1 /* $OpenBSD: kern_lock.c,v 1.45 2014/07/13 15:46:21 uebayasi 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/proc.h> 40 #include <sys/lock.h> 41 #include <sys/systm.h> 42 #include <sys/sched.h> 43 44 #ifdef MP_LOCKDEBUG 45 /* CPU-dependent timing, this needs to be settable from ddb. */ 46 int __mp_lock_spinout = 200000000; 47 #endif 48 49 /* 50 * Initialize a lock; required before use. 51 */ 52 void 53 lockinit(struct lock *lkp, int prio, char *wmesg, int timo, int flags) 54 { 55 KASSERT(flags == 0); 56 57 memset(lkp, 0, sizeof(struct lock)); 58 rrw_init(&lkp->lk_lck, wmesg); 59 } 60 61 int 62 lockstatus(struct lock *lkp) 63 { 64 switch (rrw_status(&lkp->lk_lck)) { 65 case RW_WRITE: 66 return (LK_EXCLUSIVE); 67 case RW_WRITE_OTHER: 68 return (LK_EXCLOTHER); 69 case RW_READ: 70 return (LK_SHARED); 71 case 0: 72 default: 73 return (0); 74 } 75 } 76 77 int 78 lockmgr(struct lock *lkp, u_int flags, void *notused) 79 { 80 int rwflags = 0; 81 82 KASSERT(!((flags & (LK_SHARED|LK_EXCLUSIVE)) == 83 (LK_SHARED|LK_EXCLUSIVE))); 84 KASSERT(!((flags & (LK_CANRECURSE|LK_RECURSEFAIL)) == 85 (LK_CANRECURSE|LK_RECURSEFAIL))); 86 KASSERT((flags & LK_RELEASE) || 87 (flags & (LK_SHARED|LK_EXCLUSIVE|LK_DRAIN))); 88 89 if (flags & LK_RELEASE) { 90 rrw_exit(&lkp->lk_lck); 91 return (0); 92 } 93 if (flags & LK_SHARED) 94 rwflags |= RW_READ; 95 if (flags & (LK_EXCLUSIVE|LK_DRAIN)) 96 rwflags |= RW_WRITE; 97 if (flags & LK_RECURSEFAIL) 98 rwflags |= RW_RECURSEFAIL; 99 if (flags & LK_NOWAIT) 100 rwflags |= RW_NOSLEEP; 101 102 return (rrw_enter(&lkp->lk_lck, rwflags)); 103 104 } 105 106 #if defined(MULTIPROCESSOR) 107 /* 108 * Functions for manipulating the kernel_lock. We put them here 109 * so that they show up in profiles. 110 */ 111 112 struct __mp_lock kernel_lock; 113 114 void 115 _kernel_lock_init(void) 116 { 117 __mp_lock_init(&kernel_lock); 118 } 119 120 /* 121 * Acquire/release the kernel lock. Intended for use in the scheduler 122 * and the lower half of the kernel. 123 */ 124 125 void 126 _kernel_lock(void) 127 { 128 SCHED_ASSERT_UNLOCKED(); 129 __mp_lock(&kernel_lock); 130 } 131 132 void 133 _kernel_unlock(void) 134 { 135 __mp_unlock(&kernel_lock); 136 } 137 138 int 139 _kernel_lock_held(void) 140 { 141 return (__mp_lock_held(&kernel_lock)); 142 } 143 #endif /* MULTIPROCESSOR */ 144