sx.h revision 168191
1139825Simp/*- 2168191Sjhb * Copyright (c) 2007 Attilio Rao <attilio@freebsd.org> 3168191Sjhb * Copyright (c) 2001 Jason Evans <jasone@freebsd.org> 4168191Sjhb * All rights reserved. 573782Sjasone * 673782Sjasone * Redistribution and use in source and binary forms, with or without 773782Sjasone * modification, are permitted provided that the following conditions 873782Sjasone * are met: 973782Sjasone * 1. Redistributions of source code must retain the above copyright 1073782Sjasone * notice(s), this list of conditions and the following disclaimer as 1173782Sjasone * the first lines of this file unmodified other than the possible 1273782Sjasone * addition of one or more copyright notices. 1373782Sjasone * 2. Redistributions in binary form must reproduce the above copyright 1473782Sjasone * notice(s), this list of conditions and the following disclaimer in the 1573782Sjasone * documentation and/or other materials provided with the distribution. 1673782Sjasone * 1773782Sjasone * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER(S) ``AS IS'' AND ANY 1873782Sjasone * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED 1973782Sjasone * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE 2073782Sjasone * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER(S) BE LIABLE FOR ANY 2173782Sjasone * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES 2273782Sjasone * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR 2373782Sjasone * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER 2473782Sjasone * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 2573782Sjasone * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 2673782Sjasone * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH 2773782Sjasone * DAMAGE. 2873782Sjasone * 2973782Sjasone * $FreeBSD: head/sys/sys/sx.h 168191 2007-03-31 23:23:42Z jhb $ 3073782Sjasone */ 3173782Sjasone 3273782Sjasone#ifndef _SYS_SX_H_ 3373782Sjasone#define _SYS_SX_H_ 3473782Sjasone 3583103Sjhb#include <sys/_lock.h> 36168191Sjhb#include <sys/_sx.h> 3773782Sjasone 38168191Sjhb#ifdef _KERNEL 39168191Sjhb#include <machine/atomic.h> 40168191Sjhb#endif 4173782Sjasone 42168191Sjhb/* 43168191Sjhb * In general, the sx locks and rwlocks use very similar algorithms. 44168191Sjhb * The main difference in the implementations is how threads are 45168191Sjhb * blocked when a lock is unavailable. For this, sx locks use sleep 46168191Sjhb * queues which do not support priority propagation, and rwlocks use 47168191Sjhb * turnstiles which do. 48168191Sjhb * 49168191Sjhb * The sx_lock field consists of several fields. The low bit 50168191Sjhb * indicates if the lock is locked with a shared or exclusive lock. A 51168191Sjhb * value of 0 indicates an exclusive lock, and a value of 1 indicates 52168191Sjhb * a shared lock. Bit 1 is a boolean indicating if there are any 53168191Sjhb * threads waiting for a shared lock. Bit 2 is a boolean indicating 54168191Sjhb * if there are any threads waiting for an exclusive lock. Bit 3 is a 55168191Sjhb * boolean indicating if an exclusive lock is recursively held. The 56168191Sjhb * rest of the variable's definition is dependent on the value of the 57168191Sjhb * first bit. For an exclusive lock, it is a pointer to the thread 58168191Sjhb * holding the lock, similar to the mtx_lock field of mutexes. For 59168191Sjhb * shared locks, it is a count of read locks that are held. 60168191Sjhb * 61168191Sjhb * When the lock is not locked by any thread, it is encoded as a 62168191Sjhb * shared lock with zero waiters. 