sx.h revision 168191
1/*- 2 * Copyright (c) 2007 Attilio Rao <attilio@freebsd.org> 3 * Copyright (c) 2001 Jason Evans <jasone@freebsd.org> 4 * All rights reserved. 5 * 6 * Redistribution and use in source and binary forms, with or without 7 * modification, are permitted provided that the following conditions 8 * are met: 9 * 1. Redistributions of source code must retain the above copyright 10 * notice(s), this list of conditions and the following disclaimer as 11 * the first lines of this file unmodified other than the possible 12 * addition of one or more copyright notices. 13 * 2. Redistributions in binary form must reproduce the above copyright 14 * notice(s), this list of conditions and the following disclaimer in the 15 * documentation and/or other materials provided with the distribution. 16 * 17 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER(S) ``AS IS'' AND ANY 18 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED 19 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE 20 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER(S) BE LIABLE FOR ANY 21 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES 22 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR 23 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER 24 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH 27 * DAMAGE. 28 * 29 * $FreeBSD: head/sys/sys/sx.h 168191 2007-03-31 23:23:42Z jhb $ 30 */ 31 32#ifndef _SYS_SX_H_ 33#define _SYS_SX_H_ 34 35#include <sys/_lock.h> 36#include <sys/_sx.h> 37 38#ifdef _KERNEL 39#include <machine/atomic.h> 40#endif 41 42/* 43 * In general, the sx locks and rwlocks use very similar algorithms. 44 * The main difference in the implementations is how threads are 45 * blocked when a lock is unavailable. For this, sx locks use sleep 46 * queues which do not support priority propagation, and rwlocks use 47 * turnstiles which do. 48 * 49 * The sx_lock field consists of several fields. The low bit 50 * indicates if the lock is locked with a shared or exclusive lock. A 51 * value of 0 indicates an exclusive lock, and a value of 1 indicates 52 * a shared lock. Bit 1 is a boolean indicating if there are any 53 * threads waiting for a shared lock. Bit 2 is a boolean indicating 54 * if there are any threads waiting for an exclusive lock. Bit 3 is a 55 * boolean indicating if an exclusive lock is recursively held. The 56 * rest of the variable's definition is dependent on the value of the 57 * first bit. For an exclusive lock, it is a pointer to the thread 58 * holding the lock, similar to the mtx_lock field of mutexes. For 59 * shared locks, it is a count of read locks that are held. 60 * 61 * When the lock is not locked by any thread, it is encoded as a 62 * shared lock with zero waiters. 63 * 64 * A note about memory barriers. Exclusive locks need to use the same 65 * memory barriers as mutexes: _acq when acquiring an exclusive lock 66 * and _rel when releasing an exclusive lock. On the other side, 67 * shared lock needs to use an _acq barrier when acquiring the lock 68 * but, since they don't update any locked data, no memory barrier is 69 * needed when releasing a shared lock. 70 */ 71 72#define SX_LOCK_SHARED 0x01 73#define SX_LOCK_SHARED_WAITERS 0x02 74#define SX_LOCK_EXCLUSIVE_WAITERS 0x04 75#define SX_LOCK_RECURSED 0x08 76#define SX_LOCK_FLAGMASK \ 77 (SX_LOCK_SHARED | SX_LOCK_SHARED_WAITERS | \ 78 SX_LOCK_EXCLUSIVE_WAITERS | SX_LOCK_RECURSED) 79 80#define SX_OWNER(x) ((x) & ~SX_LOCK_FLAGMASK) 81#define SX_SHARERS_SHIFT 4 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 89#ifdef _KERNEL 90 91/* 92 * Full lock operations that are suitable to be inlined in non-debug kernels. 