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99 lines
2.7 KiB
C
99 lines
2.7 KiB
C
/* Machine-dependent pthreads configuration and inline functions.
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i386 version.
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Copyright (C) 1996, 1997, 1998 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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Contributed by Richard Henderson <rth@tamu.edu>.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Library General Public License as
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published by the Free Software Foundation; either version 2 of the
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License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Library General Public License for more details.
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You should have received a copy of the GNU Library General Public
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License along with the GNU C Library; see the file COPYING.LIB. If not,
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write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
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Boston, MA 02111-1307, USA. */
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#ifndef PT_EI
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# define PT_EI extern inline
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#endif
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/* Spinlock implementation; required. */
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PT_EI int
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testandset (int *spinlock)
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{
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int ret;
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__asm__ __volatile__(
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"xchgl %0, %1"
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: "=r"(ret), "=m"(*spinlock)
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: "0"(1), "m"(*spinlock)
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: "memory");
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return ret;
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}
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/* Get some notion of the current stack. Need not be exactly the top
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of the stack, just something somewhere in the current frame. */
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#define CURRENT_STACK_FRAME stack_pointer
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register char * stack_pointer __asm__ ("%esp");
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/* Compare-and-swap for semaphores.
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Available on the 486 and above, but not on the 386.
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We test dynamically whether it's available or not. */
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#define HAS_COMPARE_AND_SWAP
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#define TEST_FOR_COMPARE_AND_SWAP
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PT_EI int
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__compare_and_swap (long int *p, long int oldval, long int newval)
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{
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char ret;
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long int readval;
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__asm__ __volatile__ ("lock; cmpxchgl %3, %1; sete %0"
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: "=q" (ret), "=m" (*p), "=a" (readval)
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: "r" (newval), "m" (*p), "a" (oldval));
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return ret;
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}
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PT_EI int
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get_eflags (void)
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{
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int res;
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__asm__ __volatile__ ("pushfl; popl %0" : "=r" (res) : );
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return res;
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}
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PT_EI void
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set_eflags (int newflags)
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{
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__asm__ __volatile__ ("pushl %0; popfl" : : "r" (newflags) : "cc");
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}
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PT_EI int
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compare_and_swap_is_available (void)
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{
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int oldflags = get_eflags ();
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int changed;
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/* Flip AC bit in EFLAGS. */
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set_eflags (oldflags ^ 0x40000);
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/* See if bit changed. */
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changed = (get_eflags () ^ oldflags) & 0x40000;
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/* Restore EFLAGS. */
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set_eflags (oldflags);
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/* If the AC flag did not change, it's a 386 and it lacks cmpxchg.
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Otherwise, it's a 486 or above and it has cmpxchg. */
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return changed != 0;
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}
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