1 /* 2 * Copyright (c) 1995 3 * The Regents of the University of California. All rights reserved. 4 * Copyright (c) 2013-2017 5 * The DragonFly Project. 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 * This code is derived from software contributed to The DragonFly Project 12 * by Matthew Dillon <dillon@backplane.com> 13 * 14 * Redistribution and use in source and binary forms, with or without 15 * modification, are permitted provided that the following conditions 16 * are met: 17 * 1. Redistributions of source code must retain the above copyright 18 * notice, this list of conditions and the following disclaimer. 19 * 2. Redistributions in binary form must reproduce the above copyright 20 * notice, this list of conditions and the following disclaimer in the 21 * documentation and/or other materials provided with the distribution. 22 * 3. Neither the name of the University nor the names of its contributors 23 * may be used to endorse or promote products derived from this software 24 * without specific prior written permission. 25 * 26 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 27 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 28 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 29 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 30 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 31 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 32 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 33 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 34 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 35 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 36 * SUCH DAMAGE. 37 */ 38 39 #ifndef _SYS_LOCK_H_ 40 #define _SYS_LOCK_H_ 41 42 /* 43 * A number of third party programs #include <sys/lock.h> for no good 44 * reason. Don't actually include anything unless we are the kernel. 45 */ 46 #if defined(_KERNEL) || defined(_KERNEL_STRUCTURES) 47 48 #include <machine/lock.h> 49 #ifndef _SYS_THREAD_H_ 50 #include <sys/thread.h> /* lwkt_token */ 51 #endif 52 #ifndef _SYS_SPINLOCK_H_ 53 #include <sys/spinlock.h> 54 #endif 55 56 /* 57 * The general lock structure. Provides for multiple shared locks, 58 * upgrading from shared to exclusive, and sleeping until the lock 59 * can be gained. 60 * 61 * NOTE: We don't __cachealign struct lock, its too much bloat. Users 62 * of struct lock may be able to arrange it within greater structures 63 * in more SMP-friendly ways. 64 */ 65 struct thread; 66 67 struct lock { 68 u_int lk_flags; /* see below */ 69 int lk_timo; /* maximum sleep time (for tsleep) */ 70 uint64_t lk_count; /* see LKC_* bits */ 71 const char *lk_wmesg; /* resource sleeping (for tsleep) */ 72 struct thread *lk_lockholder; /* thread of excl lock holder */ 73 }; 74 75 /* 76 * Lock request types: 77 * 78 * LK_SHARED 79 * Get one of many possible shared locks. If a process holding an 80 * exclusive lock requests a shared lock, the exclusive lock(s) will 81 * be downgraded to shared locks. 82 * 83 * LK_EXCLUSIVE 84 * Stop further shared locks, when they are cleared, grant a pending 85 * upgrade if it exists, then grant an exclusive lock. Only one exclusive 86 * lock may exist at a time, except that a process holding an exclusive 87 * lock may get additional exclusive locks if it explicitly sets the 88 * LK_CANRECURSE flag in the lock request, or if the LK_CANRECURSE flag 89 * was set when the lock was initialized. 90 * 91 * LK_UPGRADE 92 * The process must hold a shared lock that it wants to have upgraded 93 * to an exclusive lock. Other processes may get exclusive access to 94 * the resource between the time that the upgrade is requested and the 95 * time that it is granted. 96 * 97 * LK_EXCLUPGRADE 98 * the process must hold a shared lock that it wants to have upgraded 99 * to an exclusive lock. If the request succeeds, no other processes 100 * will have gotten exclusive access to the resource between the time 101 * that the upgrade is requested and the time that it is granted. 102 * However, if another process has already requested an upgrade, the 103 * request will fail (see error returns below). 