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kern_uidinfo.c revision 1.3 
      1 /*	$NetBSD: kern_uidinfo.c,v 1.3 2008/10/14 09:17:23 ad Exp $	*/
      2 
      3 /*-
      4  * Copyright (c) 1982, 1986, 1991, 1993
      5  *	The Regents of the University of California.  All rights reserved.
      6  * (c) UNIX System Laboratories, Inc.
      7  * All or some portions of this file are derived from material licensed
      8  * to the University of California by American Telephone and Telegraph
      9  * Co. or Unix System Laboratories, Inc. and are reproduced herein with
     10  * the permission of UNIX System Laboratories, Inc.
     11  *
     12  * Redistribution and use in source and binary forms, with or without
     13  * modification, are permitted provided that the following conditions
     14  * are met:
     15  * 1. Redistributions of source code must retain the above copyright
     16  *    notice, this list of conditions and the following disclaimer.
     17  * 2. Redistributions in binary form must reproduce the above copyright
     18  *    notice, this list of conditions and the following disclaimer in the
     19  *    documentation and/or other materials provided with the distribution.
     20  * 3. Neither the name of the University nor the names of its contributors
     21  *    may be used to endorse or promote products derived from this software
     22  *    without specific prior written permission.
     23  *
     24  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     25  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     26  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     27  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     28  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     29  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     30  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     31  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     32  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     33  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     34  * SUCH DAMAGE.
     35  */
     36 
     37 #include <sys/cdefs.h>
     38 __KERNEL_RCSID(0, "$NetBSD: kern_uidinfo.c,v 1.3 2008/10/14 09:17:23 ad Exp $");
     39 
     40 #include <sys/param.h>
     41 #include <sys/systm.h>
     42 #include <sys/kmem.h>
     43 #include <sys/proc.h>
     44 #include <sys/atomic.h>
     45 #include <sys/uidinfo.h>
     46 
     47 static SLIST_HEAD(uihashhead, uidinfo) *uihashtbl;
     48 static u_long 		uihash;
     49 
     50 #define	UIHASH(uid)	(&uihashtbl[(uid) & uihash])
     51 
     52 void
     53 uid_init(void)
     54 {
     55 
     56 	/*
     57 	 * In case of MP system, SLIST_FOREACH would force a cache line
     58 	 * write-back for every modified 'uidinfo', thus we try to keep the
     59 	 * lists short.
     60 	 */
     61 	const u_int uihash_sz = (maxproc > 1 ? 1024 : 64);
     62 
     63 	uihashtbl = hashinit(uihash_sz, HASH_SLIST, true, &uihash);
     64 
     65 	/*
     66 	 * Ensure that uid 0 is always in the user hash table, as
     67 	 * sbreserve() expects it available from interrupt context.
     68 	 */
     69 	(void)uid_find(0);
     70 }
     71 
     72 struct uidinfo *
     73 uid_find(uid_t uid)
     74 {
     75 	struct uidinfo *uip, *uip_first, *newuip;
     76 	struct uihashhead *uipp;
     77 
     78 	uipp = UIHASH(uid);
     79 	newuip = NULL;
     80 
     81 	/*
     82 	 * To make insertion atomic, abstraction of SLIST will be violated.
     83 	 */
     84 	uip_first = uipp->slh_first;
     85  again:
     86 	SLIST_FOREACH(uip, uipp, ui_hash) {
     87 		if (uip->ui_uid != uid)
     88 			continue;
     89 		if (newuip != NULL)
     90 			kmem_free(newuip, sizeof(*newuip));
     91 		return uip;
     92 	}
     93 	if (newuip == NULL)
     94 		newuip = kmem_zalloc(sizeof(*newuip), KM_SLEEP);
     95 	newuip->ui_uid = uid;
     96 
     97 	/*
     98 	 * If atomic insert is unsuccessful, another thread might be
     99 	 * allocated this 'uid', thus full re-check is needed.
    100 	 */
    101 	newuip->ui_hash.sle_next = uip_first;
    102 	membar_producer();
    103 	uip = atomic_cas_ptr(&uipp->slh_first, uip_first, newuip);
    104 	if (uip != uip_first) {
    105 		uip_first = uip;
    106 		goto again;
    107 	}
    108 
    109 	return newuip;
    110 }
    111 
    112 /*
    113  * Change the count associated with number of processes
    114  * a given user is using.
    115  */
    116 int
    117 chgproccnt(uid_t uid, int diff)
    118 {
    119 	struct uidinfo *uip;
    120 	long proccnt;
    121 
    122 	uip = uid_find(uid);
    123 	proccnt = atomic_add_long_nv(&uip->ui_proccnt, diff);
    124 	KASSERT(proccnt >= 0);
    125 	return proccnt;
    126 }
    127 
    128 int
    129 chgsbsize(struct uidinfo *uip, u_long *hiwat, u_long to, rlim_t xmax)
    130 {
    131 	rlim_t nsb;
    132 	const long diff = to - *hiwat;
    133 
    134 	nsb = (rlim_t)atomic_add_long_nv((long *)&uip->ui_sbsize, diff);
    135 	if (diff > 0 && nsb > xmax) {
    136 		atomic_add_long((long *)&uip->ui_sbsize, -diff);
    137 		return 0;
    138 	}
    139 	*hiwat = to;
    140 	KASSERT(nsb >= 0);
    141 	return 1;
    142 }
    143