| 1 | /*
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| 2 | * Copyright (c) 2018 CZ.NIC, z.s.p.o.
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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 | #include <atomic.h>
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| 30 |
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| 31 | #ifdef PLATFORM_arm32
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| 32 |
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| 33 | /*
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| 34 | * Older ARMs don't have atomic instructions, so we need to define a bunch
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| 35 | * of symbols for GCC to use.
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| 36 | */
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| 37 |
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| 38 | unsigned __sync_add_and_fetch_4(volatile void *vptr, unsigned val)
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| 39 | {
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| 40 | return atomic_add((atomic_t *)vptr, val);
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| 41 | }
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| 42 |
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| 43 | unsigned __sync_sub_and_fetch_4(volatile void *vptr, unsigned val)
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| 44 | {
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| 45 | return atomic_add((atomic_t *)vptr, -(atomic_signed_t)val);
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| 46 | }
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| 47 |
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| 48 | bool __sync_bool_compare_and_swap_4(volatile void *ptr, unsigned old_val, unsigned new_val)
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| 49 | {
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| 50 | return cas((atomic_t *)ptr, old_val, new_val);
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| 51 | }
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| 52 |
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| 53 | unsigned __sync_val_compare_and_swap_4(volatile void *ptr, unsigned old_val, unsigned new_val)
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| 54 | {
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| 55 | while (true) {
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| 56 | if (__sync_bool_compare_and_swap_4(ptr, old_val, new_val)) {
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| 57 | return old_val;
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| 58 | }
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| 59 |
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| 60 | unsigned current = *(volatile unsigned *)ptr;
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| 61 | if (current != old_val)
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| 62 | return current;
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| 63 |
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| 64 | /* If the current value is the same as old_val, retry. */
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| 65 | }
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| 66 | }
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| 67 |
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| 68 | #endif
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