pt-machine.h

它通过提供glibc兼容使得应用程序移植到较小的c 库时相当得容易. 它能够应用到带虚拟存储的Linux和uClinux上.在大多数带MMU部件的平台上为使它更加紧凑,它也能够编译成共享库.uClib

/* Machine-dependent pthreads configuration and inline functions.
   Alpha version.
   Copyright (C) 1996, 1997, 1998, 2000, 2002 Free Software Foundation, Inc.
   This file is part of the GNU C Library.
   Contributed by Richard Henderson <[e-mail]>.

   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,
   write to the Free Software Foundation, Inc.,  59 Temple Place - Suite 330,
   Boston, MA 02111-1307, USA.  */

#ifndef _PT_MACHINE_H
#define _PT_MACHINE_H   1

#ifndef PT_EI
# define PT_EI extern inline
#endif

#ifdef __linux__
# include <asm/pal.h>
#else
# include <machine/pal.h>
#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  stack_pointer
register char *stack_pointer __asm__("$30");


/* Memory barrier; default is to do nothing */
#define MEMORY_BARRIER() __asm__ __volatile__("mb" : : : "memory")
/* Write barrier.  */
#define WRITE_MEMORY_BARRIER() __asm__ __volatile__("wmb" : : : "memory")


/* Spinlock implementation; required.  */
PT_EI long int
testandset (int *spinlock)
{
  long int ret, temp;

  __asm__ __volatile__(
	"/* Inline spinlock test & set */\n"
	"1:\t"
	"ldl_l %0,%3\n\t"
	"bne %0,2f\n\t"
	"or $31,1,%1\n\t"
	"stl_c %1,%2\n\t"
	"beq %1,1b\n"
	"2:\tmb\n"
	"/* End spinlock test & set */"
	: "=&r"(ret), "=&r"(temp), "=m"(*spinlock)
	: "m"(*spinlock)
        : "memory");

  return ret;
}


/* Begin allocating thread stacks at this address.  Default is to allocate
   them just below the initial program stack.  */
#define THREAD_STACK_START_ADDRESS  0x40000000000


/* Return the thread descriptor for the current thread.  */
#define THREAD_SELF \
({									      \
  register pthread_descr __self __asm__("$0");				      \
  __asm__ ("call_pal %1" : "=r"(__self) : "i"(PAL_rduniq));		      \
  __self;								      \
})

/* Initialize the thread-unique value.  */
#define INIT_THREAD_SELF(descr, nr) \
{									      \
  register pthread_descr __self __asm__("$16") = (descr);		      \
  __asm__ __volatile__ ("call_pal %1" : : "r"(__self), "i"(PAL_wruniq));      \
}


/* Compare-and-swap for semaphores. */

#define HAS_COMPARE_AND_SWAP
PT_EI int
__compare_and_swap (long int *p, long int oldval, long int newval)
{
  long int ret;

  __asm__ __volatile__ (
	"/* Inline compare & swap */\n"
	"1:\t"
	"ldq_l %0,%4\n\t"
	"cmpeq %0,%2,%0\n\t"
	"beq %0,2f\n\t"
	"mov %3,%0\n\t"
	"stq_c %0,%1\n\t"
	"beq %0,1b\n\t"
	"2:\tmb\n"
	"/* End compare & swap */"
	: "=&r"(ret), "=m"(*p)
	: "r"(oldval), "r"(newval), "m"(*p)
        : "memory");

  return ret;
}

/* We want the OS to assign stack addresses.  */
#define FLOATING_STACKS 1

/* Maximum size of the stack if the rlimit is unlimited.  */
#define ARCH_STACK_MAX_SIZE     32*1024*1024

#endif /* pt-machine.h */