The Design and Implementation of the FreeBSD Operating System, Second Edition
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FreeBSD/Linux Kernel Cross Reference
sys/sys/mutex.h

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    1 /*-
    2  * Copyright (c) 1997 Berkeley Software Design, Inc. All rights reserved.
    3  *
    4  * Redistribution and use in source and binary forms, with or without
    5  * modification, are permitted provided that the following conditions
    6  * are met:
    7  * 1. Redistributions of source code must retain the above copyright
    8  *    notice, this list of conditions and the following disclaimer.
    9  * 2. Redistributions in binary form must reproduce the above copyright
   10  *    notice, this list of conditions and the following disclaimer in the
   11  *    documentation and/or other materials provided with the distribution.
   12  * 3. Berkeley Software Design Inc's name may not be used to endorse or
   13  *    promote products derived from this software without specific prior
   14  *    written permission.
   15  *
   16  * THIS SOFTWARE IS PROVIDED BY BERKELEY SOFTWARE DESIGN INC ``AS IS'' AND
   17  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   18  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   19  * ARE DISCLAIMED.  IN NO EVENT SHALL BERKELEY SOFTWARE DESIGN INC BE LIABLE
   20  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   21  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   22  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   23  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   24  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   25  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   26  * SUCH DAMAGE.
   27  *
   28  *      from BSDI $Id: mutex.h,v 2.7.2.35 2000/04/27 03:10:26 cp Exp $
   29  * $FreeBSD: src/sys/sys/mutex.h,v 1.73.2.3 2005/03/28 20:17:30 jhb Exp $
   30  */
   31 
   32 #ifndef _SYS_MUTEX_H_
   33 #define _SYS_MUTEX_H_
   34 
   35 #ifndef LOCORE
   36 #include <sys/queue.h>
   37 #include <sys/_lock.h>
   38 #include <sys/_mutex.h>
   39 
   40 #ifdef _KERNEL
   41 #include <sys/pcpu.h>
   42 #include <machine/atomic.h>
   43 #include <machine/cpufunc.h>
   44 #endif  /* _KERNEL_ */
   45 #endif  /* !LOCORE */
   46 
   47 #include <machine/mutex.h>
   48 
   49 #ifdef _KERNEL
   50 
   51 /*
   52  * Mutex types and options passed to mtx_init().  MTX_QUIET can also be
   53  * passed in.
   54  */
   55 #define MTX_DEF         0x00000000      /* DEFAULT (sleep) lock */ 
   56 #define MTX_SPIN        0x00000001      /* Spin lock (disables interrupts) */
   57 #define MTX_RECURSE     0x00000004      /* Option: lock allowed to recurse */
   58 #define MTX_NOWITNESS   0x00000008      /* Don't do any witness checking. */
   59 #define MTX_DUPOK       0x00000020      /* Don't log a duplicate acquire */
   60 
   61 /*
   62  * Option flags passed to certain lock/unlock routines, through the use
   63  * of corresponding mtx_{lock,unlock}_flags() interface macros.
   64  */
   65 #define MTX_QUIET       LOP_QUIET       /* Don't log a mutex event */
   66 
   67 /*
   68  * State bits kept in mutex->mtx_lock, for the DEFAULT lock type. None of this,
   69  * with the exception of MTX_UNOWNED, applies to spin locks.
   70  */
   71 #define MTX_RECURSED    0x00000001      /* lock recursed (for MTX_DEF only) */
   72 #define MTX_CONTESTED   0x00000002      /* lock contested (for MTX_DEF only) */
   73 #define MTX_UNOWNED     0x00000004      /* Cookie for free mutex */
   74 #define MTX_FLAGMASK    ~(MTX_RECURSED | MTX_CONTESTED)
   75 
   76 #endif  /* _KERNEL */
   77 
   78 #ifndef LOCORE
   79 
   80 /*
   81  * XXX: Friendly reminder to fix things in MP code that is presently being
   82  * XXX: worked on.
   83  */
   84 #define mp_fixme(string)
   85 
   86 #ifdef _KERNEL
   87 
   88 /*
   89  * Prototypes
   90  *
   91  * NOTE: Functions prepended with `_' (underscore) are exported to other parts
   92  *       of the kernel via macros, thus allowing us to use the cpp LOCK_FILE
   93  *       and LOCK_LINE. These functions should not be called directly by any
   94  *       code using the API. Their macros cover their functionality.
