1 /* 2 * Copyright (c) 1995 3 * The Regents of the University of California. All rights reserved. 4 * 5 * Copyright (C) 1997 6 * John S. Dyson. All rights reserved. 7 * 8 * This code contains ideas from software contributed to Berkeley by 9 * Avadis Tevanian, Jr., Michael Wayne Young, and the Mach Operating 10 * System project at Carnegie-Mellon University. 11 * 12 * Redistribution and use in source and binary forms, with or without 13 * modification, are permitted provided that the following conditions 14 * are met: 15 * 1. Redistributions of source code must retain the above copyright 16 * notice, this list of conditions and the following disclaimer. 17 * 2. Redistributions in binary form must reproduce the above copyright 18 * notice, this list of conditions and the following disclaimer in the 19 * documentation and/or other materials provided with the distribution. 20 * 3. All advertising materials mentioning features or use of this software 21 * must display the following acknowledgement: 22 * This product includes software developed by the University of 23 * California, Berkeley and its contributors. 24 * 4. Neither the name of the University nor the names of its contributors 25 * may be used to endorse or promote products derived from this software 26 * without specific prior written permission. 27 * 28 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 29 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 30 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 31 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 32 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 33 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 34 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 35 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 36 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 37 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 38 * SUCH DAMAGE. 39 * 40 * @(#)kern_lock.c 8.18 (Berkeley) 5/21/95 41 * $FreeBSD: src/sys/kern/kern_lock.c,v 1.31.2.3 2001/12/25 01:44:44 dillon Exp $ 42 * $DragonFly: src/sys/kern/kern_lock.c,v 1.6 2003/08/25 19:50:32 dillon Exp $ 43 */ 44 45 #include "opt_lint.h" 46 47 #include <sys/param.h> 48 #include <sys/proc.h> 49 #include <sys/lock.h> 50 #include <sys/systm.h> 51 52 /* 53 * Locking primitives implementation. 54 * Locks provide shared/exclusive sychronization. 55 */ 56 57 #ifdef SIMPLELOCK_DEBUG 58 #define COUNT(td, x) (td)->td_locks += (x) 59 #else 60 #define COUNT(td, x) 61 #endif 62 63 #define LOCK_WAIT_TIME 100 64 #define LOCK_SAMPLE_WAIT 7 65 66 #if defined(DIAGNOSTIC) 67 #define LOCK_INLINE 68 #else 69 #define LOCK_INLINE __inline 70 #endif 71 72 #define LK_ALL (LK_HAVE_EXCL | LK_WANT_EXCL | LK_WANT_UPGRADE | \ 73 LK_SHARE_NONZERO | LK_WAIT_NONZERO) 74 75 static int acquire(struct lock *lkp, int extflags, int wanted); 76 static int acquiredrain(struct lock *lkp, int extflags) ; 77 78 static LOCK_INLINE void 79 sharelock(struct lock *lkp, int incr) { 