1/*- 2 * SPDX-License-Identifier: BSD-2-Clause-FreeBSD 3 * 4 * Copyright (c) 2007 Attilio Rao <attilio@freebsd.org> 5 * Copyright (c) 2001 Jason Evans <jasone@freebsd.org> 6 * All rights reserved. 7 * 8 * Redistribution and use in source and binary forms, with or without 9 * modification, are permitted provided that the following conditions 10 * are met: 11 * 1. Redistributions of source code must retain the above copyright 12 * notice(s), this list of conditions and the following disclaimer as 13 * the first lines of this file unmodified other than the possible 14 * addition of one or more copyright notices. 15 * 2. Redistributions in binary form must reproduce the above copyright 16 * notice(s), this list of conditions and the following disclaimer in the 17 * documentation and/or other materials provided with the distribution. 18 * 19 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER(S) ``AS IS'' AND ANY 20 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED 21 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE 22 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER(S) BE LIABLE FOR ANY 23 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES 24 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR 25 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER 26 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 27 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 28 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH 29 * DAMAGE. 30 * 31 * $FreeBSD$ 32 */ 33 34#ifndef _SYS_SX_H_ 35#define _SYS_SX_H_ 36 37#include <sys/_lock.h> 38#include <sys/_sx.h> 39 40#ifdef _KERNEL 41#include <sys/pcpu.h> 42#include <sys/lock_profile.h> 43#include <sys/lockstat.h> 44#include <machine/atomic.h> 45#endif 46 47/* 48 * In general, the sx locks and rwlocks use very similar algorithms. 49 * The main difference in the implementations is how threads are 50 * blocked when a lock is unavailable. For this, sx locks use sleep 51 * queues which do not support priority propagation, and rwlocks use 52 * turnstiles which do. 53 * 54 * The sx_lock field consists of several fields. The low bit 55 * indicates if the lock is locked with a shared or exclusive lock. A 56 * value of 0 indicates an exclusive lock, and a value of 1 indicates 57 * a shared lock. Bit 1 is a boolean indicating if there are any 58 * threads waiting for a shared lock. Bit 2 is a boolean indicating 59 * if there are any threads waiting for an exclusive lock. Bit 3 is a 60 * boolean indicating if an exclusive lock is recursively held. The 61 * rest of the variable's definition is dependent on the value of the 62 * first bit. For an exclusive lock, it is a pointer to the thread 63 * holding the lock, similar to the mtx_lock field of mutexes. For 64 * shared locks, it is a count of read locks that are held. 65 * 66 * When the lock is not locked by any thread, it is encoded as a 67 * shared lock with zero waiters. 