   95  *
   96  * [See below for descriptions]
   97  *
   98  */
   99 void    mtx_init(struct mtx *m, const char *name, const char *type, int opts);
  100 void    mtx_destroy(struct mtx *m);
  101 void    mtx_sysinit(void *arg);
  102 void    mutex_init(void);
  103 void    _mtx_lock_sleep(struct mtx *m, struct thread *td, int opts,
  104             const char *file, int line);
  105 void    _mtx_unlock_sleep(struct mtx *m, int opts, const char *file, int line);
  106 #ifdef SMP
  107 void    _mtx_lock_spin(struct mtx *m, struct thread *td, int opts,
  108             const char *file, int line);
  109 #endif
  110 void    _mtx_unlock_spin(struct mtx *m, int opts, const char *file, int line);
  111 int     _mtx_trylock(struct mtx *m, int opts, const char *file, int line);
  112 void    _mtx_lock_flags(struct mtx *m, int opts, const char *file, int line);
  113 void    _mtx_unlock_flags(struct mtx *m, int opts, const char *file, int line);
  114 void    _mtx_lock_spin_flags(struct mtx *m, int opts, const char *file,
  115              int line);
  116 void    _mtx_unlock_spin_flags(struct mtx *m, int opts, const char *file,
  117              int line);
  118 #if defined(INVARIANTS) || defined(INVARIANT_SUPPORT)
  119 void    _mtx_assert(struct mtx *m, int what, const char *file, int line);
  120 #endif
  121 
  122 /*
  123  * We define our machine-independent (unoptimized) mutex micro-operations
  124  * here, if they are not already defined in the machine-dependent mutex.h 
  125  */
  126 
  127 /* Actually obtain mtx_lock */
  128 #ifndef _obtain_lock
  129 #define _obtain_lock(mp, tid)                                           \
  130         atomic_cmpset_acq_ptr(&(mp)->mtx_lock, (void *)MTX_UNOWNED, (tid))
  131 #endif
  132 
  133 /* Actually release mtx_lock */
  134 #ifndef _release_lock
  135 #define _release_lock(mp, tid)                                          \
  136         atomic_cmpset_rel_ptr(&(mp)->mtx_lock, (tid), (void *)MTX_UNOWNED)
  137 #endif
  138 
  139 /* Actually release mtx_lock quickly, assuming we own it. */
  140 #ifndef _release_lock_quick
  141 #define _release_lock_quick(mp)                                         \
  142         atomic_store_rel_ptr(&(mp)->mtx_lock, (void *)MTX_UNOWNED)
  143 #endif
  144 
  145 /*
  146  * Obtain a sleep lock inline, or call the "hard" function if we can't get it
  147  * easy.
  148  */
  149 #ifndef _get_sleep_lock
  150 #define _get_sleep_lock(mp, tid, opts, file, line) do {                 \
  151         struct thread *_tid = (tid);                                    \
  152                                                                         \
  153         if (!_obtain_lock((mp), _tid))                                  \
  154                 _mtx_lock_sleep((mp), _tid, (opts), (file), (line));    \
  155 } while (0)
  156 #endif
  157 
  158 /*
  159  * Obtain a spin lock inline, or call the "hard" function if we can't get it
  160  * easy. For spinlocks, we handle recursion inline (it turns out that function
  161  * calls can be significantly expensive on some architectures).
  162  * Since spin locks are not _too_ common, inlining this code is not too big 
  163  * a deal.
  164  */
  165 #ifndef _get_spin_lock
  166 #ifdef SMP
  167 #define _get_spin_lock(mp, tid, opts, file, line) do {                  \
  168         struct thread *_tid = (tid);                                    \
  169                                                                         \
  170         critical_enter();                                               \
  171         if (!_obtain_lock((mp), _tid)) {                                \
  172                 if ((mp)->mtx_lock == (uintptr_t)_tid)                  \
  173                         (mp)->mtx_recurse++;                            \
  174                 else                                                    \
  175                         _mtx_lock_spin((mp), _tid, (opts), (file), (line)); \
  176         }                                                               \
  177 } while (0)
  178 #else /* SMP */
  179 #define _get_spin_lock(mp, tid, opts, file, line) do {                  \
  180         struct thread *_tid = (tid);                                    \
  181                                                                         \
  182         critical_enter();                                               \
  183         if ((mp)->mtx_lock == (uintptr_t)_tid)                          \
  184                 (mp)->mtx_recurse++;                                    \
  185         else {                                                          \
  186                 KASSERT((mp)->mtx_lock == MTX_UNOWNED, ("corrupt spinlock")); \
  187                 (mp)->mtx_lock = (uintptr_t)_tid;                       \
  188         }                                                               \
  189 } while (0)
  190 #endif /* SMP */
  191 #endif
  192 
  193 /*
  194  * Release a sleep lock inline, or call the "hard" function if we can't do it
  195  * easy.
