1 /* $NetBSD: kern_lock.c,v 1.147 2008/11/12 12:36:16 ad Exp $ */ 2 3 /*- 4 * Copyright (c) 2002, 2006, 2007, 2008 The NetBSD Foundation, Inc. 5 * All rights reserved. 6 * 7 * This code is derived from software contributed to The NetBSD Foundation 8 * by Jason R. Thorpe of the Numerical Aerospace Simulation Facility, 9 * NASA Ames Research Center, and by Andrew Doran. 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 * 20 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS 21 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 22 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 23 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS 24 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 25 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 26 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 27 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 28 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 29 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 30 * POSSIBILITY OF SUCH DAMAGE. 31 */ 32 33 #include <sys/cdefs.h> 34 __KERNEL_RCSID(0, "$NetBSD: kern_lock.c,v 1.147 2008/11/12 12:36:16 ad Exp $"); 35 36 #include <sys/param.h> 37 #include <sys/proc.h> 38 #include <sys/lock.h> 39 #include <sys/systm.h> 40 #include <sys/kernel.h> 41 #include <sys/lockdebug.h> 42 #include <sys/cpu.h> 43 #include <sys/syslog.h> 44 #include <sys/atomic.h> 45 46 #include <machine/stdarg.h> 47 #include <machine/lock.h> 48 49 #include <dev/lockstat.h> 50 51 #define RETURN_ADDRESS (uintptr_t)__builtin_return_address(0) 52 53 bool kernel_lock_dodebug; 54 55 __cpu_simple_lock_t kernel_lock[CACHE_LINE_SIZE / sizeof(__cpu_simple_lock_t)] 56 __aligned(CACHE_LINE_SIZE); 57 58 void 59 assert_sleepable(void) 60 { 61 const char *reason; 62 63 if (panicstr != NULL) { 64 return; 65 } 66 67 LOCKDEBUG_BARRIER(kernel_lock, 1); 68 69 reason = NULL; 70 if (CURCPU_IDLE_P() && !cold) { 71 reason = "idle"; 72 } 73 if (cpu_intr_p()) { 74 reason = "interrupt"; 75 } 76 if ((curlwp->l_pflag & LP_INTR) != 0) { 77 reason = "softint"; 78 } 79 80 if (reason) { 81 panic("%s: %s caller=%p", __func__, reason, 82 (void *)RETURN_ADDRESS); 83 } 84 } 85 86 /* 87 * Functions for manipulating the kernel_lock. We put them here 88 * so that they show up in profiles. 89 */ 90 91 #define _KERNEL_LOCK_ABORT(msg) \ 92 LOCKDEBUG_ABORT(kernel_lock, &_kernel_lock_ops, __func__, msg) 93 94 #ifdef LOCKDEBUG 95 #define _KERNEL_LOCK_ASSERT(cond) \ 96 do { \ 97 if (!(cond)) \ 98 _KERNEL_LOCK_ABORT("assertion failed: " #cond); \ 99 } while (/* CONSTCOND */ 0) 100 #else 101 #define _KERNEL_LOCK_ASSERT(cond) /* nothing */ 102 #endif 103 104 void _kernel_lock_dump(volatile void *); 105 106 lockops_t _kernel_lock_ops = { 107 "Kernel lock", 108 LOCKOPS_SPIN, 109 _kernel_lock_dump 110 }; 111 112 /* 113 * Initialize the kernel lock. 114 */ 115 void 116 kernel_lock_init(void) 117 { 118 119 CTASSERT(CACHE_LINE_SIZE >= sizeof(__cpu_simple_lock_t)); 120 __cpu_simple_lock_init(kernel_lock); 121 kernel_lock_dodebug = LOCKDEBUG_ALLOC(kernel_lock, &_kernel_lock_ops, 122 RETURN_ADDRESS); 123 } 124 125 /* 126 * Print debugging information about the kernel lock. 127 */ 128 void 129 _kernel_lock_dump(volatile void *junk) 130 { 131 struct cpu_info *ci = curcpu(); 132 133 (void)junk; 134 135 printf_nolog("curcpu holds : %18d wanted by: %#018lx\n", 136 ci->ci_biglock_count, (long)ci->ci_biglock_wanted); 137 } 138 139 /* 140 * Acquire 'nlocks' holds on the kernel lock. If 'l' is non-null, the 141 * acquisition is from process context. 