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1 /* Copyright (C) 2008, 2009 Free Software Foundation, Inc.
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2 Contributed by Jakub Jelinek <jakub@redhat.com>.
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3
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4 This file is part of the GNU OpenMP Library (libgomp).
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5
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6 Libgomp is free software; you can redistribute it and/or modify it
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7 under the terms of the GNU General Public License as published by
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8 the Free Software Foundation; either version 3, or (at your option)
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9 any later version.
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10
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11 Libgomp is distributed in the hope that it will be useful, but WITHOUT ANY
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12 WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
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13 FOR A PARTICULAR PURPOSE. See the GNU General Public License for
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14 more details.
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15
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16 Under Section 7 of GPL version 3, you are granted additional
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17 permissions described in the GCC Runtime Library Exception, version
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18 3.1, as published by the Free Software Foundation.
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19
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20 You should have received a copy of the GNU General Public License and
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21 a copy of the GCC Runtime Library Exception along with this program;
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22 see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
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23 <http://www.gnu.org/licenses/>. */
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24
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25 /* This is a Linux specific implementation of a mutex synchronization
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26 mechanism for libgomp. This type is private to the library. This
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27 implementation uses atomic instructions and the futex syscall. */
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28
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29 #include <endian.h>
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30 #include <limits.h>
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31 #include "wait.h"
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32
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33 void *
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34 gomp_ptrlock_get_slow (gomp_ptrlock_t *ptrlock)
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35 {
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36 int *intptr;
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37 __sync_bool_compare_and_swap (ptrlock, 1, 2);
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38
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39 /* futex works on ints, not pointers.
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40 But a valid work share pointer will be at least
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41 8 byte aligned, so it is safe to assume the low
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42 32-bits of the pointer won't contain values 1 or 2. */
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43 __asm volatile ("" : "=r" (intptr) : "0" (ptrlock));
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44 #if __BYTE_ORDER == __BIG_ENDIAN
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45 if (sizeof (*ptrlock) > sizeof (int))
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46 intptr += (sizeof (*ptrlock) / sizeof (int)) - 1;
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47 #endif
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48 do
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49 do_wait (intptr, 2);
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50 while (*intptr == 2);
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51 __asm volatile ("" : : : "memory");
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52 return *ptrlock;
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53 }
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54
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55 void
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56 gomp_ptrlock_set_slow (gomp_ptrlock_t *ptrlock, void *ptr)
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57 {
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58 int *intptr;
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59
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60 *ptrlock = ptr;
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61 __asm volatile ("" : "=r" (intptr) : "0" (ptrlock));
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62 #if __BYTE_ORDER == __BIG_ENDIAN
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63 if (sizeof (*ptrlock) > sizeof (int))
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64 intptr += (sizeof (*ptrlock) / sizeof (int)) - 1;
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65 #endif
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66 futex_wake (intptr, INT_MAX);
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67 }
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