80 lkp->lk_flags |= LK_SHARE_NONZERO; 81 lkp->lk_sharecount += incr; 82 } 83 84 static LOCK_INLINE void 85 shareunlock(struct lock *lkp, int decr) { 86 87 KASSERT(lkp->lk_sharecount >= decr, ("shareunlock: count < decr")); 88 89 if (lkp->lk_sharecount == decr) { 90 lkp->lk_flags &= ~LK_SHARE_NONZERO; 91 if (lkp->lk_flags & (LK_WANT_UPGRADE | LK_WANT_EXCL)) { 92 wakeup(lkp); 93 } 94 lkp->lk_sharecount = 0; 95 } else { 96 lkp->lk_sharecount -= decr; 97 } 98 } 99 100 static int 101 acquire(struct lock *lkp, int extflags, int wanted) 102 { 103 int s, error; 104 105 if ((extflags & LK_NOWAIT) && (lkp->lk_flags & wanted)) { 106 return EBUSY; 107 } 108 109 if (((lkp->lk_flags | extflags) & LK_NOPAUSE) == 0) { 110 if ((lkp->lk_flags & wanted) == 0) 111 return 0; 112 } 113 114 s = splhigh(); 115 while ((lkp->lk_flags & wanted) != 0) { 116 lkp->lk_flags |= LK_WAIT_NONZERO; 117 lkp->lk_waitcount++; 118 lwkt_reltoken(&lkp->lk_interlock); 119 error = tsleep(lkp, lkp->lk_prio, lkp->lk_wmesg, 120 ((extflags & LK_TIMELOCK) ? lkp->lk_timo : 0)); 121 lwkt_gettoken(&lkp->lk_interlock); 122 if (lkp->lk_waitcount == 1) { 123 lkp->lk_flags &= ~LK_WAIT_NONZERO; 124 lkp->lk_waitcount = 0; 125 } else { 126 lkp->lk_waitcount--; 127 } 128 if (error) { 129 splx(s); 130 return error; 131 } 132 if (extflags & LK_SLEEPFAIL) { 133 splx(s); 134 return ENOLCK; 135 } 136 } 137 splx(s); 138 return 0; 139 } 140 141 /* 142 * Set, change, or release a lock. 143 * 144 * Shared requests increment the shared count. Exclusive requests set the 145 * LK_WANT_EXCL flag (preventing further shared locks), and wait for already 146 * accepted shared locks and shared-to-exclusive upgrades to go away. 147 */ 148 int 149 #ifndef DEBUG_LOCKS 150 lockmgr(struct lock *lkp, u_int flags, struct lwkt_token *interlkp, 151 struct thread *td) 152 #else 153 debuglockmgr(struct lock *lkp, u_int flags, struct lwkt_token *interlkp, 154 struct thread *td, const char *name, const char *file, int line) 155 #endif 156 { 157 int error; 158 int extflags; 159 160 error = 0; 161 162 /*if ((flags & LK_NOWAIT) == 0 && (flags & LK_TYPE_MASK) != LK_RELEASE)*/ { 163 #ifndef DEBUG_LOCKS 164 if (mycpu->gd_intr_nesting_level) 165 printf("lockmgr %s from %p: called from FASTint\n", lkp->lk_wmesg, ((int **)&lkp)[-1]); 166 #else 167 if (mycpu->gd_intr_nesting_level) 168 printf("lockmgr %s from %s:%d: called from FASTint\n", lkp->lk_wmesg, file, line); 169 #endif 170 } 171 172 lwkt_gettoken(&lkp->lk_interlock); 173 if (flags & LK_INTERLOCK) 174 lwkt_reltoken(interlkp); 175 176 extflags = (flags | lkp->lk_flags) & LK_EXTFLG_MASK; 177 178 switch (flags & LK_TYPE_MASK) { 179 180 case LK_SHARED: 181 /* 182 * If we are not the exclusive lock holder, we have to block 183 * while there is an exclusive lock holder or while an 184 * exclusive lock request or upgrade request is in progress. 185 * 186 * However, if P_DEADLKTREAT is set, we override exclusive 187 * lock requests or upgrade requests ( but not the exclusive 188 * lock itself ). 