From c68d0fa2d88fc2134a38d99e7e944828384a7671 Mon Sep 17 00:00:00 2001 From: Austin Foxley Date: Sat, 17 Oct 2009 12:26:24 -0700 Subject: libpthread/nptl: core of the "Native Posix Threading Library" for uClibc targetting arm,sh,i386,mips,sparc for now Signed-off-by: Austin Foxley --- .../sysdeps/unix/sysv/linux/alpha/pthread_once.c | 96 ++++++++++++++++++++++ 1 file changed, 96 insertions(+) create mode 100644 libpthread/nptl/sysdeps/unix/sysv/linux/alpha/pthread_once.c (limited to 'libpthread/nptl/sysdeps/unix/sysv/linux/alpha/pthread_once.c') diff --git a/libpthread/nptl/sysdeps/unix/sysv/linux/alpha/pthread_once.c b/libpthread/nptl/sysdeps/unix/sysv/linux/alpha/pthread_once.c new file mode 100644 index 000000000..79a3c47ae --- /dev/null +++ b/libpthread/nptl/sysdeps/unix/sysv/linux/alpha/pthread_once.c @@ -0,0 +1,96 @@ +/* Copyright (C) 2003, 2004 Free Software Foundation, Inc. + This file is part of the GNU C Library. + + 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; if not, write to the Free + Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA + 02111-1307 USA. */ + +#include "pthreadP.h" +#include + + +unsigned long int __fork_generation attribute_hidden; + +static void +clear_once_control (void *arg) +{ + pthread_once_t *once_control = (pthread_once_t *) arg; + + *once_control = 0; + lll_futex_wake (once_control, INT_MAX); +} + +int +__pthread_once (pthread_once_t *once_control, void (*init_routine) (void)) +{ + for (;;) + { + int oldval; + int newval; + int tmp; + + /* Pseudo code: + newval = __fork_generation | 1; + oldval = *once_control; + if ((oldval & 2) == 0) + *once_control = newval; + Do this atomically. + */ + newval = __fork_generation | 1; + __asm __volatile ( + "1: ldl_l %0, %2\n" + " and %0, 2, %1\n" + " bne %1, 2f\n" + " mov %3, %1\n" + " stl_c %1, %2\n" + " beq %1, 1b\n" + "2: mb" + : "=&r" (oldval), "=&r" (tmp), "=m" (*once_control) + : "r" (newval), "m" (*once_control)); + + /* Check if the initializer has already been done. */ + if ((oldval & 2) != 0) + return 0; + + /* Check if another thread already runs the initializer. */ + if ((oldval & 1) == 0) + break; + + /* Check whether the initializer execution was interrupted by a fork. */ + if (oldval != newval) + break; + + /* Same generation, some other thread was faster. Wait. */ + lll_futex_wait (once_control, oldval); + } + + /* This thread is the first here. Do the initialization. + Register a cleanup handler so that in case the thread gets + interrupted the initialization can be restarted. */ + pthread_cleanup_push (clear_once_control, once_control); + + init_routine (); + + pthread_cleanup_pop (0); + + /* Add one to *once_control to take the bottom 2 bits from 01 to 10. */ + atomic_increment (once_control); + + /* Wake up all other threads. */ + lll_futex_wake (once_control, INT_MAX); + + return 0; +} +weak_alias (__pthread_once, pthread_once) +strong_alias (__pthread_once, __pthread_once_internal) -- cgit v1.2.3