glibc/nptl/lowlevellock.c
Florian Weimer 5a664d7ae8 nptl: Move elision implementations into libc
The elision interfaces are closely aligned between the targets that
implement them, so declare them in the generic <lowlevellock.h>
file.

Empty .c stubs are provided, so that fewer makefile updates
under sysdeps are needed.  Also simplify initialization via
__libc_early_init.

The symbols __lll_clocklock_elision, __lll_lock_elision,
__lll_trylock_elision, __lll_unlock_elision, __pthread_force_elision
move into libc.  For the time being, non-hidden references are used
from libpthread to access them, but once that part of libpthread
is moved into libc, hidden symbols will be used again.  (Hidden
references seem desirable to reduce the likelihood of transactions
aborts.)
2021-02-23 14:59:34 +01:00

59 lines
1.8 KiB
C

/* low level locking for pthread library. Generic futex-using version.
Copyright (C) 2003-2021 Free Software Foundation, Inc.
This file is part of the GNU C Library.
Contributed by Paul Mackerras <paulus@au.ibm.com>, 2003.
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
<https://www.gnu.org/licenses/>. */
#include <sysdep.h>
#include <futex-internal.h>
#include <atomic.h>
#include <stap-probe.h>
void
__lll_lock_wait_private (int *futex)
{
if (atomic_load_relaxed (futex) == 2)
goto futex;
while (atomic_exchange_acquire (futex, 2) != 0)
{
futex:
LIBC_PROBE (lll_lock_wait_private, 1, futex);
futex_wait ((unsigned int *) futex, 2, LLL_PRIVATE); /* Wait if *futex == 2. */
}
}
libc_hidden_def (__lll_lock_wait_private)
void
__lll_lock_wait (int *futex, int private)
{
if (atomic_load_relaxed (futex) == 2)
goto futex;
while (atomic_exchange_acquire (futex, 2) != 0)
{
futex:
LIBC_PROBE (lll_lock_wait, 1, futex);
futex_wait ((unsigned int *) futex, 2, private); /* Wait if *futex == 2. */
}
}
libc_hidden_def (__lll_lock_wait)
#if ENABLE_ELISION_SUPPORT
int __pthread_force_elision __attribute__ ((nocommon));
libc_hidden_data_def (__pthread_force_elision)
#endif