glibc/sysdeps/unix/sysv/linux/s390/elision-conf.c
Paul Eggert 581c785bf3 Update copyright dates with scripts/update-copyrights
I used these shell commands:

../glibc/scripts/update-copyrights $PWD/../gnulib/build-aux/update-copyright
(cd ../glibc && git commit -am"[this commit message]")

and then ignored the output, which consisted lines saying "FOO: warning:
copyright statement not found" for each of 7061 files FOO.

I then removed trailing white space from math/tgmath.h,
support/tst-support-open-dev-null-range.c, and
sysdeps/x86_64/multiarch/strlen-vec.S, to work around the following
obscure pre-commit check failure diagnostics from Savannah.  I don't
know why I run into these diagnostics whereas others evidently do not.

remote: *** 912-#endif
remote: *** 913:
remote: *** 914-
remote: *** error: lines with trailing whitespace found
...
remote: *** error: sysdeps/unix/sysv/linux/statx_cp.c: trailing lines
2022-01-01 11:40:24 -08:00

124 lines
4.4 KiB
C

/* Lock elision tunable parameters.
Copyright (C) 2014-2022 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, see
<https://www.gnu.org/licenses/>. */
#include <config.h>
#include <pthreadP.h>
#include <elision-conf.h>
#include <unistd.h>
#include <dl-procinfo.h>
#if HAVE_TUNABLES
# define TUNABLE_NAMESPACE elision
#endif
#include <elf/dl-tunables.h>
/* Reasonable initial tuning values, may be revised in the future.
This is a conservative initial value. */
struct elision_config __elision_aconf =
{
/* How often to not attempt to use elision if a transaction aborted
because the lock is already acquired. Expressed in number of lock
acquisition attempts. */
.skip_lock_busy = 3,
/* How often to not attempt to use elision if a transaction aborted due
to reasons other than other threads' memory accesses. Expressed in
number of lock acquisition attempts. */
.skip_lock_internal_abort = 3,
/* How often to not attempt to use elision if a lock used up all retries
without success. Expressed in number of lock acquisition attempts. */
.skip_lock_out_of_tbegin_retries = 3,
/* How often we try using elision if there is chance for the transaction
to finish execution (e.g., it wasn't aborted due to the lock being
already acquired. */
.try_tbegin = 3,
/* Same as SKIP_LOCK_INTERNAL_ABORT but for trylock. */
.skip_trylock_internal_abort = 3,
};
#if HAVE_TUNABLES
static inline void
__always_inline
do_set_elision_enable (int32_t elision_enable)
{
/* Enable elision if it's avaliable in hardware. It's not necessary to check
if __libc_enable_secure isn't enabled since elision_enable will be set
according to the default, which is disabled. */
if (elision_enable == 1)
__pthread_force_elision = (GLRO (dl_hwcap) & HWCAP_S390_TE) ? 1 : 0;
}
/* The pthread->elision_enable tunable is 0 or 1 indicating that elision
should be disabled or enabled respectively. The feature will only be used
if it's supported by the hardware. */
void
TUNABLE_CALLBACK (set_elision_enable) (tunable_val_t *valp)
{
int32_t elision_enable = (int32_t) valp->numval;
do_set_elision_enable (elision_enable);
}
#define TUNABLE_CALLBACK_FNDECL(__name, __type) \
static inline void \
__always_inline \
do_set_elision_ ## __name (__type value) \
{ \
__elision_aconf.__name = value; \
} \
void \
TUNABLE_CALLBACK (set_elision_ ## __name) (tunable_val_t *valp) \
{ \
__type value = (__type) (valp)->numval; \
do_set_elision_ ## __name (value); \
}
TUNABLE_CALLBACK_FNDECL (skip_lock_busy, int32_t);
TUNABLE_CALLBACK_FNDECL (skip_lock_internal_abort, int32_t);
TUNABLE_CALLBACK_FNDECL (skip_lock_out_of_tbegin_retries, int32_t);
TUNABLE_CALLBACK_FNDECL (try_tbegin, int32_t);
TUNABLE_CALLBACK_FNDECL (skip_trylock_internal_abort, int32_t);
#endif
/* Initialize elison. */
void
__lll_elision_init (void)
{
#if HAVE_TUNABLES
/* Elision depends on tunables and must be explicitly turned on by setting
the appropriate tunable on a supported platform. */
TUNABLE_GET (enable, int32_t,
TUNABLE_CALLBACK (set_elision_enable));
TUNABLE_GET (skip_lock_busy, int32_t,
TUNABLE_CALLBACK (set_elision_skip_lock_busy));
TUNABLE_GET (skip_lock_internal_abort, int32_t,
TUNABLE_CALLBACK (set_elision_skip_lock_internal_abort));
TUNABLE_GET (skip_lock_after_retries, int32_t,
TUNABLE_CALLBACK (set_elision_skip_lock_out_of_tbegin_retries));
TUNABLE_GET (tries, int32_t,
TUNABLE_CALLBACK (set_elision_try_tbegin));
TUNABLE_GET (skip_trylock_internal_abort, int32_t,
TUNABLE_CALLBACK (set_elision_skip_trylock_internal_abort));
#endif
if (!__pthread_force_elision)
__elision_aconf.try_tbegin = 0; /* Disable elision on rwlocks. */
}