| 1 | /*
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| 2 | * Copyright (c) 2008 Jakub Jermar
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| 3 | * All rights reserved.
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| 4 | *
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| 5 | * Redistribution and use in source and binary forms, with or without
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| 6 | * modification, are permitted provided that the following conditions
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| 7 | * are met:
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| 8 | *
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| 9 | * - Redistributions of source code must retain the above copyright
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| 10 | * notice, this list of conditions and the following disclaimer.
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| 11 | * - Redistributions in binary form must reproduce the above copyright
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| 12 | * notice, this list of conditions and the following disclaimer in the
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| 13 | * documentation and/or other materials provided with the distribution.
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| 14 | * - The name of the author may not be used to endorse or promote products
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| 15 | * derived from this software without specific prior written permission.
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| 16 | *
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| 17 | * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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| 18 | * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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| 19 | * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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| 20 | * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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| 21 | * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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| 22 | * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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| 23 | * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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| 24 | * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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| 25 | * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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| 26 | * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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| 27 | */
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| 28 |
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| 29 | /** @addtogroup libc
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| 30 | * @{
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| 31 | */
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| 32 | /** @file
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| 33 | */
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| 34 |
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| 35 | #include <futex.h>
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| 36 | #include <atomic.h>
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| 37 | #include <libc.h>
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| 38 | #include <sys/types.h>
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| 39 |
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| 40 | /** Initialize futex counter.
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| 41 | *
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| 42 | * @param futex Futex.
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| 43 | * @param val Initialization value.
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| 44 | */
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| 45 | void futex_initialize(futex_t *futex, int val)
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| 46 | {
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| 47 | atomic_set(futex, val);
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| 48 | }
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| 49 |
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| 50 | /** Try to down the futex.
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| 51 | *
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| 52 | * @param futex Futex.
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| 53 | * @return Non-zero if the futex was acquired.
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| 54 | * @return Zero if the futex was not acquired.
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| 55 | */
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| 56 | int futex_trydown(futex_t *futex)
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| 57 | {
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| 58 | return cas(futex, 1, 0);
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| 59 | }
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| 60 |
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| 61 | /** Down the futex.
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| 62 | *
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| 63 | * @param futex Futex.
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| 64 | * @return ENOENT if there is no such virtual address.
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| 65 | * @return Zero in the uncontended case.
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| 66 | * @return Otherwise one of ESYNCH_OK_ATOMIC or ESYNCH_OK_BLOCKED.
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| 67 | */
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| 68 | int futex_down(futex_t *futex)
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| 69 | {
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| 70 | if (atomic_predec(futex) < 0)
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| 71 | return __SYSCALL1(SYS_FUTEX_SLEEP, (sysarg_t) &futex->count);
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| 72 |
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| 73 | return 0;
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| 74 | }
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| 75 |
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| 76 | /** Up the futex.
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| 77 | *
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| 78 | * @param futex Futex.
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| 79 | * @return ENOENT if there is no such virtual address.
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| 80 | * @return Zero in the uncontended case.
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| 81 | */
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| 82 | int futex_up(futex_t *futex)
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| 83 | {
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| 84 | if (atomic_postinc(futex) < 0)
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| 85 | return __SYSCALL1(SYS_FUTEX_WAKEUP, (sysarg_t) &futex->count);
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| 86 |
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| 87 | return 0;
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| 88 | }
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| 89 |
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| 90 | /** @}
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| 91 | */
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