  196  */
  197 #ifndef _rel_sleep_lock
  198 #define _rel_sleep_lock(mp, tid, opts, file, line) do {                 \
  199         if (!_release_lock((mp), (tid)))                                \
  200                 _mtx_unlock_sleep((mp), (opts), (file), (line));        \
  201 } while (0)
  202 #endif
  203 
  204 /*
  205  * For spinlocks, we can handle everything inline, as it's pretty simple and
  206  * a function call would be too expensive (at least on some architectures).
  207  * Since spin locks are not _too_ common, inlining this code is not too big 
  208  * a deal.
  209  *
  210  * Since we always perform a critical_enter() when attempting to acquire a
  211  * spin lock, we need to always perform a matching critical_exit() when
  212  * releasing a spin lock.  This includes the recursion cases.
  213  */
  214 #ifndef _rel_spin_lock
  215 #ifdef SMP
  216 #define _rel_spin_lock(mp) do {                                         \
  217         if (mtx_recursed((mp)))                                         \
  218                 (mp)->mtx_recurse--;                                    \
  219         else                                                            \
  220                 _release_lock_quick((mp));                              \
  221         critical_exit();                                                \
  222 } while (0)
  223 #else /* SMP */
  224 #define _rel_spin_lock(mp) do {                                         \
  225         if (mtx_recursed((mp)))                                         \
  226                 (mp)->mtx_recurse--;                                    \
  227         else                                                            \
  228                 (mp)->mtx_lock = MTX_UNOWNED;                           \
  229         critical_exit();                                                \
  230 } while (0)
  231 #endif /* SMP */
  232 #endif
  233 
  234 /*
  235  * Exported lock manipulation interface.
  236  *
  237  * mtx_lock(m) locks MTX_DEF mutex `m'
  238  *
  239  * mtx_lock_spin(m) locks MTX_SPIN mutex `m'
  240  *
  241  * mtx_unlock(m) unlocks MTX_DEF mutex `m'
  242  *
  243  * mtx_unlock_spin(m) unlocks MTX_SPIN mutex `m'
  244  *
  245  * mtx_lock_spin_flags(m, opts) and mtx_lock_flags(m, opts) locks mutex `m'
  246  *     and passes option flags `opts' to the "hard" function, if required.
  247  *     With these routines, it is possible to pass flags such as MTX_QUIET
  248  *     to the appropriate lock manipulation routines.
  249  *
  250  * mtx_trylock(m) attempts to acquire MTX_DEF mutex `m' but doesn't sleep if
  251  *     it cannot. Rather, it returns 0 on failure and non-zero on success.
  252  *     It does NOT handle recursion as we assume that if a caller is properly
  253  *     using this part of the interface, he will know that the lock in question
  254  *     is _not_ recursed.
  255  *
  256  * mtx_trylock_flags(m, opts) is used the same way as mtx_trylock() but accepts
  257  *     relevant option flags `opts.'
  258  *
  259  * mtx_initialized(m) returns non-zero if the lock `m' has been initialized.
  260  *
  261  * mtx_owned(m) returns non-zero if the current thread owns the lock `m'
  262  *
  263  * mtx_recursed(m) returns non-zero if the lock `m' is presently recursed.
  264  */ 
  265 #define mtx_lock(m)             mtx_lock_flags((m), 0)
  266 #define mtx_lock_spin(m)        mtx_lock_spin_flags((m), 0)
  267 #define mtx_trylock(m)          mtx_trylock_flags((m), 0)
  268 #define mtx_unlock(m)           mtx_unlock_flags((m), 0)
  269 #define mtx_unlock_spin(m)      mtx_unlock_spin_flags((m), 0)
  270 
  271 struct mtx_pool;
  272 
  273 struct mtx_pool *mtx_pool_create(const char *mtx_name, int pool_size, int opts);
  274 void mtx_pool_destroy(struct mtx_pool **poolp);
  275 struct mtx *mtx_pool_find(struct mtx_pool *pool, void *ptr);
  276 struct mtx *mtx_pool_alloc(struct mtx_pool *pool);
  277 #define mtx_pool_lock(pool, ptr)                                        \
  278         mtx_lock(mtx_pool_find((pool), (ptr)))
  279 #define mtx_pool_lock_spin(pool, ptr)                                   \
  280         mtx_lock_spin(mtx_pool_find((pool), (ptr)))
  281 #define mtx_pool_unlock(pool, ptr)                                      \
  282         mtx_unlock(mtx_pool_find((pool), (ptr)))
  283 #define mtx_pool_unlock_spin(pool, ptr)                                 \
  284         mtx_unlock_spin(mtx_pool_find((pool), (ptr)))
  285 
  286 /*
  287  * mtxpool_lockbuilder is a pool of sleep locks that is not witness
  288  * checked and should only be used for building higher level locks.
