mirror of
https://sourceware.org/git/glibc.git
synced 2024-12-30 14:31:14 +00:00
84 lines
2.3 KiB
C
84 lines
2.3 KiB
C
/* Low level locking macros used in NPTL implementation. Stub version.
|
|
Copyright (C) 2002-2013 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, see
|
|
<http://www.gnu.org/licenses/>. */
|
|
|
|
#include <atomic.h>
|
|
|
|
|
|
/* 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,
|
|
// XYZ check mutex flag
|
|
LLL_SHARED);
|
|
}
|
|
}
|
|
|
|
|
|
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 (mutex, 0x80000000))
|
|
return;
|
|
|
|
/* There are other threads waiting for this mutex, wake one of them
|
|
up. */
|
|
lll_futex_wake (mutex, 1,
|
|
// XYZ check mutex flag
|
|
LLL_SHARED);
|
|
}
|
|
|
|
|
|
#define lll_mutex_lock(futex) __generic_mutex_lock (&(futex))
|
|
#define lll_mutex_unlock(futex) __generic_mutex_unlock (&(futex))
|