63168191Sjhb * 64168191Sjhb * A note about memory barriers. Exclusive locks need to use the same 65168191Sjhb * memory barriers as mutexes: _acq when acquiring an exclusive lock 66168191Sjhb * and _rel when releasing an exclusive lock. On the other side, 67168191Sjhb * shared lock needs to use an _acq barrier when acquiring the lock 68168191Sjhb * but, since they don't update any locked data, no memory barrier is 69168191Sjhb * needed when releasing a shared lock. 70168191Sjhb */ 71168191Sjhb 72168191Sjhb#define SX_LOCK_SHARED 0x01 73168191Sjhb#define SX_LOCK_SHARED_WAITERS 0x02 74168191Sjhb#define SX_LOCK_EXCLUSIVE_WAITERS 0x04 75168191Sjhb#define SX_LOCK_RECURSED 0x08 76168191Sjhb#define SX_LOCK_FLAGMASK \ 77168191Sjhb (SX_LOCK_SHARED | SX_LOCK_SHARED_WAITERS | \ 78168191Sjhb SX_LOCK_EXCLUSIVE_WAITERS | SX_LOCK_RECURSED) 79168191Sjhb 80168191Sjhb#define SX_OWNER(x) ((x) & ~SX_LOCK_FLAGMASK) 81168191Sjhb#define SX_SHARERS_SHIFT 4 82168191Sjhb#define SX_SHARERS(x) (SX_OWNER(x) >> SX_SHARERS_SHIFT) 83168191Sjhb#define SX_SHARERS_LOCK(x) \ 84168191Sjhb ((x) << SX_SHARERS_SHIFT | SX_LOCK_SHARED) 85168191Sjhb#define SX_ONE_SHARER (1 << SX_SHARERS_SHIFT) 86168191Sjhb 87168191Sjhb#define SX_LOCK_UNLOCKED SX_SHARERS_LOCK(0) 88168191Sjhb 8973782Sjasone#ifdef _KERNEL 90168191Sjhb 91168191Sjhb/* 92168191Sjhb * Full lock operations that are suitable to be inlined in non-debug kernels. 93168191Sjhb * If the lock can't be acquired or released trivially then the work is 94168191Sjhb * deferred to 'tougher' functions. 95168191Sjhb */ 96168191Sjhb 97168191Sjhb/* Acquire an exclusive lock. */ 98168191Sjhb#define __sx_xlock(sx, tid, file, line) do { \ 99168191Sjhb uintptr_t _tid = (uintptr_t)(tid); \ 100168191Sjhb int contested = 0; \ 101168191Sjhb uint64_t waitstart = 0; \ 102168191Sjhb \ 103168191Sjhb if (!atomic_cmpset_acq_ptr(&(sx)->sx_lock, SX_LOCK_UNLOCKED, \ 104168191Sjhb _tid)) { \ 105168191Sjhb lock_profile_obtain_lock_failed(&(sx)->lock_object, \ 106168191Sjhb &contested, &waitstart); \ 107168191Sjhb _sx_xlock_hard((sx), _tid, (file), (line)); \ 108168191Sjhb } \ 109168191Sjhb lock_profile_obtain_lock_success(&(sx)->lock_object, contested, \ 110168191Sjhb waitstart, (file), (line)); \ 111168191Sjhb} while (0) 112168191Sjhb 113168191Sjhb/* Release an exclusive lock. */ 114168191Sjhb#define __sx_xunlock(sx, tid, file, line) do { \ 115168191Sjhb uintptr_t _tid = (uintptr_t)(tid); \ 116168191Sjhb \ 117168191Sjhb if (!atomic_cmpset_rel_ptr(&(sx)->sx_lock, _tid, \ 118168191Sjhb SX_LOCK_UNLOCKED)) \ 119168191Sjhb _sx_xunlock_hard((sx), _tid, (file), (line)); \ 120168191Sjhb} while (0) 121168191Sjhb 122168191Sjhb/* Acquire a shared lock. */ 123168191Sjhb#define __sx_slock(sx, file, line) do { \ 124168191Sjhb uintptr_t x = (sx)->sx_lock; \ 125168191Sjhb int contested = 0; \ 126168191Sjhb uint64_t waitstart = 0; \ 127168191Sjhb \ 128168191Sjhb if (!