  289  *
  290  * mtxpool_sleep is a general purpose pool of sleep mutexes.
  291  */
  292 extern struct mtx_pool *mtxpool_lockbuilder;
  293 extern struct mtx_pool *mtxpool_sleep;
  294 
  295 #ifndef LOCK_DEBUG
  296 #error LOCK_DEBUG not defined, include <sys/lock.h> before <sys/mutex.h>
  297 #endif
  298 #if LOCK_DEBUG > 0 || defined(MUTEX_NOINLINE)
  299 #define mtx_lock_flags(m, opts)                                         \
  300         _mtx_lock_flags((m), (opts), LOCK_FILE, LOCK_LINE)
  301 #define mtx_unlock_flags(m, opts)                                       \
  302         _mtx_unlock_flags((m), (opts), LOCK_FILE, LOCK_LINE)
  303 #define mtx_lock_spin_flags(m, opts)                                    \
  304         _mtx_lock_spin_flags((m), (opts), LOCK_FILE, LOCK_LINE)
  305 #define mtx_unlock_spin_flags(m, opts)                                  \
  306         _mtx_unlock_spin_flags((m), (opts), LOCK_FILE, LOCK_LINE)
  307 #else   /* LOCK_DEBUG == 0 && !MUTEX_NOINLINE */
  308 #define mtx_lock_flags(m, opts)                                         \
  309         _get_sleep_lock((m), curthread, (opts), LOCK_FILE, LOCK_LINE)
  310 #define mtx_unlock_flags(m, opts)                                       \
  311         _rel_sleep_lock((m), curthread, (opts), LOCK_FILE, LOCK_LINE)
  312 #define mtx_lock_spin_flags(m, opts)                                    \
  313         _get_spin_lock((m), curthread, (opts), LOCK_FILE, LOCK_LINE)
  314 #define mtx_unlock_spin_flags(m, opts)                                  \
  315         _rel_spin_lock((m))
  316 #endif  /* LOCK_DEBUG > 0 || MUTEX_NOINLINE */
  317 
  318 #define mtx_trylock_flags(m, opts)                                      \
  319         _mtx_trylock((m), (opts), LOCK_FILE, LOCK_LINE)
  320 
  321 #define mtx_initialized(m)      ((m)->mtx_object.lo_flags & LO_INITIALIZED)
  322 
  323 #define mtx_owned(m)    (((m)->mtx_lock & MTX_FLAGMASK) == (uintptr_t)curthread)
  324 
  325 #define mtx_recursed(m) ((m)->mtx_recurse != 0)
  326 
  327 #define mtx_name(m)     ((m)->mtx_object.lo_name)
  328 
  329 /*
  330  * Global locks.
  331  */
  332 extern struct mtx sched_lock;
  333 extern struct mtx Giant;
  334 
  335 /*
  336  * Giant lock manipulation and clean exit macros.
  337  * Used to replace return with an exit Giant and return.
  338  *
  339  * Note that DROP_GIANT*() needs to be paired with PICKUP_GIANT() 
  340  * The #ifndef is to allow lint-like tools to redefine DROP_GIANT.
