2 wait for a tdb chain lock
4 Copyright (C) Andrew Tridgell 2006
6 This program is free software; you can redistribute it and/or modify
7 it under the terms of the GNU General Public License as published by
8 the Free Software Foundation; either version 3 of the License, or
9 (at your option) any later version.
11 This program is distributed in the hope that it will be useful,
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 GNU General Public License for more details.
16 You should have received a copy of the GNU General Public License
17 along with this program; if not, see <http://www.gnu.org/licenses/>.
21 #include "lib/events/events.h"
22 #include "system/filesys.h"
23 #include "system/wait.h"
25 #include "lib/tdb/include/tdb.h"
26 #include "../include/ctdb_private.h"
29 struct lockwait_handle {
30 struct ctdb_context *ctdb;
31 struct ctdb_db_context *ctdb_db;
36 void (*callback)(void *);
38 struct timeval start_time;
41 static void lockwait_handler(struct event_context *ev, struct fd_event *fde,
42 uint16_t flags, void *private_data)
44 struct lockwait_handle *h = talloc_get_type(private_data,
45 struct lockwait_handle);
46 void (*callback)(void *) = h->callback;
47 void *p = h->private_data;
48 pid_t child = h->child;
49 TDB_DATA key = h->key;
50 struct tdb_context *tdb = h->ctdb_db->ltdb->tdb;
51 TALLOC_CTX *tmp_ctx = talloc_new(ev);
53 key.dptr = talloc_memdup(tmp_ctx, key.dptr, key.dsize);
55 talloc_set_destructor(h, NULL);
56 ctdb_latency(h->ctdb_db, "lockwait", &h->ctdb->statistics.max_lockwait_latency, h->start_time);
57 h->ctdb->statistics.pending_lockwait_calls--;
59 /* the handle needs to go away when the context is gone - when
60 the handle goes away this implicitly closes the pipe, which
61 kills the child holding the lock */
62 talloc_steal(tmp_ctx, h);
64 if (h->ctdb->flags & CTDB_FLAG_TORTURE) {
65 if (tdb_chainlock_nonblock(tdb, key) == 0) {
66 ctdb_fatal(h->ctdb, "got chain lock while lockwait child active");
70 tdb_chainlock_mark(tdb, key);
72 tdb_chainlock_unmark(tdb, key);
78 static int lockwait_destructor(struct lockwait_handle *h)
80 h->ctdb->statistics.pending_lockwait_calls--;
81 kill(h->child, SIGKILL);
86 setup a non-blocking chainlock on a tdb record. If this function
87 returns NULL then it could not get the chainlock. Otherwise it
88 returns a opaque handle, and will call callback() once it has
89 managed to get the chainlock. You can cancel it by using talloc_free
90 on the returned handle.
92 It is the callers responsibility to unlock the chainlock once
95 struct lockwait_handle *ctdb_lockwait(struct ctdb_db_context *ctdb_db,
97 void (*callback)(void *private_data),
100 struct lockwait_handle *result;
102 pid_t parent = getpid();
104 ctdb_db->ctdb->statistics.lockwait_calls++;
105 ctdb_db->ctdb->statistics.pending_lockwait_calls++;
107 if (!(result = talloc_zero(private_data, struct lockwait_handle))) {
108 ctdb_db->ctdb->statistics.pending_lockwait_calls--;
112 ret = pipe(result->fd);
116 ctdb_db->ctdb->statistics.pending_lockwait_calls--;
120 result->child = fork();
122 if (result->child == (pid_t)-1) {
123 close(result->fd[0]);
124 close(result->fd[1]);
126 ctdb_db->ctdb->statistics.pending_lockwait_calls--;
130 result->callback = callback;
131 result->private_data = private_data;
132 result->ctdb = ctdb_db->ctdb;
133 result->ctdb_db = ctdb_db;
136 if (result->child == 0) {
138 close(result->fd[0]);
139 debug_extra = talloc_asprintf(NULL, "chainlock-%s:", ctdb_db->db_name);
140 tdb_chainlock(ctdb_db->ltdb->tdb, key);
141 write(result->fd[1], &c, 1);
142 /* make sure we die when our parent dies */
143 while (kill(parent, 0) == 0 || errno != ESRCH) {
149 close(result->fd[1]);
150 set_close_on_exec(result->fd[0]);
152 DEBUG(DEBUG_DEBUG, (__location__ " Created PIPE FD:%d to child lockwait process\n", result->fd[0]));
154 talloc_set_destructor(result, lockwait_destructor);
156 result->fde = event_add_fd(ctdb_db->ctdb->ev, result, result->fd[0],
157 EVENT_FD_READ|EVENT_FD_AUTOCLOSE, lockwait_handler,
159 if (result->fde == NULL) {
161 ctdb_db->ctdb->statistics.pending_lockwait_calls--;
165 result->start_time = timeval_current();