(x & SX_LOCK_SHARED) || \ 129168191Sjhb !atomic_cmpset_acq_ptr(&(sx)->sx_lock, x, \ 130168191Sjhb x + SX_ONE_SHARER)) { \ 131168191Sjhb lock_profile_obtain_lock_failed(&(sx)->lock_object, \ 132168191Sjhb &contested, &waitstart); \ 133168191Sjhb _sx_slock_hard((sx), (file), (line)); \ 134168191Sjhb } \ 135168191Sjhb lock_profile_obtain_lock_success(&(sx)->lock_object, contested, \ 136168191Sjhb waitstart, (file), (line)); \ 137168191Sjhb} while (0) 138168191Sjhb 139168191Sjhb/* 140168191Sjhb * Release a shared lock. We can just drop a single shared lock so 141168191Sjhb * long as we aren't trying to drop the last shared lock when other 142168191Sjhb * threads are waiting for an exclusive lock. This takes advantage of 143168191Sjhb * the fact that an unlocked lock is encoded as a shared lock with a 144168191Sjhb * count of 0. 145168191Sjhb */ 146168191Sjhb#define __sx_sunlock(sx, file, line) do { \ 147168191Sjhb uintptr_t x = (sx)->sx_lock; \ 148168191Sjhb \ 149168191Sjhb if (x == (SX_SHARERS_LOCK(1) | SX_LOCK_EXCLUSIVE_WAITERS) || \ 150168191Sjhb !atomic_cmpset_ptr(&(sx)->sx_lock, x, x - SX_ONE_SHARER)) \ 151168191Sjhb _sx_sunlock_hard((sx), (file), (line)); \ 152168191Sjhb} while (0) 153168191Sjhb 154168191Sjhb/* 155168191Sjhb * Function prototipes. Routines that start with an underscore are not part 156168191Sjhb * of the public interface and are wrappered with a macro. 157168191Sjhb */ 15893672Sarrvoid sx_sysinit(void *arg); 159168191Sjhb#define sx_init(sx, desc) sx_init_flags((sx), (desc), 0) 160168191Sjhbvoid sx_init_flags(struct sx *sx, const char *description, int opts); 16173782Sjasonevoid sx_destroy(struct sx *sx); 16274912Sjhbvoid _sx_slock(struct sx *sx, const char *file, int line); 16374912Sjhbvoid _sx_xlock(struct sx *sx, const char *file, int line); 16478872Sjhbint _sx_try_slock(struct sx *sx, const char *file, int line); 16578872Sjhbint _sx_try_xlock(struct sx *sx, const char *file, int line); 16674912Sjhbvoid _sx_sunlock(struct sx *sx, const char *file, int line); 16774912Sjhbvoid _sx_xunlock(struct sx *sx, const char *file, int line); 16881599Sjasoneint _sx_try_upgrade(struct sx *sx, const char *file, int line); 16981599Sjasonevoid _sx_downgrade(struct sx *sx, const char *file, int line); 170168191Sjhbvoid _sx_xlock_hard(struct sx *sx, uintptr_t tid, const char *file, int 171168191Sjhb line); 172168191Sjhbvoid _sx_slock_hard(struct sx *sx, const char *file, int line); 173168191Sjhbvoid _sx_xunlock_hard(struct sx *sx, uintptr_t tid, const char *file, int 174168191Sjhb line); 175168191Sjhbvoid _sx_sunlock_hard(struct sx *sx, const char *file, int line); 176161721Sjhb#if defined(INVARIANTS) || defined(INVARIANT_SUPPORT) 17785388Sjhbvoid _sx_assert(struct sx *sx, int what, const char *file, int line); 17893688Sarr#endif 179161337Sjhb#ifdef DDB 180161337Sjhbint sx_chain(struct thread *td, struct thread **ownerp); 181161337Sjhb#endif 18293672Sarr 18393672Sarrstruct sx_args { 18493672Sarr struct sx *sa_sx; 18593672Sarr const char *sa_desc; 18693672Sarr}; 18793672Sarr 18893672Sarr#define SX_SYSINIT(name, sxa, desc) \ 18993672Sarr static struct sx_args name##_args = { \ 190149739Sjhb (sxa), \ 191149739Sjhb (desc) \ 19293672Sarr }; \ 19393672Sarr SYSINIT(name##_sx_sysinit, SI_SUB_LOCK, SI_ORDER_MIDDLE, \ 194149739Sjhb sx_sysinit, &name##_args); \ 195149739Sjhb SYSUNINIT(name##_sx_sysuninit, SI_SUB_LOCK, SI_ORDER_MIDDLE, \ 196149739Sjhb sx_destroy, (sxa)) 19773782Sjasone 198168191Sjhb/* 199168191Sjhb * Public interface for lock operations. 