  341  */
  342 #ifndef DROP_GIANT
  343 #define DROP_GIANT()                                                    \
  344 do {                                                                    \
  345         int _giantcnt;                                                  \
  346         WITNESS_SAVE_DECL(Giant);                                       \
  347                                                                         \
  348         if (mtx_owned(&Giant))                                          \
  349                 WITNESS_SAVE(&Giant.mtx_object, Giant);                 \
  350         for (_giantcnt = 0; mtx_owned(&Giant); _giantcnt++)             \
  351                 mtx_unlock(&Giant)
  352 
  353 #define PICKUP_GIANT()                                                  \
  354         mtx_assert(&Giant, MA_NOTOWNED);                                \
  355         while (_giantcnt--)                                             \
  356                 mtx_lock(&Giant);                                       \
  357         if (mtx_owned(&Giant))                                          \
  358                 WITNESS_RESTORE(&Giant.mtx_object, Giant);              \
  359 } while (0)
  360 
  361 #define PARTIAL_PICKUP_GIANT()                                          \
  362         mtx_assert(&Giant, MA_NOTOWNED);                                \
  363         while (_giantcnt--)                                             \
  364                 mtx_lock(&Giant);                                       \
  365         if (mtx_owned(&Giant))                                          \
  366                 WITNESS_RESTORE(&Giant.mtx_object, Giant)
  367 #endif
  368 
  369 /*
  370  * Network MPSAFE temporary workarounds.  When debug_mpsafenet
  371  * is 1 the network is assumed to operate without Giant on the
  372  * input path and protocols that require Giant must collect it
  373  * on entry.  When 0 Giant is grabbed in the network interface
  374  * ISR's and in the netisr path and there is no need to grab
  375  * the Giant lock.  Note that, unlike GIANT_PICKUP() and
  376  * GIANT_DROP(), these macros directly wrap mutex operations
  377  * without special recursion handling.
  378  *
  379  * This mechanism is intended as temporary until everything of
  380  * importance is properly locked.  Note: the semantics for
  381  * NET_{LOCK,UNLOCK}_GIANT() are not the same as DROP_GIANT()
  382  * and PICKUP_GIANT(), as they are plain mutex operations
  383  * without a recursion counter.
  384  */
  385 extern  int debug_mpsafenet;            /* defined in net/netisr.c */
  386 #define NET_LOCK_GIANT() do {                                           \
  387         if (!debug_mpsafenet)                                           \
  388                 mtx_lock(&Giant);                                       \
  389 } while (0)
  390 #define NET_UNLOCK_GIANT() do {                                         \
  391         if (!debug_mpsafenet)                                           \
  392                 mtx_unlock(&Giant);                                     \
  393 } while (0)
  394 #define NET_ASSERT_GIANT() do {                                         \
  395         if (!debug_mpsafenet)                                           \
  396                 mtx_assert(&Giant, MA_OWNED);                           \
  397 } while (0)
  398 #define NET_CALLOUT_MPSAFE      (debug_mpsafenet ? CALLOUT_MPSAFE : 0)
  399 
  400 #define UGAR(rval) do {                                                 \
  401         int _val = (rval);                                              \
  402         mtx_unlock(&Giant);                                             \
  403         return (_val);                                                  \
  404 } while (0)
  405 
  406 struct mtx_args {
  407         struct mtx      *ma_mtx;
  408         const char      *ma_desc;
  409         int              ma_opts;
  410 };
  411 
  412 #define MTX_SYSINIT(name, mtx, desc, opts)                              \
  413         static struct mtx_args name##_args = {                          \
  414                 (mtx),                                                  \
  415                 (desc),                                                 \
  416                 (opts)                                                  \
  417         };                                                              \
  418         SYSINIT(name##_mtx_sysinit, SI_SUB_LOCK, SI_ORDER_MIDDLE,       \
  419             mtx_sysinit, &name##_args)
  420 
  421 /*
  422  * The INVARIANTS-enabled mtx_assert() functionality.
  423  *
  424  * The constants need to be defined for INVARIANT_SUPPORT infrastructure
  425  * support as _mtx_assert() itself uses them and the latter implies that
  426  * _mtx_assert() must build.
  427  */
  428 #if defined(INVARIANTS) || defined(INVARIANT_SUPPORT)
  429 #define MA_OWNED        0x01
  430 #define MA_NOTOWNED     0x02
  431 #define MA_RECURSED     0x04
  432 #define MA_NOTRECURSED  0x08
  433 #endif
  434 
  435 #ifdef INVARIANTS
  436 #define mtx_assert(m, what)                                             \
  437         _mtx_assert((m), (what), __FILE__, __LINE__)
  438 
  439 #define GIANT_REQUIRED  mtx_assert(&Giant, MA_OWNED)
  440 
  441 #else   /* INVARIANTS */
  442 #define mtx_assert(m, what)
  443 #define GIANT_REQUIRED
  444 #endif  /* INVARIANTS */
  445 
  446 /*
  447  * Common lock type names.
  448  */
  449 #define MTX_NETWORK_LOCK        "network driver"
  450 
  451 #endif  /* _KERNEL */
  452 #endif  /* !LOCORE */
  453 #endif  /* _SYS_MUTEX_H_ */

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