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: releng/5.0/sys/sys/mutex.h 100754 2002-07-27 16:54:23Z jhb $
   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_SLEEPABLE   0x00000010      /* We can sleep with this lock. */
   60 #define MTX_DUPOK       0x00000020      /* Don't log a duplicate acquire */
   61 
   62 /*
   63  * Option flags passed to certain lock/unlock routines, through the use
   64  * of corresponding mtx_{lock,unlock}_flags() interface macros.
   65  */
   66 #define MTX_QUIET       LOP_QUIET       /* Don't log a mutex event */
   67 
   68 /*
   69  * State bits kept in mutex->mtx_lock, for the DEFAULT lock type. None of this,
   70  * with the exception of MTX_UNOWNED, applies to spin locks.
   71  */
   72 #define MTX_RECURSED    0x00000001      /* lock recursed (for MTX_DEF only) */
   73 #define MTX_CONTESTED   0x00000002      /* lock contested (for MTX_DEF only) */
   74 #define MTX_UNOWNED     0x00000004      /* Cookie for free mutex */
   75 #define MTX_FLAGMASK    ~(MTX_RECURSED | MTX_CONTESTED)
   76 
   77 #endif  /* _KERNEL */
   78 
   79 #ifndef LOCORE
   80 
   81 /*
   82  * XXX: Friendly reminder to fix things in MP code that is presently being
   83  * XXX: worked on.
   84  */
   85 #define mp_fixme(string)
   86 
   87 #ifdef _KERNEL
   88 
   89 /*
   90  * Prototypes
   91  *
   92  * NOTE: Functions prepended with `_' (underscore) are exported to other parts
   93  *       of the kernel via macros, thus allowing us to use the cpp LOCK_FILE
   94  *       and LOCK_LINE. These functions should not be called directly by any
   95  *       code using the API. Their macros cover their functionality.
   96  *
   97  * [See below for descriptions]
   98  *
   99  */
  100 void    mtx_init(struct mtx *m, const char *name, const char *type, int opts);
  101 void    mtx_destroy(struct mtx *m);
  102 void    mtx_sysinit(void *arg);
  103 void    mutex_init(void);
  104 void    _mtx_lock_sleep(struct mtx *m, int opts, const char *file, int line);
  105 void    _mtx_unlock_sleep(struct mtx *m, int opts, const char *file, int line);
  106 void    _mtx_lock_spin(struct mtx *m, int opts, const char *file, int line);
  107 void    _mtx_unlock_spin(struct mtx *m, int opts, const char *file, int line);
  108 int     _mtx_trylock(struct mtx *m, int opts, const char *file, int line);
  109 void    _mtx_lock_flags(struct mtx *m, int opts, const char *file, int line);
  110 void    _mtx_unlock_flags(struct mtx *m, int opts, const char *file, int line);
  111 void    _mtx_lock_spin_flags(struct mtx *m, int opts, const char *file,
  112                              int line);
  113 void    _mtx_unlock_spin_flags(struct mtx *m, int opts, const char *file,
  114                              int line);
  115 #ifdef INVARIANT_SUPPORT
  116 void    _mtx_assert(struct mtx *m, int what, const char *file, int line);
  117 #endif
  118 int     mtx_lock_giant(int sysctlvar);
  119 void    mtx_unlock_giant(int s);
  120 
  121 /*
  122  * We define our machine-independent (unoptimized) mutex micro-operations
  123  * here, if they are not already defined in the machine-dependent mutex.h 
  124  */
  125 
  126 /* Actually obtain mtx_lock */
  127 #ifndef _obtain_lock
  128 #define _obtain_lock(mp, tid)                                           \
  129         atomic_cmpset_acq_ptr(&(mp)->mtx_lock, (void *)MTX_UNOWNED, (tid))
  130 #endif
  131 
  132 /* Actually release mtx_lock */
  133 #ifndef _release_lock
  134 #define _release_lock(mp, tid)                                          \
  135         atomic_cmpset_rel_ptr(&(mp)->mtx_lock, (tid), (void *)MTX_UNOWNED)
  136 #endif
  137 
  138 /* Actually release mtx_lock quickly, assuming we own it. */
  139 #ifndef _release_lock_quick
  140 #define _release_lock_quick(mp)                                         \
  141         atomic_store_rel_ptr(&(mp)->mtx_lock, (void *)MTX_UNOWNED)
  142 #endif
  143 
  144 /*
  145  * Obtain a sleep lock inline, or call the "hard" function if we can't get it
  146  * easy.
