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219 lines
6.8 KiB
C
219 lines
6.8 KiB
C
/*-
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* Copyright (c) 2001 Matthew Dillon. All Rights Reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL AUTHOR OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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/* Mutex pool routines. These routines are designed to be used as short
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* term leaf mutexes (e.g. the last mutex you might aquire other then
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* calling msleep()). They operate using a shared pool. A mutex is chosen
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* from the pool based on the supplied pointer (which may or may not be
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* valid).
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*
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* Advantages:
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* - no structural overhead. Mutexes can be associated with structures
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* without adding bloat to the structures.
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* - mutexes can be obtained for invalid pointers, useful when uses
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* mutexes to interlock destructor ops.
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* - no initialization/destructor overhead.
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* - can be used with msleep.
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*
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* Disadvantages:
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* - should generally only be used as leaf mutexes.
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* - pool/pool dependancy ordering cannot be depended on.
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* - possible L1 cache mastersip contention between cpus.
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*/
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#include <sys/cdefs.h>
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__FBSDID("$FreeBSD$");
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#include <sys/param.h>
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#include <sys/proc.h>
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#include <sys/kernel.h>
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#include <sys/ktr.h>
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#include <sys/lock.h>
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#include <sys/malloc.h>
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#include <sys/mutex.h>
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#include <sys/systm.h>
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static MALLOC_DEFINE(M_MTXPOOL, "mtx_pool", "mutex pool");
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/* Pool sizes must be a power of two */
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#ifndef MTX_POOL_LOCKBUILDER_SIZE
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#define MTX_POOL_LOCKBUILDER_SIZE 128
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#endif
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#ifndef MTX_POOL_SLEEP_SIZE
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#define MTX_POOL_SLEEP_SIZE 128
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#endif
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struct mtxpool_header {
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int mtxpool_size;
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int mtxpool_mask;
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int mtxpool_shift;
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int mtxpool_next;
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};
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struct mtx_pool {
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struct mtxpool_header mtx_pool_header;
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struct mtx mtx_pool_ary[1];
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};
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static struct mtx_pool_lockbuilder {
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struct mtxpool_header mtx_pool_header;
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struct mtx mtx_pool_ary[MTX_POOL_LOCKBUILDER_SIZE];
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} lockbuilder_pool;
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#define mtx_pool_size mtx_pool_header.mtxpool_size
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#define mtx_pool_mask mtx_pool_header.mtxpool_mask
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#define mtx_pool_shift mtx_pool_header.mtxpool_shift
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#define mtx_pool_next mtx_pool_header.mtxpool_next
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struct mtx_pool *mtxpool_sleep;
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struct mtx_pool *mtxpool_lockbuilder;
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#if UINTPTR_MAX == UINT64_MAX /* 64 bits */
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# define POINTER_BITS 64
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# define HASH_MULTIPLIER 11400714819323198485u /* (2^64)*(sqrt(5)-1)/2 */
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#else /* assume 32 bits */
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# define POINTER_BITS 32
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# define HASH_MULTIPLIER 2654435769u /* (2^32)*(sqrt(5)-1)/2 */
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#endif
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/*
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* Return the (shared) pool mutex associated with the specified address.
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* The returned mutex is a leaf level mutex, meaning that if you obtain it
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* you cannot obtain any other mutexes until you release it. You can
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* legally msleep() on the mutex.
