1 /* $OpenBSD: kern_lock.c,v 1.46 2014/09/14 14:17:25 jsg Exp $ */ 2 3 /* 4 * Copyright (c) 1995 5 * The Regents of the University of California. All rights reserved. 6 * 7 * This code contains ideas from software contributed to Berkeley by 8 * Avadis Tevanian, Jr., Michael Wayne Young, and the Mach Operating 9 * System project at Carnegie-Mellon University. 10 * 11 * Redistribution and use in source and binary forms, with or without 12 * modification, are permitted provided that the following conditions 13 * are met: 14 * 1. Redistributions of source code must retain the above copyright 15 * notice, this list of conditions and the following disclaimer. 16 * 2. Redistributions in binary form must reproduce the above copyright 17 * notice, this list of conditions and the following disclaimer in the 18 * documentation and/or other materials provided with the distribution. 19 * 3. Neither the name of the University nor the names of its contributors 20 * may be used to endorse or promote products derived from this software 21 * without specific prior written permission. 22 * 23 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 24 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 25 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 26 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 27 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 28 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 29 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 30 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 31 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 32 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 33 * SUCH DAMAGE. 34 * 35 * @(#)kern_lock.c 8.18 (Berkeley) 5/21/95 36 */ 37 38 #include <sys/param.h> 39 #include <sys/lock.h> 40 #include <sys/systm.h> 41 #include <sys/sched.h> 42 43 #ifdef MP_LOCKDEBUG 44 /* CPU-dependent timing, this needs to be settable from ddb. */ 45 int __mp_lock_spinout = 200000000; 46 #endif 47 48 /* 49 * Initialize a lock; required before use. 50 */ 51 void 52 lockinit(struct lock *lkp, int prio, char *wmesg, int timo, int flags) 53 { 54 KASSERT(flags == 0); 55 56 memset(lkp, 0, sizeof(struct lock)); 57 rrw_init(&lkp->lk_lck, wmesg); 58 } 59 60 int 61 lockstatus(struct lock *lkp) 62 { 63 switch (rrw_status(&lkp->lk_lck)) { 64 case RW_WRITE: 65 return (LK_EXCLUSIVE); 66 case RW_WRITE_OTHER: 67 return (LK_EXCLOTHER); 68 case RW_READ: 69 return (LK_SHARED); 70 case 0: 71 default: 72 return (0); 73 } 74 } 75 76 int 77 lockmgr(struct lock *lkp, u_int flags, void *notused) 78 { 79 int rwflags = 0; 80 81 KASSERT(!((flags & (LK_SHARED|LK_EXCLUSIVE)) == 82 (LK_SHARED|LK_EXCLUSIVE))); 83 KASSERT(!((flags & (LK_CANRECURSE|LK_RECURSEFAIL)) == 84 (LK_CANRECURSE|LK_RECURSEFAIL))); 85 KASSERT((flags & LK_RELEASE) || 86 (flags & (LK_SHARED|LK_EXCLUSIVE|LK_DRAIN))); 87 88 if (flags & LK_RELEASE) { 89 rrw_exit(&lkp->lk_lck); 90 return (0); 91 } 92 if (flags & LK_SHARED) 93 rwflags |= RW_READ; 94 if (flags & (LK_EXCLUSIVE|LK_DRAIN)) 95 rwflags |= RW_WRITE; 96 if (flags & LK_RECURSEFAIL) 97 rwflags |= RW_RECURSEFAIL; 98 if (flags & LK_NOWAIT) 99 rwflags |= RW_NOSLEEP; 100 101 return (rrw_enter(&lkp->lk_lck, rwflags)); 102 103 } 104 105 #if defined(MULTIPROCESSOR) 106 /* 107 * Functions for manipulating the kernel_lock. We put them here 108 * so that they show up in profiles. 109 */ 110 111 struct __mp_lock kernel_lock; 112 113 void 114 _kernel_lock_init(void) 115 { 116 __mp_lock_init(&kernel_lock); 117 } 118 119 /* 120 * Acquire/release the kernel lock. Intended for use in the scheduler 121 * and the lower half of the kernel. 122 */ 123 124 void 125 _kernel_lock(void) 126 { 127 SCHED_ASSERT_UNLOCKED(); 128 __mp_lock(&kernel_lock); 129 } 130 131 void 132 _kernel_unlock(void) 133 { 134 __mp_unlock(&kernel_lock); 135 } 136 137 int 138 _kernel_lock_held(void) 139 { 140 return (__mp_lock_held(&kernel_lock)); 141 } 142 #endif /* MULTIPROCESSOR */ 143