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;
42 /* This handler is called when a lockwait child process has completed the lock
44 static void lockwait_handler(struct event_context *ev, struct fd_event *fde,
45 uint16_t flags, void *private_data)
47 struct lockwait_handle *h = talloc_get_type(private_data,
48 struct lockwait_handle);
49 void (*callback)(void *) = h->callback;
50 void *p = h->private_data;
51 pid_t child = h->child;
52 TDB_DATA key = h->key;
53 struct tdb_context *tdb = h->ctdb_db->ltdb->tdb;
54 TALLOC_CTX *tmp_ctx = talloc_new(ev);
57 key.dptr = talloc_memdup(tmp_ctx, key.dptr, key.dsize);
59 talloc_set_destructor(h, NULL);
61 /* If a lockwait takes excessive time to complete we want
64 l = timeval_elapsed(&h->start_time);
66 DEBUG(0,("Lockwait took %.6f seconds to complete for database %s\n", l, h->ctdb_db->db_name));
69 ctdb_latency(&h->ctdb->statistics.max_lockwait_latency, h->start_time);
70 h->ctdb->statistics.pending_lockwait_calls--;
72 /* the handle needs to go away when the context is gone - when
73 the handle goes away this implicitly closes the pipe, which
74 kills the child holding the lock */
75 talloc_steal(tmp_ctx, h);
77 if (h->ctdb->flags & CTDB_FLAG_TORTURE) {
78 if (tdb_chainlock_nonblock(tdb, key) == 0) {
79 ctdb_fatal(h->ctdb, "got chain lock while lockwait child active");
83 tdb_chainlock_mark(tdb, key);
85 tdb_chainlock_unmark(tdb, key);
88 waitpid(child, NULL, 0);
92 static int lockwait_destructor(struct lockwait_handle *h)
94 h->ctdb->statistics.pending_lockwait_calls--;
95 kill(h->child, SIGKILL);
96 waitpid(h->child, NULL, 0);
101 setup a non-blocking chainlock on a tdb record. If this function
102 returns NULL then it could not get the chainlock. Otherwise it
103 returns a opaque handle, and will call callback() once it has
104 managed to get the chainlock. You can cancel it by using talloc_free
105 on the returned handle.
107 It is the callers responsibility to unlock the chainlock once
110 struct lockwait_handle *ctdb_lockwait(struct ctdb_db_context *ctdb_db,
112 void (*callback)(void *private_data),
115 struct lockwait_handle *result;
117 pid_t parent = getpid();
119 ctdb_db->ctdb->statistics.lockwait_calls++;
120 ctdb_db->ctdb->statistics.pending_lockwait_calls++;
122 if (!(result = talloc_zero(private_data, struct lockwait_handle))) {
123 ctdb_db->ctdb->statistics.pending_lockwait_calls--;
127 ret = pipe(result->fd);
131 ctdb_db->ctdb->statistics.pending_lockwait_calls--;
135 result->child = fork();
137 if (result->child == (pid_t)-1) {
138 close(result->fd[0]);
139 close(result->fd[1]);
141 ctdb_db->ctdb->statistics.pending_lockwait_calls--;
145 result->callback = callback;
146 result->private_data = private_data;
147 result->ctdb = ctdb_db->ctdb;
148 result->ctdb_db = ctdb_db;
151 if (result->child == 0) {
153 close(result->fd[0]);
154 tdb_chainlock(ctdb_db->ltdb->tdb, key);
155 write(result->fd[1], &c, 1);
156 /* make sure we die when our parent dies */
157 while (kill(parent, 0) == 0 || errno != ESRCH) {
163 close(result->fd[1]);
164 talloc_set_destructor(result, lockwait_destructor);
166 result->fde = event_add_fd(ctdb_db->ctdb->ev, result, result->fd[0],
167 EVENT_FD_READ|EVENT_FD_AUTOCLOSE, lockwait_handler,
169 if (result->fde == NULL) {
171 ctdb_db->ctdb->statistics.pending_lockwait_calls--;
175 result->start_time = timeval_current();