| 1 | /* $NetBSD: kern_lock.c,v 1.157 2015/04/11 15:24:25 skrll Exp $ */ |
| 2 | |
| 3 | /*- |
| 4 | * Copyright (c) 2002, 2006, 2007, 2008, 2009 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 1.157 2015/04/11 15:24:25 skrll 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 | #include <sys/lwp.h> |
| 46 | |
| 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 | __cacheline_aligned; |
| 57 | |
| 58 | void |
| 59 | assert_sleepable(void) |
| 60 | { |
| 61 | const char *reason; |
| 62 | uint64_t pctr; |
| 63 | bool idle; |
| 64 | |
| 65 | if (panicstr != NULL) { |
| 66 | return; |
| 67 | } |
| 68 | |
| 69 | LOCKDEBUG_BARRIER(kernel_lock, 1); |
| 70 | |
| 71 | /* |
| 72 | * Avoid disabling/re-enabling preemption here since this |
| 73 | * routine may be called in delicate situations. |
| 74 | */ |
| 75 | do { |
| 76 | pctr = lwp_pctr(); |
| 77 | idle = CURCPU_IDLE_P(); |
| 78 | } while (pctr != lwp_pctr()); |
| 79 | |
| 80 | reason = NULL; |
| 81 | if (idle && !cold && |
| 82 | kcpuset_isset(kcpuset_running, cpu_index(curcpu()))) { |
| 83 | reason = "idle" ; |
| 84 | } |
| 85 | if (cpu_intr_p()) { |
| 86 | reason = "interrupt" ; |
| 87 | } |
| 88 | if (cpu_softintr_p()) { |
| 89 | reason = "softint" ; |
| 90 | } |
| 91 | |
| 92 | if (reason) { |
| 93 | panic("%s: %s caller=%p" , __func__, reason, |
| 94 | (void *)RETURN_ADDRESS); |
| 95 | } |
| 96 | } |
| 97 | |
| 98 | /* |
| 99 | * Functions for manipulating the kernel_lock. We put them here |
| 100 | * so that they show up in profiles. |
| 101 | */ |
| 102 | |
| 103 | #define _KERNEL_LOCK_ABORT(msg) \ |
| 104 | LOCKDEBUG_ABORT(kernel_lock, &_kernel_lock_ops, __func__, msg) |
| 105 | |
| 106 | #ifdef LOCKDEBUG |
| 107 | #define _KERNEL_LOCK_ASSERT(cond) \ |
| 108 | do { \ |
| 109 | if (!(cond)) \ |
| 110 | _KERNEL_LOCK_ABORT("assertion failed: " #cond); \ |
| 111 | } while (/* CONSTCOND */ 0) |
| 112 | #else |
| 113 | #define _KERNEL_LOCK_ASSERT(cond) /* nothing */ |
| 114 | #endif |
| 115 | |
| 116 | void _kernel_lock_dump(volatile void *); |
| 117 | |
| 118 | lockops_t _kernel_lock_ops = { |
| 119 | "Kernel lock" , |
| 120 | LOCKOPS_SPIN, |
| 121 | _kernel_lock_dump |
| 122 | }; |
| 123 | |
| 124 | /* |
| 125 | * Initialize the kernel lock. |
| 126 | */ |
| 127 | void |
| 128 | kernel_lock_init(void) |
| 129 | { |
| 130 | |
| 131 | __cpu_simple_lock_init(kernel_lock); |
| 132 | kernel_lock_dodebug = LOCKDEBUG_ALLOC(kernel_lock, &_kernel_lock_ops, |
| 133 | RETURN_ADDRESS); |
| 134 | } |
| 135 | CTASSERT(CACHE_LINE_SIZE >= sizeof(__cpu_simple_lock_t)); |
| 136 | |
| 137 | /* |
| 138 | * Print debugging information about the kernel lock. |
| 139 | */ |
| 140 | void |
| 141 | _kernel_lock_dump(volatile void *junk) |
| 142 | { |
| 143 | struct cpu_info *ci = curcpu(); |
