120 lines
2.9 KiB
C
120 lines
2.9 KiB
C
/*-
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* Copyright (c) 2001 Matthew Dillon. All Rights Reserved. Copyright
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* terms are as specified in the COPYRIGHT file at the base of the source
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* tree.
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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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#ifndef MTX_POOL_SIZE
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#define MTX_POOL_SIZE 128
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#endif
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#define MTX_POOL_MASK (MTX_POOL_SIZE - 1)
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static struct mtx mtx_pool_ary[MTX_POOL_SIZE];
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int mtx_pool_valid = 0;
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/*
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* Inline version of mtx_pool_find(), used to streamline our main API
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* function calls.
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*/
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static __inline struct mtx *
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_mtx_pool_find(void *ptr)
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{
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int p;
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p = (int)(uintptr_t)ptr;
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return (&mtx_pool_ary[(p ^ (p >> 6)) & MTX_POOL_MASK]);
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}
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static void
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mtx_pool_setup(void *dummy __unused)
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{
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int i;
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for (i = 0; i < MTX_POOL_SIZE; ++i)
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mtx_init(&mtx_pool_ary[i], "pool mutex", NULL,
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MTX_DEF | MTX_NOWITNESS | MTX_QUIET);
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mtx_pool_valid = 1;
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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(void)
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{
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static int si;
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return (&mtx_pool_ary[si++ & MTX_POOL_MASK]);
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}
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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(void *ptr)
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{
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return (_mtx_pool_find(ptr));
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}
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/*
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* Combined find/lock operation. Lock the pool mutex associated with
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* the specified address.
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*/
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void
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mtx_pool_lock(void *ptr)
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{
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mtx_lock(_mtx_pool_find(ptr));
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}
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/*
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* Combined find/unlock operation. Unlock the pool mutex associated with
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* the specified address.
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*/
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void
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mtx_pool_unlock(void *ptr)
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{
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mtx_unlock(_mtx_pool_find(ptr));
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}
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SYSINIT(mtxpooli, SI_SUB_MTX_POOL, SI_ORDER_FIRST, mtx_pool_setup, NULL);
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