1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
|
/* Lock elision tunable parameters.
Copyright (C) 2014-2019 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,
};
/* Force elision for all new locks. This is used to decide whether existing
DEFAULT locks should be automatically upgraded to elision in
pthread_mutex_lock(). Disabled for suid programs. Only used when elision
is available. */
int __pthread_force_elision attribute_hidden = 0;
#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. */
static void
elision_init (int argc __attribute__ ((unused)),
char **argv __attribute__ ((unused)),
char **environ)
{
#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. */
}
#ifdef SHARED
# define INIT_SECTION ".init_array"
# define MAYBE_CONST
#else
# define INIT_SECTION ".preinit_array"
# define MAYBE_CONST const
#endif
void (*MAYBE_CONST __pthread_init_array []) (int, char **, char **)
__attribute__ ((section (INIT_SECTION), aligned (sizeof (void *)))) =
{
&elision_init
};
|