189 */ 190 if (lkp->lk_lockholder != td) { 191 if (td->td_flags & TDF_DEADLKTREAT) { 192 error = acquire( 193 lkp, 194 extflags, 195 LK_HAVE_EXCL 196 ); 197 } else { 198 error = acquire( 199 lkp, 200 extflags, 201 LK_HAVE_EXCL | LK_WANT_EXCL | 202 LK_WANT_UPGRADE 203 ); 204 } 205 if (error) 206 break; 207 sharelock(lkp, 1); 208 COUNT(td, 1); 209 break; 210 } 211 /* 212 * We hold an exclusive lock, so downgrade it to shared. 213 * An alternative would be to fail with EDEADLK. 214 */ 215 sharelock(lkp, 1); 216 COUNT(td, 1); 217 /* fall into downgrade */ 218 219 case LK_DOWNGRADE: 220 if (lkp->lk_lockholder != td || lkp->lk_exclusivecount == 0) 221 panic("lockmgr: not holding exclusive lock"); 222 sharelock(lkp, lkp->lk_exclusivecount); 223 lkp->lk_exclusivecount = 0; 224 lkp->lk_flags &= ~LK_HAVE_EXCL; 225 lkp->lk_lockholder = LK_NOTHREAD; 226 if (lkp->lk_waitcount) 227 wakeup((void *)lkp); 228 break; 229 230 case LK_EXCLUPGRADE: 231 /* 232 * If another process is ahead of us to get an upgrade, 233 * then we want to fail rather than have an intervening 234 * exclusive access. 235 */ 236 if (lkp->lk_flags & LK_WANT_UPGRADE) { 237 shareunlock(lkp, 1); 238 COUNT(td, -1); 239 error = EBUSY; 240 break; 241 } 242 /* fall into normal upgrade */ 243 244 case LK_UPGRADE: 245 /* 246 * Upgrade a shared lock to an exclusive one. If another 247 * shared lock has already requested an upgrade to an 248 * exclusive lock, our shared lock is released and an 249 * exclusive lock is requested (which will be granted 250 * after the upgrade). If we return an error, the file 251 * will always be unlocked. 252 */ 253 if ((lkp->lk_lockholder == td) || (lkp->lk_sharecount <= 0)) 254 panic("lockmgr: upgrade exclusive lock"); 255 shareunlock(lkp, 1); 256 COUNT(td, -1); 257 /* 258 * If we are just polling, check to see if we will block. 259 */ 260 if ((extflags & LK_NOWAIT) && 261 ((lkp->lk_flags & LK_WANT_UPGRADE) || 262 lkp->lk_sharecount > 1)) { 263 error = EBUSY; 264 break; 265 } 266 if ((lkp->lk_flags & LK_WANT_UPGRADE) == 0) { 267 /* 268 * We are first shared lock to request an upgrade, so 269 * request upgrade and wait for the shared count to 270 * drop to zero, then take exclusive lock. 271 */ 272 lkp->lk_flags |= LK_WANT_UPGRADE; 273 error = acquire(lkp, extflags, LK_SHARE_NONZERO); 274 lkp->lk_flags &= ~LK_WANT_UPGRADE; 275 276 if (error) 277 break; 278 lkp->lk_flags |= LK_HAVE_EXCL; 279 lkp->lk_lockholder = td; 280 if (lkp->lk_exclusivecount != 0) 281 panic("lockmgr: non-zero exclusive count"); 282 lkp->lk_exclusivecount = 1; 283 #if defined(DEBUG_LOCKS) 284 lkp->lk_filename = file; 285 lkp->lk_lineno = line; 286 lkp->lk_lockername = name; 287 #endif 288 COUNT(td, 1); 289 break; 290 } 291 /* 292 * Someone else has requested upgrade. Release our shared 293 * lock, awaken upgrade requestor if we are the last shared 294 * lock, then request an exclusive lock. 295 */ 296 if ( (lkp->lk_flags & (LK_SHARE_NONZERO|LK_WAIT_NONZERO)) == 