104 * 105 * LK_DOWNGRADE 106 * The process must hold an exclusive lock that it wants to have 107 * downgraded to a shared lock. If the process holds multiple (recursive) 108 * exclusive locks, they will all be downgraded to shared locks. 109 * 110 * LK_RELEASE 111 * Release one instance of a lock. 112 * 113 * LK_CANCEL_BEG 114 * The current exclusive lock holder can cancel any blocked lock requests, 115 * or any new requests, whos callers specified LK_CANCELABLE. They will 116 * receive a ENOLCK error code. Cancel beg/end does not stack. 117 * 118 * The cancel command stays in effect until the exclusive lock holder 119 * releases the last count on the lock or issues a LK_CANCEL_END command. 120 * 121 * LK_CANCEL_END 122 * The current exclusive lock holder can stop canceling new requests 123 * whos callers specify LK_CANCELABLE. The exclusive lock is maintained. 124 * 125 * Note that the last release of the exclusive lock will also 126 * automatically end cancel mode. 127 * 128 * 129 * --- 130 * 131 * LK_EXCLOTHER - return for lockstatus(). Used when another process 132 * holds the lock exclusively. 133 * 134 * These are flags that are passed to the lockmgr routine. 135 */ 136 #define LK_TYPE_MASK 0x0000000f /* type of lock sought */ 137 #define LK_SHARED 0x00000001 /* shared lock */ 138 #define LK_EXCLUSIVE 0x00000002 /* exclusive lock */ 139 #define LK_UPGRADE 0x00000003 /* shared-to-exclusive upgrade */ 140 #define LK_EXCLUPGRADE 0x00000004 /* first shared-to-exclusive upgrade */ 141 #define LK_DOWNGRADE 0x00000005 /* exclusive-to-shared downgrade */ 142 #define LK_RELEASE 0x00000006 /* release any type of lock */ 143 #define LK_WAITUPGRADE 0x00000007 144 #define LK_EXCLOTHER 0x00000008 /* other process holds lock */ 145 #define LK_CANCEL_BEG 0x00000009 /* cancel other requests */ 146 #define LK_CANCEL_END 0x0000000a /* stop canceling other requests */ 147 148 /* 149 * lk_count bit fields. 150 * 151 * Positive count is exclusive, negative count is shared. The count field 152 * must be large enough to accomodate all possible threads. 153 */ 154 #define LKC_RESERVED8 0x0000000080000000LU /* (DNU, insn optimization) */ 155 #define LKC_EXREQ 0x0000000040000000LU /* waiting for excl lock */ 156 #define LKC_SHARED 0x0000000020000000LU /* shared lock(s) granted */ 157 #define LKC_UPREQ 0x0000000010000000LU /* waiting for upgrade */ 158 #define LKC_EXREQ2 0x0000000008000000LU /* multi-wait for EXREQ */ 159 #define LKC_CANCEL 0x0000000004000000LU /* cancel in effect */ 160 #define LKC_XMASK 0x0000000003FFFFFFLU 161 #define LKC_SMASK 0xFFFFFFFF00000000LU 162 #define LKC_SCOUNT 0x0000000100000000LU 163 #define LKC_SSHIFT 32 164 165 /* 166 * External lock flags. 167 * 168 * The first three flags may be set in lock_init to set their mode permanently, 169 * or passed in as arguments to the lock manager. 170 */ 171 #define LK_EXTFLG_MASK 0x070000F0 /* mask of external flags */ 172 #define LK_NOWAIT 0x00000010 /* do not sleep to await lock */ 173 #define LK_SLEEPFAIL 0x00000020 /* sleep, then return failure */ 174 #define LK_CANRECURSE 0x00000040 /* allow recursive exclusive lock */ 175 #define LK_NOCOLLSTATS 0x00000080 /* v_lock_coll not applicable */ 176 #define LK_CANCELABLE 0x01000000 /* blocked caller can be canceled */ 177 #define LK_TIMELOCK 0x02000000 178 #define LK_PCATCH 0x04000000 /* timelocked with signal catching */ 179 180 /* 181 * Control flags 182 * 183 * Non-persistent external flags. 184 */ 185 #define LK_FAILRECLAIM 0x00010000 /* vn_lock: allowed to fail on reclaim */ 186 #define LK_RETRY 0x00020000 /* vn_lock: retry until locked */ 187 #define LK_UNUSED40000 0x00040000 188 #define LK_UNUSED80000 0x00080000 189 190 /* 191 * Lock return status. 192 * 193 * Successfully obtained locks return 0. Locks will always succeed 194 * unless one of the following is true: 195 * LK_FORCEUPGRADE is requested and some other process has already 196 * requested a lock upgrade (returns EBUSY). 197 * LK_WAIT is set and a sleep would be required (returns EBUSY). 198 * LK_SLEEPFAIL is set and a sleep was done (returns ENOLCK). 