93 * If the lock can't be acquired or released trivially then the work is 94 * deferred to 'tougher' functions. 95 */ 96 97/* Acquire an exclusive lock. */ 98#define __sx_xlock(sx, tid, file, line) do { \ 99 uintptr_t _tid = (uintptr_t)(tid); \ 100 int contested = 0; \ 101 uint64_t waitstart = 0; \ 102 \ 103 if (!atomic_cmpset_acq_ptr(&(sx)->sx_lock, SX_LOCK_UNLOCKED, \ 104 _tid)) { \ 105 lock_profile_obtain_lock_failed(&(sx)->lock_object, \ 106 &contested, &waitstart); \ 107 _sx_xlock_hard((sx), _tid, (file), (line)); \ 108 } \ 109 lock_profile_obtain_lock_success(&(sx)->lock_object, contested, \ 110 waitstart, (file), (line)); \ 111} while (0) 112 113/* Release an exclusive lock. */ 114#define __sx_xunlock(sx, tid, file, line) do { \ 115 uintptr_t _tid = (uintptr_t)(tid); \ 116 \ 117 if (!atomic_cmpset_rel_ptr(&(sx)->sx_lock, _tid, \ 118 SX_LOCK_UNLOCKED)) \ 119 _sx_xunlock_hard((sx), _tid, (file), (line)); \ 120} while (0) 121 122/* Acquire a shared lock. */ 123#define __sx_slock(sx, file, line) do { \ 124 uintptr_t x = (sx)->sx_lock; \ 125 int contested = 0; \ 126 uint64_t waitstart = 0; \ 127 \ 128 if (!(x & SX_LOCK_SHARED) || \ 129 !atomic_cmpset_acq_ptr(&(sx)->sx_lock, x, \ 130 x + SX_ONE_SHARER)) { \ 131 lock_profile_obtain_lock_failed(&(sx)->lock_object, \ 132 &contested, &waitstart); \ 133 _sx_slock_hard((sx), (file), (line)); \ 134 } \ 135 lock_profile_obtain_lock_success(&(sx)->lock_object, contested, \ 136 waitstart, (file), (line)); \ 137} while (0) 138 139/* 140 * Release a shared lock. We can just drop a single shared lock so 141 * long as we aren't trying to drop the last shared lock when other 142 * threads are waiting for an exclusive lock. This takes advantage of 143 * the fact that an unlocked lock is encoded as a shared lock with a 144 * count of 0. 145 */ 146#define __sx_sunlock(sx, file, line) do { \ 147 uintptr_t x = (sx)->sx_lock; \ 148 \ 149 if (x == (SX_SHARERS_LOCK(1) | SX_LOCK_EXCLUSIVE_WAITERS) || \ 150 !atomic_cmpset_ptr(&(sx)->sx_lock, x, x - SX_ONE_SHARER)) \ 151 _sx_sunlock_hard((sx), (file), (line)); \ 152} while (0) 153 154/* 155 * Function prototipes. Routines that start with an underscore are not part 156 * of the public interface and are wrappered with a macro. 157 */ 158void sx_sysinit(void *arg); 159#define sx_init(sx, desc) sx_init_flags((sx), (desc), 0) 160void sx_init_flags(struct sx *sx, const char *description, int opts); 161void sx_destroy(struct sx *sx); 162void _sx_slock(struct sx *sx, const char *file, int line); 163void _sx_xlock(struct sx *sx, const char *file, int line); 164int _sx_try_slock(struct sx *sx, const char *file, int line); 165int _sx_try_xlock(struct sx *sx, const char *file, int line); 166void _sx_sunlock(struct sx *sx, const char *file, int line); 167void _sx_xunlock(struct sx *sx, const char *file, int line); 168int _sx_try_upgrade(struct