1 | /* elision-conf.c: Lock elision tunable parameters. |
2 | Copyright (C) 2013-2016 Free Software Foundation, Inc. |
3 | This file is part of the GNU C Library. |
4 | |
5 | The GNU C Library is free software; you can redistribute it and/or |
6 | modify it under the terms of the GNU Lesser General Public |
7 | License as published by the Free Software Foundation; either |
8 | version 2.1 of the License, or (at your option) any later version. |
9 | |
10 | The GNU C Library is distributed in the hope that it will be useful, |
11 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
12 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
13 | Lesser General Public License for more details. |
14 | |
15 | You should have received a copy of the GNU Lesser General Public |
16 | License along with the GNU C Library; if not, see |
17 | <http://www.gnu.org/licenses/>. */ |
18 | |
19 | #include "config.h" |
20 | #include <pthreadP.h> |
21 | #include <init-arch.h> |
22 | #include <elision-conf.h> |
23 | #include <unistd.h> |
24 | |
25 | /* Reasonable initial tuning values, may be revised in the future. |
26 | This is a conservative initial value. */ |
27 | |
28 | struct elision_config __elision_aconf = |
29 | { |
30 | /* How often to not attempt to use elision if a transaction aborted |
31 | because the lock is already acquired. Expressed in number of lock |
32 | acquisition attempts. */ |
33 | .skip_lock_busy = 3, |
34 | /* How often to not attempt to use elision if a transaction aborted due |
35 | to reasons other than other threads' memory accesses. Expressed in |
36 | number of lock acquisition attempts. */ |
37 | .skip_lock_internal_abort = 3, |
38 | /* How often we retry using elision if there is chance for the transaction |
39 | to finish execution (e.g., it wasn't aborted due to the lock being |
40 | already acquired. */ |
41 | .retry_try_xbegin = 3, |
42 | /* Same as SKIP_LOCK_INTERNAL_ABORT but for trylock. */ |
43 | .skip_trylock_internal_abort = 3, |
44 | }; |
45 | |
46 | /* Set when the CPU supports elision. When false elision is never attempted. |
47 | */ |
48 | |
49 | int __elision_available attribute_hidden; |
50 | |
51 | /* Force elision for all new locks. This is used to decide whether existing |
52 | DEFAULT locks should be automatically upgraded to elision in |
53 | pthread_mutex_lock(). Disabled for suid programs. Only used when elision |
54 | is available. */ |
55 | |
56 | int __pthread_force_elision attribute_hidden; |
57 | |
58 | /* Initialize elison. */ |
59 | |
60 | static void |
61 | elision_init (int argc __attribute__ ((unused)), |
62 | char **argv __attribute__ ((unused)), |
63 | char **environ) |
64 | { |
65 | __elision_available = HAS_CPU_FEATURE (RTM); |
66 | #ifdef ENABLE_LOCK_ELISION |
67 | __pthread_force_elision = __libc_enable_secure ? 0 : __elision_available; |
68 | #endif |
69 | if (!HAS_CPU_FEATURE (RTM)) |
70 | __elision_aconf.retry_try_xbegin = 0; /* Disable elision on rwlocks */ |
71 | } |
72 | |
73 | #ifdef SHARED |
74 | # define INIT_SECTION ".init_array" |
75 | #else |
76 | # define INIT_SECTION ".preinit_array" |
77 | #endif |
78 | |
79 | void (*const __pthread_init_array []) (int, char **, char **) |
80 | __attribute__ ((section (INIT_SECTION), aligned (sizeof (void *)))) = |
81 | { |
82 | &elision_init |
83 | }; |
84 | |