199 * PCATCH is set in lock priority and a signal arrives (returns 200 * either EINTR or ERESTART if system calls is to be restarted). 201 * Non-null lock timeout and timeout expires (returns EWOULDBLOCK). 202 * A failed lock attempt always returns a non-zero error value. No lock 203 * is held after an error return (in particular, a failed LK_UPGRADE 204 * or LK_FORCEUPGRADE will have released its shared access lock). 205 */ 206 207 /* 208 * Indicator that no process holds exclusive lock 209 */ 210 #define LK_KERNTHREAD ((struct thread *)-2) 211 212 #ifdef _KERNEL 213 214 void dumplockinfo(struct lock *lkp); 215 struct proc; 216 217 struct lock_args { 218 struct lock *la_lock; 219 const char *la_desc; 220 int la_flags; 221 }; 222 223 #define LOCK_INITIALIZER(wmesg, timo, flags) \ 224 { \ 225 .lk_flags = ((flags) & LK_EXTFLG_MASK), \ 226 .lk_timo = (timo), \ 227 .lk_count = 0, \ 228 .lk_wmesg = wmesg, \ 229 .lk_lockholder = NULL \ 230 } 231 232 void lockinit (struct lock *, const char *wmesg, int timo, int flags); 233 void lockreinit (struct lock *, const char *wmesg, int timo, int flags); 234 void lockuninit(struct lock *); 235 void lock_sysinit(struct lock_args *); 236 int lockmgr_shared (struct lock *, u_int flags); 237 int lockmgr_exclusive (struct lock *, u_int flags); 238 int lockmgr_downgrade (struct lock *, u_int flags); 239 int lockmgr_upgrade (struct lock *, u_int flags); 240 int lockmgr_release (struct lock *, u_int flags); 241 int lockmgr_cancel_beg (struct lock *, u_int flags); 242 int lockmgr_cancel_end (struct lock *, u_int flags); 243 void lockmgr_kernproc (struct lock *); 244 void lockmgr_printinfo (struct lock *); 245 int lockstatus (struct lock *, struct thread *); 246 int lockowned (struct lock *); 247 248 #define LOCK_SYSINIT(name, lock, desc, flags) \ 249 static struct lock_args name##_args = { \ 250 (lock), \ 251 (desc), \ 252 (flags) \ 253 }; \ 254 SYSINIT(name##_lock_sysinit, SI_SUB_DRIVERS, SI_ORDER_MIDDLE, \ 255 lock_sysinit, &name##_args); \ 256 SYSUNINIT(name##_lock_sysuninit, SI_SUB_DRIVERS, SI_ORDER_MIDDLE, \ 257 lockuninit, (lock)) 258 259 /* 260 * Most lockmgr() calls pass a constant flags parameter which 261 * we can optimize-out with an inline. 262 */ 263 static __inline 264 int 265 lockmgr(struct lock *lkp, u_int flags) 266 { 267 switch (flags & LK_TYPE_MASK) { 268 case LK_SHARED: 269 return lockmgr_shared(lkp, flags); 270 case LK_EXCLUSIVE: 271 return lockmgr_exclusive(lkp, flags); 272 case LK_DOWNGRADE: 273 return lockmgr_downgrade(lkp, flags); 274 case LK_EXCLUPGRADE: 275 case LK_UPGRADE: 276 return lockmgr_upgrade(lkp, flags); 277 case LK_RELEASE: 278 return lockmgr_release(lkp, flags); 279 case LK_CANCEL_BEG: 280 return lockmgr_cancel_beg(lkp, flags); 281 case LK_CANCEL_END: 282 return lockmgr_cancel_end(lkp, flags); 283 default: 284 panic("lockmgr: unknown locktype request %d", 285 flags & LK_TYPE_MASK); 286 return EINVAL; /* NOT REACHED */ 287 } 288 } 289 290 /* 291 * Returns non-zero if the lock is in-use. Cannot be used to count 292 * refs on a lock (refs cannot be safely counted due to the use of 293 * atomic_fetchadd_int() for shared locks. 294 */ 295 static __inline 296 int 297 lockinuse(struct lock *lkp) 298 { 299 return ((lkp->lk_count & (LKC_SMASK | LKC_XMASK)) != 0); 300 } 301 302 /* 303 * Returns true if the lock was acquired. Can be used to port 304 * FreeBSD's mtx_trylock() and similar functions. 305 */ 306 static __inline 307 boolean_t 308 lockmgr_try(struct lock *lkp, u_int flags) 309 { 310 return (lockmgr(lkp, flags | LK_NOWAIT) == 0); 311 } 312 313 /* 314 * Returns true if the lock is exclusively held by anyone 315 */ 316 static __inline 317 boolean_t 318 lockmgr_anyexcl(struct lock *lkp) 319 { 320 return ((lkp->lk_count & LKC_XMASK) != 0); 321 } 322 323 static __inline 324 boolean_t 325 lockmgr_oneexcl(struct lock *lkp) 326 { 327 return ((lkp->lk_count & LKC_XMASK) == 1); 328 } 329 330 static __inline 331 boolean_t 332 lockmgr_exclpending(struct lock *lkp) 333 { 334 return ((lkp->lk_count & (LKC_EXREQ | LKC_EXREQ2)) != 0); 335 } 336 337 #endif /* _KERNEL */ 338 #endif /* _KERNEL || _KERNEL_STRUCTURES */ 339 #endif /* _SYS_LOCK_H_ */ 340