142 */ 143 void 144 _kernel_lock(int nlocks) 145 { 146 struct cpu_info *ci; 147 LOCKSTAT_TIMER(spintime); 148 LOCKSTAT_FLAG(lsflag); 149 struct lwp *owant; 150 u_int spins; 151 int s; 152 struct lwp *l = curlwp; 153 154 _KERNEL_LOCK_ASSERT(nlocks > 0); 155 156 s = splvm(); 157 ci = curcpu(); 158 if (ci->ci_biglock_count != 0) { 159 _KERNEL_LOCK_ASSERT(__SIMPLELOCK_LOCKED_P(kernel_lock)); 160 ci->ci_biglock_count += nlocks; 161 l->l_blcnt += nlocks; 162 splx(s); 163 return; 164 } 165 166 _KERNEL_LOCK_ASSERT(l->l_blcnt == 0); 167 LOCKDEBUG_WANTLOCK(kernel_lock_dodebug, kernel_lock, RETURN_ADDRESS, 168 false, false); 169 170 if (__cpu_simple_lock_try(kernel_lock)) { 171 ci->ci_biglock_count = nlocks; 172 l->l_blcnt = nlocks; 173 LOCKDEBUG_LOCKED(kernel_lock_dodebug, kernel_lock, NULL, 174 RETURN_ADDRESS, 0); 175 splx(s); 176 return; 177 } 178 179 /* 180 * To remove the ordering constraint between adaptive mutexes 181 * and kernel_lock we must make it appear as if this thread is 182 * blocking. For non-interlocked mutex release, a store fence 183 * is required to ensure that the result of any mutex_exit() 184 * by the current LWP becomes visible on the bus before the set 185 * of ci->ci_biglock_wanted becomes visible. 186 */ 187 membar_producer(); 188 owant = ci->ci_biglock_wanted; 189 ci->ci_biglock_wanted = l; 190 191 /* 192 * Spin until we acquire the lock. Once we have it, record the 193 * time spent with lockstat. 194 */ 195 LOCKSTAT_ENTER(lsflag); 196 LOCKSTAT_START_TIMER(lsflag, spintime); 197 198 spins = 0; 199 do { 200 splx(s); 201 while (__SIMPLELOCK_LOCKED_P(kernel_lock)) { 202 if (SPINLOCK_SPINOUT(spins)) { 203 extern int start_init_exec; 204 if (!start_init_exec) 205 _KERNEL_LOCK_ABORT("spinout"); 206 } 207 SPINLOCK_BACKOFF_HOOK; 208 SPINLOCK_SPIN_HOOK; 209 } 210 s = splvm(); 211 } while (!__cpu_simple_lock_try(kernel_lock)); 212 213 ci->ci_biglock_count = nlocks; 214 l->l_blcnt = nlocks; 215 LOCKSTAT_STOP_TIMER(lsflag, spintime); 216 LOCKDEBUG_LOCKED(kernel_lock_dodebug, kernel_lock, NULL, 217 RETURN_ADDRESS, 0); 218 if (owant == NULL) { 219 LOCKSTAT_EVENT_RA(lsflag, kernel_lock, 220 LB_KERNEL_LOCK | LB_SPIN, 1, spintime, RETURN_ADDRESS); 221 } 222 LOCKSTAT_EXIT(lsflag); 223 splx(s); 224 225 /* 226 * Now that we have kernel_lock, reset ci_biglock_wanted. This 227 * store must be unbuffered (immediately visible on the bus) in 228 * order for non-interlocked mutex release to work correctly. 229 * It must be visible before a mutex_exit() can execute on this 230 * processor. 231 * 232 * Note: only where CAS is available in hardware will this be 233 * an unbuffered write, but non-interlocked release cannot be 234 * done on CPUs without CAS in hardware. 235 */ 236 (void)atomic_swap_ptr(&ci->ci_biglock_wanted, owant); 237 238 /* 239 * Issue a memory barrier as we have acquired a lock. This also 240 * prevents stores from a following mutex_exit() being reordered 241 * to occur before our store to ci_biglock_wanted above. 242 */ 243 membar_enter(); 244 } 245 246 /* 247 * Release 'nlocks' holds on the kernel lock. If 'nlocks' is zero, release 248 * all holds. If 'l' is non-null, the release is from process context. 249 */ 250 void 251 _kernel_unlock(int nlocks, int *countp) 252 { 253 struct cpu_info *ci; 254 u_int olocks; 255 int s; 256 struct lwp *l = curlwp; 257 258 _KERNEL_LOCK_ASSERT(nlocks < 2); 259 260 olocks = l->l_blcnt; 261 262 if (olocks == 0) { 263 _KERNEL_LOCK_ASSERT(nlocks <= 0); 264 if (countp != NULL) 265 *countp = 0; 266 return; 267 } 268 269 _KERNEL_LOCK_ASSERT(__SIMPLELOCK_LOCKED_P(kernel_lock)); 270 271 if (nlocks == 0) 272 nlocks = olocks; 273 else if (nlocks == -1) { 274 nlocks = 1; 275 _KERNEL_LOCK_ASSERT(olocks == 1); 276 } 277 s = splvm(); 278 ci = curcpu(); 279 _KERNEL_LOCK_ASSERT(ci->ci_biglock_count >= l->l_blcnt); 280 if (ci->ci_biglock_count == nlocks) { 281 LOCKDEBUG_UNLOCKED(kernel_lock_dodebug, kernel_lock, 282 RETURN_ADDRESS, 0); 283 ci->ci_biglock_count = 0; 284 __cpu_simple_unlock(kernel_lock); 285 l->l_blcnt -= nlocks; 286 splx(s); 287 if (l->l_dopreempt) 288 kpreempt(0); 289 } else { 290 ci->ci_biglock_count -= nlocks; 291 l->l_blcnt -= nlocks; 292 splx(s); 293 } 294 295 if (countp != NULL) 296 *countp = olocks; 297 } 298