| 144 | |
| 145 | (void)junk; |
| 146 | |
| 147 | printf_nolog("curcpu holds : %18d wanted by: %#018lx\n" , |
| 148 | ci->ci_biglock_count, (long)ci->ci_biglock_wanted); |
| 149 | } |
| 150 | |
| 151 | /* |
| 152 | * Acquire 'nlocks' holds on the kernel lock. |
| 153 | */ |
| 154 | void |
| 155 | _kernel_lock(int nlocks) |
| 156 | { |
| 157 | struct cpu_info *ci; |
| 158 | LOCKSTAT_TIMER(spintime); |
| 159 | LOCKSTAT_FLAG(lsflag); |
| 160 | struct lwp *owant; |
| 161 | u_int spins; |
| 162 | int s; |
| 163 | struct lwp *l = curlwp; |
| 164 | |
| 165 | _KERNEL_LOCK_ASSERT(nlocks > 0); |
| 166 | |
| 167 | s = splvm(); |
| 168 | ci = curcpu(); |
| 169 | if (ci->ci_biglock_count != 0) { |
| 170 | _KERNEL_LOCK_ASSERT(__SIMPLELOCK_LOCKED_P(kernel_lock)); |
| 171 | ci->ci_biglock_count += nlocks; |
| 172 | l->l_blcnt += nlocks; |
| 173 | splx(s); |
| 174 | return; |
| 175 | } |
| 176 | |
| 177 | _KERNEL_LOCK_ASSERT(l->l_blcnt == 0); |
| 178 | LOCKDEBUG_WANTLOCK(kernel_lock_dodebug, kernel_lock, RETURN_ADDRESS, |
| 179 | 0); |
| 180 | |
| 181 | if (__cpu_simple_lock_try(kernel_lock)) { |
| 182 | ci->ci_biglock_count = nlocks; |
| 183 | l->l_blcnt = nlocks; |
| 184 | LOCKDEBUG_LOCKED(kernel_lock_dodebug, kernel_lock, NULL, |
| 185 | RETURN_ADDRESS, 0); |
| 186 | splx(s); |
| 187 | return; |
| 188 | } |
| 189 | |
| 190 | /* |
| 191 | * To remove the ordering constraint between adaptive mutexes |
| 192 | * and kernel_lock we must make it appear as if this thread is |
| 193 | * blocking. For non-interlocked mutex release, a store fence |
| 194 | * is required to ensure that the result of any mutex_exit() |
| 195 | * by the current LWP becomes visible on the bus before the set |
| 196 | * of ci->ci_biglock_wanted becomes visible. |
| 197 | */ |
| 198 | membar_producer(); |
| 199 | owant = ci->ci_biglock_wanted; |
| 200 | ci->ci_biglock_wanted = l; |
| 201 | |
| 202 | /* |
| 203 | * Spin until we acquire the lock. Once we have it, record the |
| 204 | * time spent with lockstat. |
| 205 | */ |
| 206 | LOCKSTAT_ENTER(lsflag); |
| 207 | LOCKSTAT_START_TIMER(lsflag, spintime); |
| 208 | |
| 209 | spins = 0; |
| 210 | do { |
| 211 | splx(s); |
| 212 | while (__SIMPLELOCK_LOCKED_P(kernel_lock)) { |
| 213 | if (SPINLOCK_SPINOUT(spins)) { |
| 214 | extern int start_init_exec; |
| 215 | if (!start_init_exec) |
| 216 | _KERNEL_LOCK_ABORT("spinout" ); |
| 217 | } |
| 218 | SPINLOCK_BACKOFF_HOOK; |
| 219 | SPINLOCK_SPIN_HOOK; |
| 220 | } |
| 221 | s = splvm(); |
| 222 | } while (!__cpu_simple_lock_try(kernel_lock)); |
| 223 | |
| 224 | ci->ci_biglock_count = nlocks; |
| 225 | l->l_blcnt = nlocks; |
| 226 | LOCKSTAT_STOP_TIMER(lsflag, spintime); |
| 227 | LOCKDEBUG_LOCKED(kernel_lock_dodebug, kernel_lock, NULL, |