  147  */
  148 #ifndef _get_sleep_lock
  149 #define _get_sleep_lock(mp, tid, opts, file, line) do {                 \
  150         if (!_obtain_lock((mp), (tid)))                                 \
  151                 _mtx_lock_sleep((mp), (opts), (file), (line));          \
  152 } while (0)
  153 #endif
  154 
  155 /*
  156  * Obtain a spin lock inline, or call the "hard" function if we can't get it
  157  * easy. For spinlocks, we handle recursion inline (it turns out that function
  158  * calls can be significantly expensive on some architectures).
  159  * Since spin locks are not _too_ common, inlining this code is not too big 
  160  * a deal.
  161  */
  162 #ifndef _get_spin_lock
  163 #define _get_spin_lock(mp, tid, opts, file, line) do {                  \
  164         critical_enter();                                               \
  165         if (!_obtain_lock((mp), (tid))) {                               \
  166                 if ((mp)->mtx_lock == (uintptr_t)(tid))                 \
  167                         (mp)->mtx_recurse++;                            \
  168                 else                                                    \
  169                         _mtx_lock_spin((mp), (opts), (file), (line));   \
  170         }                                                               \
  171 } while (0)
  172 #endif
  173 
  174 /*
  175  * Release a sleep lock inline, or call the "hard" function if we can't do it
  176  * easy.
  177  */
  178 #ifndef _rel_sleep_lock
  179 #define _rel_sleep_lock(mp, tid, opts, file, line) do {                 \
  180         if (!_release_lock((mp), (tid)))                                \
  181                 _mtx_unlock_sleep((mp), (opts), (file), (line));        \
  182 } while (0)
  183 #endif
  184 
  185 /*
  186  * For spinlocks, we can handle everything inline, as it's pretty simple and
  187  * a function call would be too expensive (at least on some architectures).
  188  * Since spin locks are not _too_ common, inlining this code is not too big 
  189  * a deal.
  190  *
  191  * Since we always perform a critical_enter() when attempting to acquire a
  192  * spin lock, we need to always perform a matching critical_exit() when
  193  * releasing a spin lock.  This includes the recursion cases.
  194  */
  195 #ifndef _rel_spin_lock
  196 #define _rel_spin_lock(mp) do {                                         \
  197         if (mtx_recursed((mp)))                                         \
  198                 (mp)->mtx_recurse--;                                    \
  199         else                                                            \
  200                 _release_lock_quick((mp));                              \
  201         critical_exit();                                        \
  202 } while (0)
  203 #endif
  204 
  205 /*
  206  * Exported lock manipulation interface.
  207  *
  208  * mtx_lock(m) locks MTX_DEF mutex `m'
  209  *
  210  * mtx_lock_spin(m) locks MTX_SPIN mutex `m'
  211  *
  212  * mtx_unlock(m) unlocks MTX_DEF mutex `m'
  213  *
  214  * mtx_unlock_spin(m) unlocks MTX_SPIN mutex `m'
  215  *
  216  * mtx_lock_spin_flags(m, opts) and mtx_lock_flags(m, opts) locks mutex `m'
  217  *     and passes option flags `opts' to the "hard" function, if required.
  218  *     With these routines, it is possible to pass flags such as MTX_QUIET
  219  *     to the appropriate lock manipulation routines.
  220  *
  221  * mtx_trylock(m) attempts to acquire MTX_DEF mutex `m' but doesn't sleep if
  222  *     it cannot. Rather, it returns 0 on failure and non-zero on success.
