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1 | /*****************************************************************************\ |
2 | * Copyright (C) 2007-2010 Lawrence Livermore National Security, LLC. | |
3 | * Copyright (C) 2007 The Regents of the University of California. | |
4 | * Produced at Lawrence Livermore National Laboratory (cf, DISCLAIMER). | |
5 | * Written by Brian Behlendorf <behlendorf1@llnl.gov>. | |
715f6251 | 6 | * UCRL-CODE-235197 |
7 | * | |
716154c5 BB |
8 | * This file is part of the SPL, Solaris Porting Layer. |
9 | * For details, see <http://github.com/behlendorf/spl/>. | |
10 | * | |
11 | * The SPL is free software; you can redistribute it and/or modify it | |
12 | * under the terms of the GNU General Public License as published by the | |
13 | * Free Software Foundation; either version 2 of the License, or (at your | |
14 | * option) any later version. | |
715f6251 | 15 | * |
716154c5 | 16 | * The SPL is distributed in the hope that it will be useful, but WITHOUT |
715f6251 | 17 | * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
18 | * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License | |
19 | * for more details. | |
20 | * | |
21 | * You should have received a copy of the GNU General Public License along | |
716154c5 BB |
22 | * with the SPL. If not, see <http://www.gnu.org/licenses/>. |
23 | ***************************************************************************** | |
24 | * Solaris Porting Layer (SPL) Mutex Implementation. | |
25 | \*****************************************************************************/ | |
715f6251 | 26 | |
9ab1ac14 | 27 | #include <sys/mutex.h> |
28 | ||
29 | #ifdef DEBUG_SUBSYSTEM | |
30 | #undef DEBUG_SUBSYSTEM | |
31 | #endif | |
32 | ||
33 | #define DEBUG_SUBSYSTEM S_MUTEX | |
34 | ||
4d54fdee BB |
35 | /* |
36 | * While a standard mutex implementation has been available in the kernel | |
37 | * for quite some time. It was not until 2.6.29 and latter kernels that | |
38 | * adaptive mutexs were embraced and integrated with the scheduler. This | |
39 | * brought a significant performance improvement, but just as importantly | |
40 | * it added a lock owner to the generic mutex outside CONFIG_DEBUG_MUTEXES | |
41 | * builds. This is critical for correctly supporting the mutex_owner() | |
42 | * Solaris primitive. When the owner is available we use a pure Linux | |
43 | * mutex implementation. When the owner is not available we still use | |
44 | * Linux mutexs as a base but also reserve space for an owner field right | |
45 | * after the mutex structure. | |
9ab1ac14 | 46 | * |
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47 | * In the case when HAVE_MUTEX_OWNER is not defined your code may |
48 | * still me able to leverage adaptive mutexs. As long as the task_curr() | |
49 | * symbol is exported this code will provide a poor mans adaptive mutex | |
50 | * implementation. However, this is not required and if the symbol is | |
51 | * unavailable we provide a standard mutex. | |
9ab1ac14 | 52 | */ |
53 | ||
38b5ff4d | 54 | #if !defined(HAVE_MUTEX_OWNER) || !defined(CONFIG_SMP) || defined(CONFIG_DEBUG_MUTEXES) |
4d54fdee BB |
55 | #ifdef HAVE_TASK_CURR |
56 | /* | |
57 | * mutex_spin_max = { 0, -1, 1-MAX_INT } | |
58 | * 0: Never spin when trying to acquire lock | |
59 | * -1: Spin until acquired or holder yields without dropping lock | |
9ab1ac14 | 60 | * 1-MAX_INT: Spin for N attempts before sleeping for lock |
61 | */ | |
56f92453 | 62 | int mutex_spin_max = 0; |
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63 | module_param(mutex_spin_max, int, 0644); |
64 | MODULE_PARM_DESC(mutex_spin_max, "Spin a maximum of N times to acquire lock"); | |
9ab1ac14 | 65 | |
66 | int | |
4d54fdee | 67 | spl_mutex_spin_max(void) |
9ab1ac14 | 68 | { |
4d54fdee | 69 | return mutex_spin_max; |
9ab1ac14 | 70 | } |
4d54fdee | 71 | EXPORT_SYMBOL(spl_mutex_spin_max); |
9ab1ac14 | 72 | |
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73 | #endif /* HAVE_TASK_CURR */ |
74 | #endif /* !HAVE_MUTEX_OWNER */ | |
9ab1ac14 | 75 | |
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76 | int spl_mutex_init(void) { return 0; } |
77 | void spl_mutex_fini(void) { } |