68 */ 69 70#define SX_LOCK_SHARED 0x01 71#define SX_LOCK_SHARED_WAITERS 0x02 72#define SX_LOCK_EXCLUSIVE_WAITERS 0x04 73#define SX_LOCK_WRITE_SPINNER 0x08 74#define SX_LOCK_RECURSED 0x10 75#define SX_LOCK_FLAGMASK \ 76 (SX_LOCK_SHARED | SX_LOCK_SHARED_WAITERS | \ 77 SX_LOCK_EXCLUSIVE_WAITERS | SX_LOCK_RECURSED | SX_LOCK_WRITE_SPINNER) 78#define SX_LOCK_WAITERS (SX_LOCK_SHARED_WAITERS | SX_LOCK_EXCLUSIVE_WAITERS) 79 80#define SX_OWNER(x) ((x) & ~SX_LOCK_FLAGMASK) 81#define SX_SHARERS_SHIFT 5 82#define SX_SHARERS(x) (SX_OWNER(x) >> SX_SHARERS_SHIFT) 83#define SX_SHARERS_LOCK(x) \ 84 ((x) << SX_SHARERS_SHIFT | SX_LOCK_SHARED) 85#define SX_ONE_SHARER (1 << SX_SHARERS_SHIFT) 86 87#define SX_LOCK_UNLOCKED SX_SHARERS_LOCK(0) 88#define SX_LOCK_DESTROYED \ 89 (SX_LOCK_SHARED_WAITERS | SX_LOCK_EXCLUSIVE_WAITERS) 90 91#ifdef _KERNEL 92 93#define sx_recurse lock_object.lo_data 94 95#define SX_READ_VALUE(sx) ((sx)->sx_lock) 96 97#define lv_sx_owner(v) \ 98 ((v & SX_LOCK_SHARED) ? NULL : (struct thread *)SX_OWNER(v)) 99 100/* 101 * Function prototipes. Routines that start with an underscore are not part 102 * of the public interface and are wrappered with a macro. 103 */ 104void sx_sysinit(void *arg); 105#define sx_init(sx, desc) sx_init_flags((sx), (desc), 0) 106void sx_init_flags(struct sx *sx, const char *description, int opts); 107void sx_destroy(struct sx *sx); 108int sx_try_slock_int(struct sx *sx LOCK_FILE_LINE_ARG_DEF); 109int sx_try_slock_(struct sx *sx, const char *file, int line); 110int sx_try_xlock_int(struct sx *sx LOCK_FILE_LINE_ARG_DEF); 111int sx_try_xlock_(struct sx *sx, const char *file, int line); 112int sx_try_upgrade_int(struct sx *sx LOCK_FILE_LINE_ARG_DEF); 113int sx_try_upgrade_(struct sx *sx, const char *file, int line); 114void sx_downgrade_int(struct sx *sx LOCK_FILE_LINE_ARG_DEF); 115void sx_downgrade_(struct sx *sx, const char *file, int line); 116int _sx_slock_int(struct sx *sx, int opts LOCK_FILE_LINE_ARG_DEF); 117int _sx_slock(struct sx *sx, int opts, const char *file, int line); 118int _sx_xlock(struct sx *sx, int opts, const char *file, int line); 119void _sx_sunlock_int(struct sx *sx LOCK_FILE_LINE_ARG_DEF); 120void _sx_sunlock(struct sx *sx, const char *file, int line); 121void _sx_xunlock(struct sx *sx, const char *file, int line); 122int _sx_xlock_hard(struct sx *sx, uintptr_t x, int opts LOCK_FILE_LINE_ARG_DEF); 123void _sx_xunlock_hard(struct sx *sx, uintptr_t x LOCK_FILE_LINE_ARG_DEF); 124#if defined(INVARIANTS) || defined(INVARIANT_SUPPORT) 125void _sx_assert(const struct sx *sx, int what, const char *file, int line); 126#endif 127#ifdef DDB 128int sx_chain(struct thread *td, struct thread **ownerp); 129#endif 130 131struct sx_args { 132 struct sx *sa_sx; 133 const char *sa_desc; 134 int sa_flags; 135}; 136 137#define SX_SYSINIT_FLAGS(name, sxa, desc, flags) \ 138 static struct sx_args name##_args = { \ 139 (sxa), \ 140 (desc), \ 141 (flags) \ 142 }; \ 143 SYSINIT(name##_sx_sysinit, SI_SUB_LOCK, SI_ORDER_MIDDLE, \ 144 sx_sysinit, &name##_args); \ 145 SYSUNINIT(name##_sx_sysuninit, SI_SUB_LOCK, SI_ORDER_MIDDLE, \ 146 sx_destroy, (sxa)) 147 148#define SX_SYSINIT(name, sxa, desc) SX_SYSINIT_FLAGS(name, sxa, desc, 0) 149 150/* 151 * Full lock operations that are suitable to be inlined in non-debug kernels. 