  223  *     It does NOT handle recursion as we assume that if a caller is properly
  224  *     using this part of the interface, he will know that the lock in question
  225  *     is _not_ recursed.
  226  *
  227  * mtx_trylock_flags(m, opts) is used the same way as mtx_trylock() but accepts
  228  *     relevant option flags `opts.'
  229  *
  230  * mtx_initialized(m) returns non-zero if the lock `m' has been initialized.
  231  *
  232  * mtx_owned(m) returns non-zero if the current thread owns the lock `m'
  233  *
  234  * mtx_recursed(m) returns non-zero if the lock `m' is presently recursed.
  235  */ 
  236 #define mtx_lock(m)             mtx_lock_flags((m), 0)
  237 #define mtx_lock_spin(m)        mtx_lock_spin_flags((m), 0)
  238 #define mtx_trylock(m)          mtx_trylock_flags((m), 0)
  239 #define mtx_unlock(m)           mtx_unlock_flags((m), 0)
  240 #define mtx_unlock_spin(m)      mtx_unlock_spin_flags((m), 0)
  241 
  242 struct mtx *mtx_pool_find(void *ptr);
  243 struct mtx *mtx_pool_alloc(void);
  244 void mtx_pool_lock(void *ptr);
  245 void mtx_pool_unlock(void *ptr);
  246 
  247 extern int mtx_pool_valid;
  248 
  249 #ifndef LOCK_DEBUG
  250 #error LOCK_DEBUG not defined, include <sys/lock.h> before <sys/mutex.h>
  251 #endif
  252 #if LOCK_DEBUG > 0
  253 #define mtx_lock_flags(m, opts)                                         \
  254         _mtx_lock_flags((m), (opts), LOCK_FILE, LOCK_LINE)
  255 #define mtx_unlock_flags(m, opts)                                       \
  256         _mtx_unlock_flags((m), (opts), LOCK_FILE, LOCK_LINE)
  257 #define mtx_lock_spin_flags(m, opts)                                    \
  258         _mtx_lock_spin_flags((m), (opts), LOCK_FILE, LOCK_LINE)
  259 #define mtx_unlock_spin_flags(m, opts)                                  \
  260         _mtx_unlock_spin_flags((m), (opts), LOCK_FILE, LOCK_LINE)
  261 #else   /* LOCK_DEBUG == 0 */
  262 #define mtx_lock_flags(m, opts)                                         \
  263         _get_sleep_lock((m), curthread, (opts), LOCK_FILE, LOCK_LINE)
  264 #define mtx_unlock_flags(m, opts)                                       \
  265         _rel_sleep_lock((m), curthread, (opts), LOCK_FILE, LOCK_LINE)
  266 #ifndef SMPnotyet
  267 #define mtx_lock_spin_flags(m, opts)                                    \
  268         _get_spin_lock((m), curthread, (opts), LOCK_FILE, LOCK_LINE)
  269 #define mtx_unlock_spin_flags(m, opts)                                  \
  270         _rel_spin_lock((m))
  271 #else   /* SMP */
  272 #define mtx_lock_spin_flags(m, opts)    critical_enter()
  273 #define mtx_unlock_spin_flags(m, opts)  critical_exit()
  274 #endif  /* SMP */
  275 #endif  /* LOCK_DEBUG */
  276 
  277 #define mtx_trylock_flags(m, opts)                                      \
  278         _mtx_trylock((m), (opts), LOCK_FILE, LOCK_LINE)
  279 
  280 #define mtx_initialized(m)      ((m)->mtx_object.lo_flags & LO_INITIALIZED)
  281 
  282 #define mtx_owned(m)    (((m)->mtx_lock & MTX_FLAGMASK) == (uintptr_t)curthread)
  283 
  284 #define mtx_recursed(m) ((m)->mtx_recurse != 0)
  285 
  286 #define mtx_name(m)     ((m)->mtx_object.lo_name)
  287 
  288 /*
  289  * Global locks.
