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/*-
* Copyright (c) 2001 Matthew Dillon. All Rights Reserved. Copyright
* terms are as specified in the COPYRIGHT file at the base of the source
* tree.
*
* Mutex pool routines. These routines are designed to be used as short
* term leaf mutexes (e.g. the last mutex you might aquire other then
* calling msleep()). They operate using a shared pool. A mutex is chosen
* from the pool based on the supplied pointer (which may or may not be
* valid).
*
* Advantages:
* - no structural overhead. Mutexes can be associated with structures
* without adding bloat to the structures.
* - mutexes can be obtained for invalid pointers, useful when uses
* mutexes to interlock destructor ops.
* - no initialization/destructor overhead
* - can be used with msleep.
*
* Disadvantages:
* - should generally only be used as leaf mutexes
* - pool/pool dependancy ordering cannot be depended on.
* - possible L1 cache mastersip contention between cpus
*
* $FreeBSD$
*/
#include <sys/param.h>
#include <sys/proc.h>
#include <sys/kernel.h>
#include <sys/ktr.h>
#include <sys/lock.h>
#include <sys/malloc.h>
#include <sys/mutex.h>
#include <sys/systm.h>
#ifndef MTX_POOL_SIZE
#define MTX_POOL_SIZE 128
#endif
#define MTX_POOL_MASK (MTX_POOL_SIZE-1)
static struct mtx mtx_pool_ary[MTX_POOL_SIZE];
int mtx_pool_valid = 0;
/*
* Inline version of mtx_pool_find(), used to streamline our main API
* function calls.
*/
static __inline
struct mtx *
_mtx_pool_find(void *ptr)
{
int p;
p = (int)(uintptr_t)ptr;
return(&mtx_pool_ary[(p ^ (p >> 6)) & MTX_POOL_MASK]);
}
static void
mtx_pool_setup(void *dummy __unused)
{
int i;
for (i = 0; i < MTX_POOL_SIZE; ++i)
mtx_init(&mtx_pool_ary[i], "pool mutex", NULL, MTX_DEF | MTX_NOWITNESS | MTX_QUIET);
mtx_pool_valid = 1;
}
/*
* Obtain a (shared) mutex from the pool. The returned mutex is a leaf
* level mutex, meaning that if you obtain it you cannot obtain any other
* mutexes until you release it. You can legally msleep() on the mutex.
*/
struct mtx *
mtx_pool_alloc(void)
{
static int si;
return(&mtx_pool_ary[si++ & MTX_POOL_MASK]);
}
/*
* Return the (shared) pool mutex associated with the specified address.
* The returned mutex is a leaf level mutex, meaning that if you obtain it
* you cannot obtain any other mutexes until you release it. You can
* legally msleep() on the mutex.
*/
struct mtx *
mtx_pool_find(void *ptr)
{
return(_mtx_pool_find(ptr));
}
/*
* Combined find/lock operation. Lock the pool mutex associated with
* the specified address.
*/
void
mtx_pool_lock(void *ptr)
{
mtx_lock(_mtx_pool_find(ptr));
}
/*
* Combined find/unlock operation. Unlock the pool mutex associated with
* the specified address.
*/
void
mtx_pool_unlock(void *ptr)
{
mtx_unlock(_mtx_pool_find(ptr));
}
SYSINIT(mtxpooli, SI_SUB_MTX_POOL, SI_ORDER_FIRST, mtx_pool_setup, NULL)
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