152 * If the lock can't be acquired or released trivially then the work is 153 * deferred to 'tougher' functions. 154 */ 155 156#if (LOCK_DEBUG == 0) 157/* Acquire an exclusive lock. */ 158static __inline int 159__sx_xlock(struct sx *sx, struct thread *td, int opts, const char *file, 160 int line) 161{ 162 uintptr_t tid = (uintptr_t)td; 163 uintptr_t v = SX_LOCK_UNLOCKED; 164 int error = 0; 165 166 if (__predict_false(LOCKSTAT_PROFILE_ENABLED(sx__acquire) || 167 !atomic_fcmpset_acq_ptr(&sx->sx_lock, &v, tid))) 168 error = _sx_xlock_hard(sx, v, opts); 169 170 return (error); 171} 172 173/* Release an exclusive lock. */ 174static __inline void 175__sx_xunlock(struct sx *sx, struct thread *td, const char *file, int line) 176{ 177 uintptr_t x = (uintptr_t)td; 178 179 if (__predict_false(LOCKSTAT_PROFILE_ENABLED(sx__release) || 180 !atomic_fcmpset_rel_ptr(&sx->sx_lock, &x, SX_LOCK_UNLOCKED))) 181 _sx_xunlock_hard(sx, x); 182} 183#endif 184 185/* 186 * Public interface for lock operations. 187 */ 188#ifndef LOCK_DEBUG 189#error "LOCK_DEBUG not defined, include <sys/lock.h> before <sys/sx.h>" 190#endif 191#if (LOCK_DEBUG > 0) || defined(SX_NOINLINE) 192#define sx_xlock_(sx, file, line) \ 193 (void)_sx_xlock((sx), 0, (file), (line)) 194#define sx_xlock_sig_(sx, file, line) \ 195 _sx_xlock((sx), SX_INTERRUPTIBLE, (file), (line)) 196#define sx_xunlock_(sx, file, line) \ 197 _sx_xunlock((sx), (file), (line)) 198#else 199#define sx_xlock_(sx, file, line) \ 200 (void)__sx_xlock((sx), curthread, 0, (file), (line)) 201#define sx_xlock_sig_(sx, file, line) \ 202 __sx_xlock((sx), curthread, SX_INTERRUPTIBLE, (file), (line)) 203#define sx_xunlock_(sx, file, line) \ 204 __sx_xunlock((sx), curthread, (file), (line)) 205#endif /* LOCK_DEBUG > 0 || SX_NOINLINE */ 206#if (LOCK_DEBUG > 0) 207#define sx_slock_(sx, file, line) \ 208 (void)_sx_slock((sx), 0, (file), (line)) 209#define sx_slock_sig_(sx, file, line) \ 210 _sx_slock((sx), SX_INTERRUPTIBLE, (file) , (line)) 211#define sx_sunlock_(sx, file, line) \ 212 _sx_sunlock((sx), (file), (line)) 213#define sx_try_slock(sx) sx_try_slock_((sx), LOCK_FILE, LOCK_LINE) 214#define sx_try_xlock(sx) sx_try_xlock_((sx), LOCK_FILE, LOCK_LINE) 215#define sx_try_upgrade(sx) sx_try_upgrade_((sx), LOCK_FILE, LOCK_LINE) 216#define sx_downgrade(sx) sx_downgrade_((sx), LOCK_FILE, LOCK_LINE) 217#else 218#define sx_slock_(sx, file, line) \ 219 (void)_sx_slock_int((sx), 0) 220#define sx_slock_sig_(sx, file, line) \ 221 _sx_slock_int((sx), SX_INTERRUPTIBLE) 222#define sx_sunlock_(sx, file, line) \ 223 _sx_sunlock_int((sx)) 224#define sx_try_slock(sx) sx_try_slock_int((sx)) 