  290  */
  291 extern struct mtx sched_lock;
  292 extern struct mtx Giant;
  293 
  294 /*
  295  * Giant lock sysctl variables used by other modules
  296  */
  297 extern int kern_giant_proc;
  298 extern int kern_giant_file;
  299 extern int kern_giant_ucred;
  300 
  301 /*
  302  * Giant lock manipulation and clean exit macros.
  303  * Used to replace return with an exit Giant and return.
  304  *
  305  * Note that DROP_GIANT*() needs to be paired with PICKUP_GIANT() 
  306  */
  307 #define DROP_GIANT()                                                    \
  308 do {                                                                    \
  309         int _giantcnt;                                                  \
  310         WITNESS_SAVE_DECL(Giant);                                       \
  311                                                                         \
  312         if (mtx_owned(&Giant))                                          \
  313                 WITNESS_SAVE(&Giant.mtx_object, Giant);                 \
  314         for (_giantcnt = 0; mtx_owned(&Giant); _giantcnt++)             \
  315                 mtx_unlock(&Giant)
  316 
  317 #define PICKUP_GIANT()                                                  \
  318         mtx_assert(&Giant, MA_NOTOWNED);                                \
  319         while (_giantcnt--)                                             \
  320                 mtx_lock(&Giant);                                       \
  321         if (mtx_owned(&Giant))                                          \
  322                 WITNESS_RESTORE(&Giant.mtx_object, Giant);              \
  323 } while (0)
  324 
  325 #define PARTIAL_PICKUP_GIANT()                                          \
  326         mtx_assert(&Giant, MA_NOTOWNED);                                \
  327         while (_giantcnt--)                                             \
  328                 mtx_lock(&Giant);                                       \
  329         if (mtx_owned(&Giant))                                          \
  330                 WITNESS_RESTORE(&Giant.mtx_object, Giant)
  331 
  332 #define UGAR(rval) do {                                                 \
  333         int _val = (rval);                                              \
  334         mtx_unlock(&Giant);                                             \
  335         return (_val);                                                  \
  336 } while (0)
  337 
  338 struct mtx_args {
  339         struct mtx      *ma_mtx;
  340         const char      *ma_desc;
  341         int              ma_opts;
  342 };
  343 
  344 #define MTX_SYSINIT(name, mtx, desc, opts)                              \
  345         static struct mtx_args name##_args = {                          \
  346                 mtx,                                                    \
  347                 desc,                                                   \
  348                 opts                                                    \
  349         };                                                              \
  350         SYSINIT(name##_mtx_sysinit, SI_SUB_LOCK, SI_ORDER_MIDDLE,       \
  351             mtx_sysinit, &name##_args)
  352 
  353 /*
  354  * The INVARIANTS-enabled mtx_assert() functionality.
  355  *
  356  * The constants need to be defined for INVARIANT_SUPPORT infrastructure
  357  * support as _mtx_assert() itself uses them and the latter implies that
  358  * _mtx_assert() must build.
  359  */
  360 #ifdef INVARIANT_SUPPORT
  361 #define MA_OWNED        0x01
  362 #define MA_NOTOWNED     0x02
  363 #define MA_RECURSED     0x04
  364 #define MA_NOTRECURSED  0x08
  365 #endif /* INVARIANT_SUPPORT */
  366 
  367 #ifdef INVARIANTS
  368 #define mtx_assert(m, what)                                             \
  369         _mtx_assert((m), (what), __FILE__, __LINE__)
  370 
  371 #define GIANT_REQUIRED  mtx_assert(&Giant, MA_OWNED)
  372 
  373 #else   /* INVARIANTS */
  374 #define mtx_assert(m, what)
  375 #define GIANT_REQUIRED
  376 #endif  /* INVARIANTS */
  377 
  378 /*
  379  * Common lock type names.
  380  */
  381 #define MTX_NETWORK_LOCK        "network driver"
  382 
  383 #endif  /* _KERNEL */
  384 #endif  /* !LOCORE */
  385 #endif  /* _SYS_MUTEX_H_ */

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