sx *sx, const char *file, int line); 169void _sx_downgrade(struct sx *sx, const char *file, int line); 170void _sx_xlock_hard(struct sx *sx, uintptr_t tid, const char *file, int 171 line); 172void _sx_slock_hard(struct sx *sx, const char *file, int line); 173void _sx_xunlock_hard(struct sx *sx, uintptr_t tid, const char *file, int 174 line); 175void _sx_sunlock_hard(struct sx *sx, const char *file, int line); 176#if defined(INVARIANTS) || defined(INVARIANT_SUPPORT) 177void _sx_assert(struct sx *sx, int what, const char *file, int line); 178#endif 179#ifdef DDB 180int sx_chain(struct thread *td, struct thread **ownerp); 181#endif 182 183struct sx_args { 184 struct sx *sa_sx; 185 const char *sa_desc; 186}; 187 188#define SX_SYSINIT(name, sxa, desc) \ 189 static struct sx_args name##_args = { \ 190 (sxa), \ 191 (desc) \ 192 }; \ 193 SYSINIT(name##_sx_sysinit, SI_SUB_LOCK, SI_ORDER_MIDDLE, \ 194 sx_sysinit, &name##_args); \ 195 SYSUNINIT(name##_sx_sysuninit, SI_SUB_LOCK, SI_ORDER_MIDDLE, \ 196 sx_destroy, (sxa)) 197 198/* 199 * Public interface for lock operations. 200 */ 201#ifndef LOCK_DEBUG 202#error "LOCK_DEBUG not defined, include <sys/lock.h> before <sys/sx.h>" 203#endif 204#if (LOCK_DEBUG > 0) || defined(SX_NOINLINE) 205#define sx_xlock(sx) _sx_xlock((sx), LOCK_FILE, LOCK_LINE) 206#define sx_xunlock(sx) _sx_xunlock((sx), LOCK_FILE, LOCK_LINE) 207#define sx_slock(sx) _sx_slock((sx), LOCK_FILE, LOCK_LINE) 208#define sx_sunlock(sx) _sx_sunlock((sx), LOCK_FILE, LOCK_LINE) 209#else 210#define sx_xlock(sx) \ 211 __sx_xlock((sx), curthread, LOCK_FILE, LOCK_LINE) 212#define sx_xunlock(sx) \ 213 __sx_xunlock((sx), curthread, LOCK_FILE, LOCK_LINE) 214#define sx_slock(sx) __sx_slock((sx), LOCK_FILE, LOCK_LINE) 215#define sx_sunlock(sx) __sx_sunlock((sx), LOCK_FILE, LOCK_LINE) 216#endif /* LOCK_DEBUG > 0 || SX_NOINLINE */ 217#define sx_try_slock(sx) _sx_try_slock((sx), LOCK_FILE, LOCK_LINE) 218#define sx_try_xlock(sx) _sx_try_xlock((sx), LOCK_FILE, LOCK_LINE) 219#define sx_try_upgrade(sx) _sx_try_upgrade((sx), LOCK_FILE, LOCK_LINE) 220#define sx_downgrade(sx) _sx_downgrade((sx), LOCK_FILE, LOCK_LINE) 221 222#define sx_xlocked(sx) \ 223 (((sx)->sx_lock & ~(SX_LOCK_FLAGMASK & ~SX_LOCK_SHARED)) == \ 224 (uintptr_t)curthread) 225 226#define sx_unlock(sx) do { \ 227 if (sx_xlocked(sx)) \ 228 sx_xunlock(sx); \ 229 else \ 230 sx_sunlock(sx); \ 231} while (0) 232 233#define sx_sleep(chan, sx, pri, wmesg, timo) \ 234 _sleep((chan), &(sx)->lock_object, (pri), (wmesg), (timo)) 235 236/* 237 * Options passed to sx_init_flags(). 238 */ 239#define SX_DUPOK 0x01 240#define SX_NOPROFILE 0x02 241#define SX_NOWITNESS 0x04 242#define SX_QUIET 0x08 243#define SX_ADAPTIVESPIN 0x10 244 245/* 246 * XXX: These options should be renamed as SA_* 247 */ 248#if defined(INVARIANTS) || defined(INVARIANT_SUPPORT) 249#define SX_LOCKED LA_LOCKED 250#define SX_SLOCKED LA_SLOCKED 251#define SX_XLOCKED LA_XLOCKED 252#define SX_UNLOCKED LA_UNLOCKED 253#define SX_RECURSED LA_RECURSED 254#define SX_NOTRECURSED LA_NOTRECURSED 255#endif 256 257#ifdef INVARIANTS 258#define sx_assert(sx, what) _sx_assert((sx), (what), LOCK_FILE, LOCK_LINE) 259#else 260#define sx_assert(sx, what) 261#endif 262 263#endif /* _KERNEL */ 264 265#endif /* !_SYS_SX_H_ */ 266