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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 | /* Machine-dependent pthreads configuration and inline functions. i386 version. Copyright (C) 1996-2001, 2002, 2003 Free Software Foundation, Inc. This file is part of the GNU C Library. Contributed by Richard Henderson <rth@tamu.edu>. The GNU C Library is free software; you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation; either version 2.1 of the License, or (at your option) any later version. The GNU C Library is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more details. You should have received a copy of the GNU Lesser General Public License along with the GNU C Library; see the file COPYING.LIB. If not, see <http://www.gnu.org/licenses/>. */ #ifndef _PT_MACHINE_H #define _PT_MACHINE_H 1 #include <features.h> #ifndef __ASSEMBLER__ #ifndef PT_EI # define PT_EI __extern_always_inline __attribute__((visibility("hidden"))) #endif extern long int testandset (int *spinlock); extern int __compare_and_swap (long int *p, long int oldval, long int newval); /* Get some notion of the current stack. Need not be exactly the top of the stack, just something somewhere in the current frame. */ #define CURRENT_STACK_FRAME __builtin_frame_address (0) /* See if we can optimize for newer cpus... */ #if defined __GNUC__ && __GNUC__ >= 2 && \ (defined __i486__ || defined __pentium__ || defined __pentiumpro__ || defined __pentium4__ || \ defined __athlon__ || defined __k8__) /* Spinlock implementation; required. */ PT_EI long int testandset (int *spinlock) { long int ret; __asm__ __volatile__ ( "xchgl %0, %1" : "=r" (ret), "=m" (*spinlock) : "0" (1), "m" (*spinlock) : "memory"); return ret; } /* Compare-and-swap for semaphores. It's always available on i686. */ #define HAS_COMPARE_AND_SWAP PT_EI int __compare_and_swap (long int *p, long int oldval, long int newval) { char ret; long int readval; __asm__ __volatile__ ("lock; cmpxchgl %3, %1; sete %0" : "=q" (ret), "=m" (*p), "=a" (readval) : "r" (newval), "m" (*p), "a" (oldval) : "memory"); return ret; } #if defined(__ASSUME_LDT_WORKS) && __ASSUME_LDT_WORKS > 0 #include "useldt.h" #endif /* The P4 and above really want some help to prevent overheating. */ #define BUSY_WAIT_NOP __asm__ ("rep; nop") #else /* Generic i386 implementation */ extern int compare_and_swap_is_available (void); /* Spinlock implementation; required. */ PT_EI long int testandset (int *spinlock) { long int ret; __asm__ __volatile__( "xchgl %0, %1" : "=r"(ret), "=m"(*spinlock) : "0"(1), "m"(*spinlock) : "memory"); return ret; } /* Compare-and-swap for semaphores. Available on the 486 and above, but not on the 386. We test dynamically whether it's available or not. */ #define HAS_COMPARE_AND_SWAP #define TEST_FOR_COMPARE_AND_SWAP PT_EI int __compare_and_swap (long int *p, long int oldval, long int newval) { char ret; long int readval; __asm__ __volatile__ ("lock; cmpxchgl %3, %1; sete %0" : "=q" (ret), "=m" (*p), "=a" (readval) : "r" (newval), "m" (*p), "a" (oldval) : "memory"); return ret; } PT_EI int compare_and_swap_is_available (void) { int changed; int oldflags; /* get EFLAGS */ __asm__ __volatile__ ("pushfl; popl %0" : "=r" (oldflags) : ); /* Flip AC bit in EFLAGS. */ __asm__ __volatile__ ("pushl %0; popfl" : : "r" (oldflags ^ 0x40000) : "cc"); /* reread EFLAGS */ __asm__ __volatile__ ("pushfl; popl %0" : "=r" (changed) : ); /* See if bit changed. */ changed = (changed ^ oldflags) & 0x40000; /* Restore EFLAGS. */ __asm__ __volatile__ ("pushl %0; popfl" : : "r" (oldflags) : "cc"); /* If the AC flag did not change, it's a 386 and it lacks cmpxchg. Otherwise, it's a 486 or above and it has cmpxchg. */ return changed != 0; } #endif /* Generic i386 implementation */ #endif /* __ASSEMBLER__ */ #endif /* pt-machine.h */ |