diff options
author | Ulrich Drepper <drepper@redhat.com> | 2004-12-22 20:10:10 +0000 |
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committer | Ulrich Drepper <drepper@redhat.com> | 2004-12-22 20:10:10 +0000 |
commit | a334319f6530564d22e775935d9c91663623a1b4 (patch) | |
tree | b5877475619e4c938e98757d518bb1e9cbead751 /nptl/sysdeps/generic/lowlevellock.h | |
parent | 0ecb606cb6cf65de1d9fc8a919bceb4be476c602 (diff) |
(CFLAGS-tst-align.c): Add -mpreferred-stack-boundary=4.
Diffstat (limited to 'nptl/sysdeps/generic/lowlevellock.h')
-rw-r--r-- | nptl/sysdeps/generic/lowlevellock.h | 89 |
1 files changed, 89 insertions, 0 deletions
diff --git a/nptl/sysdeps/generic/lowlevellock.h b/nptl/sysdeps/generic/lowlevellock.h new file mode 100644 index 0000000000..9cffca83e6 --- /dev/null +++ b/nptl/sysdeps/generic/lowlevellock.h @@ -0,0 +1,89 @@ +/* Copyright (C) 2002 Free Software Foundation, Inc. + This file is part of the GNU C Library. + Contributed by Ulrich Drepper <drepper@redhat.com>, 2002. + + 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 <atomic.h> + + +/* Implement generic mutex. Basic futex syscall support is required: + + lll_futex_wait(futex, value) - call sys_futex with FUTEX_WAIT + and third parameter VALUE + + lll_futex_wake(futex, value) - call sys_futex with FUTEX_WAKE + and third parameter VALUE +*/ + + +/* Mutex lock counter: + bit 31 clear means unlocked; + bit 31 set means locked. + + All code that looks at bit 31 first increases the 'number of + interested threads' usage counter, which is in bits 0-30. + + All negative mutex values indicate that the mutex is still locked. */ + + +static inline void +__generic_mutex_lock (int *mutex) +{ + unsigned int v; + + /* Bit 31 was clear, we got the mutex. (this is the fastpath). */ + if (atomic_bit_test_set (mutex, 31) == 0) + return; + + atomic_increment (mutex); + + while (1) + { + if (atomic_bit_test_set (mutex, 31) == 0) + { + atomic_decrement (mutex); + return; + } + + /* We have to wait now. First make sure the futex value we are + monitoring is truly negative (i.e. locked). */ + v = *mutex; + if (v >= 0) + continue; + + lll_futex_wait (mutex, v); + } +} + + +static inline void +__generic_mutex_unlock (int *mutex) +{ + /* Adding 0x80000000 to the counter results in 0 if and only if + there are not other interested threads - we can return (this is + the fastpath). */ + if (atomic_add_zero (0x80000000, mutex)) + return; + + /* There are other threads waiting for this mutex, wake one of them + up. */ + lll_futex_wake (mutex, 1); +} + + +#define lll_mutex_lock(futex) __generic_mutex_lock (&(futex)) +#define lll_mutex_unlock(futex) __generic_mutex_unlock (&(futex)) |