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*/
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struct mtx *
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mtx_pool_find(struct mtx_pool *pool, void *ptr)
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{
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int p;
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KASSERT(pool != NULL, ("_mtx_pool_find(): null pool"));
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/*
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* Fibonacci hash, see Knuth's
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* _Art of Computer Programming, Volume 3 / Sorting and Searching_
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*/
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p = ((HASH_MULTIPLIER * (uintptr_t)ptr) >> pool->mtx_pool_shift) &
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pool->mtx_pool_mask;
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return (&pool->mtx_pool_ary[p]);
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}
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static void
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mtx_pool_initialize(struct mtx_pool *pool, const char *mtx_name, int pool_size,
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int opts)
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{
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int i, maskbits;
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pool->mtx_pool_size = pool_size;
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pool->mtx_pool_mask = pool_size - 1;
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for (i = 1, maskbits = 0; (i & pool_size) == 0; i = i << 1)
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maskbits++;
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pool->mtx_pool_shift = POINTER_BITS - maskbits;
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pool->mtx_pool_next = 0;
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for (i = 0; i < pool_size; ++i)
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mtx_init(&pool->mtx_pool_ary[i], mtx_name, NULL, opts);
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}
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struct mtx_pool *
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mtx_pool_create(const char *mtx_name, int pool_size, int opts)
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{
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struct mtx_pool *pool;
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if (pool_size <= 0 || !powerof2(pool_size)) {
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printf("WARNING: %s pool size is not a power of 2.\n",
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mtx_name);
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pool_size = 128;
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}
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MALLOC(pool, struct mtx_pool *,
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sizeof (struct mtx_pool) + ((pool_size - 1) * sizeof (struct mtx)),
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M_MTXPOOL, M_WAITOK | M_ZERO);
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mtx_pool_initialize(pool, mtx_name, pool_size, opts);
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return pool;
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}
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void
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mtx_pool_destroy(struct mtx_pool **poolp)
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{
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int i;
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struct mtx_pool *pool = *poolp;
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for (i = pool->mtx_pool_size - 1; i >= 0; --i)
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mtx_destroy(&pool->mtx_pool_ary[i]);
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FREE(pool, M_MTXPOOL);
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*poolp = NULL;
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}
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static void
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mtx_pool_setup_static(void *dummy __unused)
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{
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mtx_pool_initialize((struct mtx_pool *)&lockbuilder_pool,
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"lockbuilder mtxpool", MTX_POOL_LOCKBUILDER_SIZE,
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MTX_DEF | MTX_NOWITNESS | MTX_QUIET);
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mtxpool_lockbuilder = (struct mtx_pool *)&lockbuilder_pool;
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}
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static void
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mtx_pool_setup_dynamic(void *dummy __unused)
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{
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mtxpool_sleep = mtx_pool_create("sleep mtxpool",
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MTX_POOL_SLEEP_SIZE, MTX_DEF);
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}
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/*
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* Obtain a (shared) mutex from the pool. The returned mutex is a leaf
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* level mutex, meaning that if you obtain it you cannot obtain any other
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* mutexes until you release it. You can legally msleep() on the mutex.
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*/
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struct mtx *
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mtx_pool_alloc(struct mtx_pool *pool)
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{
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int i;
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KASSERT(pool != NULL, ("mtx_pool_alloc(): null pool"));
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/*
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* mtx_pool_next is unprotected against multiple accesses,
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* but simultaneous access by two CPUs should not be very
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* harmful.
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*/
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i = pool->mtx_pool_next;
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pool->mtx_pool_next = (i + 1) & pool->mtx_pool_mask;
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return (&pool->mtx_pool_ary[i]);
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}
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/*
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* The lockbuilder pool must be initialized early because the lockmgr
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* and sx locks depend on it. The sx locks are used in the kernel
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* memory allocator. The lockmgr subsystem is initialized by
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* SYSINIT(..., SI_SUB_LOCKMGR, ...).
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*
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* We can't call MALLOC() to dynamically allocate the sleep pool
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* until after kmeminit() has been called, which is done by
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* SYSINIT(..., SI_SUB_KMEM, ...).
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*/
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SYSINIT(mtxpooli1, SI_SUB_MTX_POOL_STATIC, SI_ORDER_FIRST,
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mtx_pool_setup_static, NULL);
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SYSINIT(mtxpooli2, SI_SUB_MTX_POOL_DYNAMIC, SI_ORDER_FIRST,
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mtx_pool_setup_dynamic, NULL);
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