225#define sx_try_xlock(sx) sx_try_xlock_int((sx)) 226#define sx_try_upgrade(sx) sx_try_upgrade_int((sx)) 227#define sx_downgrade(sx) sx_downgrade_int((sx)) 228#endif 229#ifdef INVARIANTS 230#define sx_assert_(sx, what, file, line) \ 231 _sx_assert((sx), (what), (file), (line)) 232#else 233#define sx_assert_(sx, what, file, line) (void)0 234#endif 235 236#define sx_xlock(sx) sx_xlock_((sx), LOCK_FILE, LOCK_LINE) 237#define sx_xlock_sig(sx) sx_xlock_sig_((sx), LOCK_FILE, LOCK_LINE) 238#define sx_xunlock(sx) sx_xunlock_((sx), LOCK_FILE, LOCK_LINE) 239#define sx_slock(sx) sx_slock_((sx), LOCK_FILE, LOCK_LINE) 240#define sx_slock_sig(sx) sx_slock_sig_((sx), LOCK_FILE, LOCK_LINE) 241#define sx_sunlock(sx) sx_sunlock_((sx), LOCK_FILE, LOCK_LINE) 242#define sx_assert(sx, what) sx_assert_((sx), (what), __FILE__, __LINE__) 243 244/* 245 * Return a pointer to the owning thread if the lock is exclusively 246 * locked. 247 */ 248#define sx_xholder(sx) \ 249 ((sx)->sx_lock & SX_LOCK_SHARED ? NULL : \ 250 (struct thread *)SX_OWNER((sx)->sx_lock)) 251 252#define sx_xlocked(sx) \ 253 (((sx)->sx_lock & ~(SX_LOCK_FLAGMASK & ~SX_LOCK_SHARED)) == \ 254 (uintptr_t)curthread) 255 256#define sx_unlock_(sx, file, line) do { \ 257 if (sx_xlocked(sx)) \ 258 sx_xunlock_(sx, file, line); \ 259 else \ 260 sx_sunlock_(sx, file, line); \ 261} while (0) 262 263#define sx_unlock(sx) sx_unlock_((sx), LOCK_FILE, LOCK_LINE) 264 265#define sx_sleep(chan, sx, pri, wmesg, timo) \ 266 _sleep((chan), &(sx)->lock_object, (pri), (wmesg), \ 267 tick_sbt * (timo), 0, C_HARDCLOCK) 268 269/* 270 * Options passed to sx_init_flags(). 271 */ 272#define SX_DUPOK 0x01 273#define SX_NOPROFILE 0x02 274#define SX_NOWITNESS 0x04 275#define SX_QUIET 0x08 276#define SX_RECURSE 0x20 277#define SX_NEW 0x40 278 279/* 280 * Options passed to sx_*lock_hard(). 281 */ 282#define SX_INTERRUPTIBLE 0x40 283 284#if defined(INVARIANTS) || defined(INVARIANT_SUPPORT) 285#define SA_LOCKED LA_LOCKED 286#define SA_SLOCKED LA_SLOCKED 287#define SA_XLOCKED LA_XLOCKED 288#define SA_UNLOCKED LA_UNLOCKED 289#define SA_RECURSED LA_RECURSED 290#define SA_NOTRECURSED LA_NOTRECURSED 291 292/* Backwards compatibility. */ 293#define SX_LOCKED LA_LOCKED 294#define SX_SLOCKED LA_SLOCKED 295#define SX_XLOCKED LA_XLOCKED 296#define SX_UNLOCKED LA_UNLOCKED 297#define SX_RECURSED LA_RECURSED 298#define SX_NOTRECURSED LA_NOTRECURSED 299#endif 300 301#endif /* _KERNEL */ 302 303#ifdef _STANDALONE 304/* since we have no threads in the boot loader, trivially implement no-op version */ 305#define sx_xlock(s) (1) 306#define sx_try_xlock(s) (1) 307#define sx_xunlock(s) (1) 308#define SX_DUPOK 0 309#define SX_NEW 0 310#define SX_NOWITNESS 0 311 312static __inline void 313sx_init_flags(struct sx *sx, const char *description, int opts) 314{ 315 316} 317 318static __inline void 319sx_destroy(struct sx *sx) 320{ 321 322} 323#endif /* _STANDALONE */ 324 325#endif /* !_SYS_SX_H_ */ 326