297 LK_WAIT_NONZERO) 298 wakeup((void *)lkp); 299 /* fall into exclusive request */ 300 301 case LK_EXCLUSIVE: 302 if (lkp->lk_lockholder == td && td != LK_KERNTHREAD) { 303 /* 304 * Recursive lock. 305 */ 306 if ((extflags & (LK_NOWAIT | LK_CANRECURSE)) == 0) 307 panic("lockmgr: locking against myself"); 308 if ((extflags & LK_CANRECURSE) != 0) { 309 lkp->lk_exclusivecount++; 310 COUNT(td, 1); 311 break; 312 } 313 } 314 /* 315 * If we are just polling, check to see if we will sleep. 316 */ 317 if ((extflags & LK_NOWAIT) && 318 (lkp->lk_flags & (LK_HAVE_EXCL | LK_WANT_EXCL | LK_WANT_UPGRADE | LK_SHARE_NONZERO))) { 319 error = EBUSY; 320 break; 321 } 322 /* 323 * Try to acquire the want_exclusive flag. 324 */ 325 error = acquire(lkp, extflags, (LK_HAVE_EXCL | LK_WANT_EXCL)); 326 if (error) 327 break; 328 lkp->lk_flags |= LK_WANT_EXCL; 329 /* 330 * Wait for shared locks and upgrades to finish. 331 */ 332 error = acquire(lkp, extflags, LK_WANT_UPGRADE | LK_SHARE_NONZERO); 333 lkp->lk_flags &= ~LK_WANT_EXCL; 334 if (error) 335 break; 336 lkp->lk_flags |= LK_HAVE_EXCL; 337 lkp->lk_lockholder = td; 338 if (lkp->lk_exclusivecount != 0) 339 panic("lockmgr: non-zero exclusive count"); 340 lkp->lk_exclusivecount = 1; 341 #if defined(DEBUG_LOCKS) 342 lkp->lk_filename = file; 343 lkp->lk_lineno = line; 344 lkp->lk_lockername = name; 345 #endif 346 COUNT(td, 1); 347 break; 348 349 case LK_RELEASE: 350 if (lkp->lk_exclusivecount != 0) { 351 if (lkp->lk_lockholder != td && 352 lkp->lk_lockholder != LK_KERNTHREAD) { 353 panic("lockmgr: pid %d, not %s thr %p unlocking", 354 (td->td_proc ? td->td_proc->p_pid : -99), 355 "exclusive lock holder", 356 lkp->lk_lockholder); 357 } 358 if (lkp->lk_lockholder != LK_KERNTHREAD) { 359 COUNT(td, -1); 360 } 361 if (lkp->lk_exclusivecount == 1) { 362 lkp->lk_flags &= ~LK_HAVE_EXCL; 363 lkp->lk_lockholder = LK_NOTHREAD; 364 lkp->lk_exclusivecount = 0; 365 } else { 366 lkp->lk_exclusivecount--; 367 } 368 } else if (lkp->lk_flags & LK_SHARE_NONZERO) { 369 shareunlock(lkp, 1); 370 COUNT(td, -1); 371 } 372 if (lkp->lk_flags & LK_WAIT_NONZERO) 373 wakeup((void *)lkp); 374 break; 375 376 case LK_DRAIN: 377 /* 378 * Check that we do not already hold the lock, as it can 379 * never drain if we do. Unfortunately, we have no way to 380 * check for holding a shared lock, but at least we can 381 * check for an exclusive one. 382 */ 383 if (lkp->lk_lockholder == td) 384 panic("lockmgr: draining against myself"); 385 386 error = acquiredrain(lkp, extflags); 387 if (error) 388 break; 389 lkp->lk_flags |= LK_DRAINING | LK_HAVE_EXCL; 390 lkp->lk_lockholder = td; 391 lkp->lk_exclusivecount = 1; 392 #if defined(DEBUG_LOCKS) 393 lkp->lk_filename = file; 394 lkp->lk_lineno = line; 395 lkp->lk_lockername = name; 396 #endif 397 COUNT(td, 1); 398 break; 399 400 default: 401 lwkt_reltoken(&lkp->lk_interlock); 402 panic("lockmgr: unknown locktype request %d", 403 flags & LK_TYPE_MASK); 404 /* NOTREACHED */ 405 } 406 if ((lkp->lk_flags & LK_WAITDRAIN) && 407 (lkp->lk_flags & (LK_HAVE_EXCL | LK_WANT_EXCL | LK_WANT_UPGRADE | 408 LK_SHARE_NONZERO | LK_WAIT_NONZERO)) == 0) { 409 lkp->lk_flags &= ~LK_WAITDRAIN; 410 wakeup((void *)&lkp->lk_flags); 411 } 412 lwkt_reltoken(&lkp->lk_interlock); 413 return (error); 414 } 415 416 static int 417 acquiredrain(struct lock *lkp, int extflags) 418 { 419 int error; 420 421 if ((extflags & LK_NOWAIT) && (lkp->lk_flags & LK_ALL)) { 422 return EBUSY; 423 } 424 425 if ((lkp->lk_flags & LK_ALL) == 0) 426 return 0; 427 428 while (lkp->lk_flags & LK_ALL) { 429 lkp->lk_flags |= LK_WAITDRAIN; 430 lwkt_reltoken(&lkp->lk_interlock); 431 error = tsleep(&lkp->lk_flags, lkp->lk_prio, 432 lkp->lk_wmesg, 433 ((extflags & LK_TIMELOCK) ? lkp->lk_timo : 0)); 434 lwkt_gettoken(&lkp->lk_interlock); 435 if (error) 436 return error; 437 if (extflags & LK_SLEEPFAIL) { 438 return ENOLCK; 439 } 440 } 441 return 0; 442 } 443 444 /* 445 * Initialize a lock; required before use. 446 */ 447 void 448 lockinit(lkp, prio, wmesg, timo, flags) 449 struct lock *lkp; 450 int prio; 451 char *wmesg; 452 int timo; 453 int flags; 454 { 455 lwkt_inittoken(&lkp->lk_interlock); 456 lkp->lk_flags = (flags & LK_EXTFLG_MASK); 457 lkp->lk_sharecount = 0; 458 lkp->lk_waitcount = 0; 459 lkp->lk_exclusivecount = 0; 460 lkp->lk_prio = prio; 461 lkp->lk_wmesg = wmesg; 462 lkp->lk_timo = timo; 463 lkp->lk_lockholder = LK_NOTHREAD; 464 } 465 466 /* 467 * Determine the status of a lock. 468 */ 469 int 470 lockstatus(struct lock *lkp, struct thread *td) 471 { 472 int lock_type = 0; 473 474 lwkt_gettoken(&lkp->lk_interlock); 475 if (lkp->lk_exclusivecount != 0) { 476 if (td == NULL || lkp->lk_lockholder == td) 477 lock_type = LK_EXCLUSIVE; 478 else 479 lock_type = LK_EXCLOTHER; 480 } else if (lkp->lk_sharecount != 0) { 481 lock_type = LK_SHARED; 482 } 483 lwkt_reltoken(&lkp->lk_interlock); 484 return (lock_type); 485 } 486 487 /* 488 * Determine the number of holders of a lock. 489 */ 490 int 491 lockcount(lkp) 492 struct lock *lkp; 493 { 494 int count; 495 496 lwkt_gettoken(&lkp->lk_interlock); 497 count = lkp->lk_exclusivecount + lkp->lk_sharecount; 498 lwkt_reltoken(&lkp->lk_interlock); 499 return (count); 500 } 501 502 /* 503 * Print out information about state of a lock. Used by VOP_PRINT 504 * routines to display status about contained locks. 505 */ 506 void 507 lockmgr_printinfo(lkp) 508 struct lock *lkp; 509 { 510 struct thread *td = lkp->lk_lockholder; 511 struct proc *p; 512 513 if (td && td != LK_KERNTHREAD && td != LK_NOTHREAD) 514 p = td->td_proc; 515 else 516 p = NULL; 517 518 if (lkp->lk_sharecount) 519 printf(" lock type %s: SHARED (count %d)", lkp->lk_wmesg, 520 lkp->lk_sharecount); 521 else if (lkp->lk_flags & LK_HAVE_EXCL) 522 printf(" lock type %s: EXCL (count %d) by td %p pid %d", 523 lkp->lk_wmesg, lkp->lk_exclusivecount, td, 524 p ? p->p_pid : -99); 525 if (lkp->lk_waitcount > 0) 526 printf(" with %d pending", lkp->lk_waitcount); 527 } 528 529