1 /* Copyright (c) 1998, 1999 Free Software Foundation, Inc.
2 This file is part of the GNU C Library.
3 Contributed by Ulrich Drepper <drepper@cygnus.com>, 1998.
5 The GNU C Library is free software; you can redistribute it and/or
6 modify it under the terms of the GNU Library General Public License as
7 published by the Free Software Foundation; either version 2 of the
8 License, or (at your option) any later version.
10 The GNU C Library is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 Library General Public License for more details.
15 You should have received a copy of the GNU Library General Public
16 License along with the GNU C Library; see the file COPYING.LIB. If not,
17 write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
18 Boston, MA 02111-1307, USA. */
20 #include <atomicity.h>
26 #include <arpa/inet.h>
27 #include <rpcsvc/nis.h>
28 #include <sys/param.h>
35 /* Search the cache for a matching entry and return it when found. If
36 this fails search the negative cache and return (void *) -1 if this
37 search was successful. Otherwise return NULL.
39 This function must be called with the read-lock held. */
41 cache_search (int type, void *key, size_t len, struct database *table)
43 unsigned long int hash = __nis_hash (key, len) % table->module;
44 struct hashentry *work;
46 work = table->array[hash];
50 if (type == work->type
51 && len == work->len && memcmp (key, work->key, len) == 0)
53 /* We found the entry. Increment the appropriate counter. */
54 if (work->data == (void *) -1)
68 /* Add a new entry to the cache. The return value is zero if the function
71 This function must be called with the read-lock held.
73 We modify the table but we nevertheless only acquire a read-lock.
74 This is ok since we use operations which would be safe even without
75 locking, given that the `prune_cache' function never runs. Using
76 the readlock reduces the chance of conflicts. */
78 cache_add (int type, void *key, size_t len, const void *packet, size_t total,
79 void *data, int last, time_t t, struct database *table)
81 unsigned long int hash = __nis_hash (key, len) % table->module;
82 struct hashentry *newp;
84 newp = malloc (sizeof (struct hashentry));
86 error (EXIT_FAILURE, errno, _("while allocating hash table entry"));
93 newp->packet = packet;
98 /* Put the new entry in the first position. */
100 newp->next = table->array[hash];
101 while (! compare_and_swap ((volatile long int *) &table->array[hash],
102 (long int) newp->next, (long int) newp));
104 /* Update the statistics. */
105 if (data == (void *) -1)
111 /* Walk through the table and remove all entries which lifetime ended.
113 We have a problem here. To actually remove the entries we must get
114 the write-lock. But since we want to keep the time we have the
115 lock as short as possible we cannot simply acquire the lock when we
116 start looking for timedout entries.
118 Therefore we do it in two stages: first we look for entries which
119 must be invalidated and remember them. Then we get the lock and
120 actually remove them. This is complicated by the way we have to
121 free the data structures since some hash table entries share the same
124 prune_cache (struct database *table, time_t now)
126 size_t cnt = table->module;
129 size_t first = cnt + 1;
132 /* If we check for the modification of the underlying file we invalidate
133 the entries also in this case. */
134 if (table->check_file)
138 if (stat (table->filename, &st) < 0)
141 /* We cannot stat() the file, disable file checking. */
142 dbg_log (_("cannot stat() file `%s': %s"),
143 table->filename, strerror_r (errno, buf, sizeof (buf)));
144 table->check_file = 0;
148 if (st.st_mtime != table->file_mtime)
149 /* The file changed. Invalidate all entries. */
154 /* We run through the table and find values which are not valid anymore.
156 Note that for the initial step, finding the entries to be removed,
157 we don't need to get any lock. It is at all timed assured that the
158 linked lists are set up correctly and that no second thread prunes
162 struct hashentry *runp = table->array[--cnt];
168 if (runp->timeout < now)
172 first = MIN (first, cnt);
173 last = MAX (last, cnt);
182 struct hashentry *head = NULL;
184 /* Now we have to get the write lock since we are about to modify
186 pthread_rwlock_wrlock (&table->lock);
188 while (first <= last)
192 struct hashentry *runp;
194 while (table->array[first]->timeout < now)
196 table->array[first]->dellist = head;
197 head = table->array[first];
198 table->array[first] = head->next;
199 if (--mark[first] == 0)
203 runp = table->array[first];
204 while (mark[first] > 0)
206 if (runp->next->timeout < now)
208 runp->next->dellist = head;
210 runp->next = head->next;
221 pthread_rwlock_unlock (&table->lock);
223 /* And another run to free the data. */
226 struct hashentry *old = head;
230 char buf[INET6_ADDRSTRLEN];
233 if ((old->type == GETHOSTBYADDR || old->type == GETHOSTBYADDRv6)
234 && (old->last || old->data == (void *) -1))
236 inet_ntop (old->type == GETHOSTBYADDR ? AF_INET : AF_INET6,
237 old->key, buf, sizeof (buf));
241 str = old->last ? old->key : (old->data == (void *) -1
244 dbg_log ("remove %s entry \"%s\"", serv2str[old->type], str);
247 /* Free the data structures. */
248 if (old->data == (void *) -1)
253 head = head->dellist;
257 while (head != NULL);