The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)


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FreeBSD/Linux Kernel Cross Reference
sys/sys/sx.h

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    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: stable/12/sys/sys/sx.h 336230 2018-07-12 22:34:40Z mjg $
   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  */
  104 void    sx_sysinit(void *arg);
  105 #define sx_init(sx, desc)       sx_init_flags((sx), (desc), 0)
  106 void    sx_init_flags(struct sx *sx, const char *description, int opts);
  107 void    sx_destroy(struct sx *sx);
  108 int     sx_try_slock_int(struct sx *sx LOCK_FILE_LINE_ARG_DEF);
  109 int     sx_try_slock_(struct sx *sx, const char *file, int line);
  110 int     sx_try_xlock_int(struct sx *sx LOCK_FILE_LINE_ARG_DEF);
  111 int     sx_try_xlock_(struct sx *sx, const char *file, int line);
  112 int     sx_try_upgrade_int(struct sx *sx LOCK_FILE_LINE_ARG_DEF);
  113 int     sx_try_upgrade_(struct sx *sx, const char *file, int line);
  114 void    sx_downgrade_int(struct sx *sx LOCK_FILE_LINE_ARG_DEF);
  115 void    sx_downgrade_(struct sx *sx, const char *file, int line);
  116 int     _sx_slock_int(struct sx *sx, int opts LOCK_FILE_LINE_ARG_DEF);
  117 int     _sx_slock(struct sx *sx, int opts, const char *file, int line);
  118 int     _sx_xlock(struct sx *sx, int opts, const char *file, int line);
  119 void    _sx_sunlock_int(struct sx *sx LOCK_FILE_LINE_ARG_DEF);
  120 void    _sx_sunlock(struct sx *sx, const char *file, int line);
  121 void    _sx_xunlock(struct sx *sx, const char *file, int line);
  122 int     _sx_xlock_hard(struct sx *sx, uintptr_t x, int opts LOCK_FILE_LINE_ARG_DEF);
  123 void    _sx_xunlock_hard(struct sx *sx, uintptr_t x LOCK_FILE_LINE_ARG_DEF);
  124 #if defined(INVARIANTS) || defined(INVARIANT_SUPPORT)
  125 void    _sx_assert(const struct sx *sx, int what, const char *file, int line);
  126 #endif
  127 #ifdef DDB
  128 int     sx_chain(struct thread *td, struct thread **ownerp);
  129 #endif
  130 
  131 struct 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. */
  158 static __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. */
  174 static __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_NOADAPTIVE           0x10
  277 #define SX_RECURSE              0x20
  278 #define SX_NEW                  0x40
  279 
  280 /*
  281  * Options passed to sx_*lock_hard().
  282  */
  283 #define SX_INTERRUPTIBLE        0x40
  284 
  285 #if defined(INVARIANTS) || defined(INVARIANT_SUPPORT)
  286 #define SA_LOCKED               LA_LOCKED
  287 #define SA_SLOCKED              LA_SLOCKED
  288 #define SA_XLOCKED              LA_XLOCKED
  289 #define SA_UNLOCKED             LA_UNLOCKED
  290 #define SA_RECURSED             LA_RECURSED
  291 #define SA_NOTRECURSED          LA_NOTRECURSED
  292 
  293 /* Backwards compatibility. */
  294 #define SX_LOCKED               LA_LOCKED
  295 #define SX_SLOCKED              LA_SLOCKED
  296 #define SX_XLOCKED              LA_XLOCKED
  297 #define SX_UNLOCKED             LA_UNLOCKED
  298 #define SX_RECURSED             LA_RECURSED
  299 #define SX_NOTRECURSED          LA_NOTRECURSED
  300 #endif
  301 
  302 #endif /* _KERNEL */
  303 
  304 #endif /* !_SYS_SX_H_ */

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