| 228 | RETURN_ADDRESS, 0); |
| 229 | if (owant == NULL) { |
| 230 | LOCKSTAT_EVENT_RA(lsflag, kernel_lock, |
| 231 | LB_KERNEL_LOCK | LB_SPIN, 1, spintime, RETURN_ADDRESS); |
| 232 | } |
| 233 | LOCKSTAT_EXIT(lsflag); |
| 234 | splx(s); |
| 235 | |
| 236 | /* |
| 237 | * Now that we have kernel_lock, reset ci_biglock_wanted. This |
| 238 | * store must be unbuffered (immediately visible on the bus) in |
| 239 | * order for non-interlocked mutex release to work correctly. |
| 240 | * It must be visible before a mutex_exit() can execute on this |
| 241 | * processor. |
| 242 | * |
| 243 | * Note: only where CAS is available in hardware will this be |
| 244 | * an unbuffered write, but non-interlocked release cannot be |
| 245 | * done on CPUs without CAS in hardware. |
| 246 | */ |
| 247 | (void)atomic_swap_ptr(&ci->ci_biglock_wanted, owant); |
| 248 | |
| 249 | /* |
| 250 | * Issue a memory barrier as we have acquired a lock. This also |
| 251 | * prevents stores from a following mutex_exit() being reordered |
| 252 | * to occur before our store to ci_biglock_wanted above. |
| 253 | */ |
| 254 | membar_enter(); |
| 255 | } |
| 256 | |
| 257 | /* |
| 258 | * Release 'nlocks' holds on the kernel lock. If 'nlocks' is zero, release |
| 259 | * all holds. |
| 260 | */ |
| 261 | void |
| 262 | _kernel_unlock(int nlocks, int *countp) |
| 263 | { |
| 264 | struct cpu_info *ci; |
| 265 | u_int olocks; |
| 266 | int s; |
| 267 | struct lwp *l = curlwp; |
| 268 | |
| 269 | _KERNEL_LOCK_ASSERT(nlocks < 2); |
| 270 | |
| 271 | olocks = l->l_blcnt; |
| 272 | |
| 273 | if (olocks == 0) { |
| 274 | _KERNEL_LOCK_ASSERT(nlocks <= 0); |
| 275 | if (countp != NULL) |
| 276 | *countp = 0; |
| 277 | return; |
| 278 | } |
| 279 | |
| 280 | _KERNEL_LOCK_ASSERT(__SIMPLELOCK_LOCKED_P(kernel_lock)); |
| 281 | |
| 282 | if (nlocks == 0) |
| 283 | nlocks = olocks; |
| 284 | else if (nlocks == -1) { |
| 285 | nlocks = 1; |
| 286 | _KERNEL_LOCK_ASSERT(olocks == 1); |
| 287 | } |
| 288 | s = splvm(); |
| 289 | ci = curcpu(); |
| 290 | _KERNEL_LOCK_ASSERT(ci->ci_biglock_count >= l->l_blcnt); |
| 291 | if (ci->ci_biglock_count == nlocks) { |
| 292 | LOCKDEBUG_UNLOCKED(kernel_lock_dodebug, kernel_lock, |
| 293 | RETURN_ADDRESS, 0); |
| 294 | ci->ci_biglock_count = 0; |
| 295 | __cpu_simple_unlock(kernel_lock); |
| 296 | l->l_blcnt -= nlocks; |
| 297 | splx(s); |
| 298 | if (l->l_dopreempt) |
| 299 | kpreempt(0); |
| 300 | } else { |
| 301 | ci->ci_biglock_count -= nlocks; |
| 302 | l->l_blcnt -= nlocks; |
| 303 | splx(s); |
| 304 | } |
| 305 | |
| 306 | if (countp != NULL) |
| 307 | *countp = olocks; |
| 308 | } |
| 309 | |
| 310 | bool |
| 311 | _kernel_locked_p(void) |
| 312 | { |
| 313 | return __SIMPLELOCK_LOCKED_P(kernel_lock); |
| 314 | } |
| 315 | |