200168191Sjhb */ 201168191Sjhb#ifndef LOCK_DEBUG 202168191Sjhb#error "LOCK_DEBUG not defined, include <sys/lock.h> before <sys/sx.h>" 203168191Sjhb#endif 204168191Sjhb#if (LOCK_DEBUG > 0) || defined(SX_NOINLINE) 205168191Sjhb#define sx_xlock(sx) _sx_xlock((sx), LOCK_FILE, LOCK_LINE) 206168191Sjhb#define sx_xunlock(sx) _sx_xunlock((sx), LOCK_FILE, LOCK_LINE) 20783593Sjhb#define sx_slock(sx) _sx_slock((sx), LOCK_FILE, LOCK_LINE) 208168191Sjhb#define sx_sunlock(sx) _sx_sunlock((sx), LOCK_FILE, LOCK_LINE) 209168191Sjhb#else 210168191Sjhb#define sx_xlock(sx) \ 211168191Sjhb __sx_xlock((sx), curthread, LOCK_FILE, LOCK_LINE) 212168191Sjhb#define sx_xunlock(sx) \ 213168191Sjhb __sx_xunlock((sx), curthread, LOCK_FILE, LOCK_LINE) 214168191Sjhb#define sx_slock(sx) __sx_slock((sx), LOCK_FILE, LOCK_LINE) 215168191Sjhb#define sx_sunlock(sx) __sx_sunlock((sx), LOCK_FILE, LOCK_LINE) 216168191Sjhb#endif /* LOCK_DEBUG > 0 || SX_NOINLINE */ 21783593Sjhb#define sx_try_slock(sx) _sx_try_slock((sx), LOCK_FILE, LOCK_LINE) 21883593Sjhb#define sx_try_xlock(sx) _sx_try_xlock((sx), LOCK_FILE, LOCK_LINE) 21983593Sjhb#define sx_try_upgrade(sx) _sx_try_upgrade((sx), LOCK_FILE, LOCK_LINE) 22083593Sjhb#define sx_downgrade(sx) _sx_downgrade((sx), LOCK_FILE, LOCK_LINE) 221168191Sjhb 222168191Sjhb#define sx_xlocked(sx) \ 223168191Sjhb (((sx)->sx_lock & ~(SX_LOCK_FLAGMASK & ~SX_LOCK_SHARED)) == \ 224168191Sjhb (uintptr_t)curthread) 225168191Sjhb 226157296Sjhb#define sx_unlock(sx) do { \ 227159844Sjhb if (sx_xlocked(sx)) \ 228157296Sjhb sx_xunlock(sx); \ 229157296Sjhb else \ 230157296Sjhb sx_sunlock(sx); \ 231157296Sjhb} while (0) 232168191Sjhb 233167387Sjhb#define sx_sleep(chan, sx, pri, wmesg, timo) \ 234167787Sjhb _sleep((chan), &(sx)->lock_object, (pri), (wmesg), (timo)) 23574912Sjhb 236168191Sjhb/* 237168191Sjhb * Options passed to sx_init_flags(). 238168191Sjhb */ 239168191Sjhb#define SX_DUPOK 0x01 240168191Sjhb#define SX_NOPROFILE 0x02 241168191Sjhb#define SX_NOWITNESS 0x04 242168191Sjhb#define SX_QUIET 0x08 243168191Sjhb#define SX_ADAPTIVESPIN 0x10 244168191Sjhb 245168191Sjhb/* 246168191Sjhb * XXX: These options should be renamed as SA_* 247168191Sjhb */ 24885412Sjhb#if defined(INVARIANTS) || defined(INVARIANT_SUPPORT) 24985388Sjhb#define SX_LOCKED LA_LOCKED 25085388Sjhb#define SX_SLOCKED LA_SLOCKED 25185388Sjhb#define SX_XLOCKED LA_XLOCKED 252125419Spjd#define SX_UNLOCKED LA_UNLOCKED 253168191Sjhb#define SX_RECURSED LA_RECURSED 254168191Sjhb#define SX_NOTRECURSED LA_NOTRECURSED 255125444Sbde#endif 25673863Sbmilekic 25785412Sjhb#ifdef INVARIANTS 25885388Sjhb#define sx_assert(sx, what) _sx_assert((sx), (what), LOCK_FILE, LOCK_LINE) 259125444Sbde#else 26085388Sjhb#define sx_assert(sx, what) 261125444Sbde#endif 26273782Sjasone 263125444Sbde#endif /* _KERNEL */ 264125444Sbde 265125444Sbde#endif /* !_SYS_SX_H_ */ 266