fb62fb0SOlivier Houchard unsigned int i, ceiling;
481fb62fb0SOlivier Houchard
491fb62fb0SOlivier Houchard ceiling = *c;
501fb62fb0SOlivier Houchard for (i = 0; i < ceiling; i++)
511fb62fb0SOlivier Houchard ck_pr_barrier();
521fb62fb0SOlivier Houchard
53*74e9b5f2SOlivier Houchard *c = ceiling << (ceiling < CK_BACKOFF_CEILING);
541fb62fb0SOlivier Houchard return;
551fb62fb0SOlivier Houchard }
561fb62fb0SOlivier Houchard
571fb62fb0SOlivier Houchard #endif /* CK_BACKOFF_H */
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