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 2 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, write to the Free Software
18 Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
22 #include "lib/events/events.h"
23 #include "system/filesys.h"
24 #include "system/wait.h"
26 #include "lib/tdb/include/tdb.h"
27 #include "../include/ctdb_private.h"
30 struct lockwait_handle {
31 struct ctdb_context *ctdb;
32 struct ctdb_db_context *ctdb_db;
37 void (*callback)(void *);
39 struct timeval start_time;
42 static void lockwait_handler(struct event_context *ev, struct fd_event *fde,
43 uint16_t flags, void *private_data)
45 struct lockwait_handle *h = talloc_get_type(private_data,
46 struct lockwait_handle);
47 void (*callback)(void *) = h->callback;
48 void *p = h->private_data;
49 pid_t child = h->child;
50 TDB_DATA key = h->key;
51 struct tdb_context *tdb = h->ctdb_db->ltdb->tdb;
52 TALLOC_CTX *tmp_ctx = talloc_new(ev);
54 key.dptr = talloc_memdup(tmp_ctx, key.dptr, key.dsize);
56 talloc_set_destructor(h, NULL);
57 ctdb_latency(&h->ctdb->statistics.max_lockwait_latency, h->start_time);
58 h->ctdb->statistics.pending_lockwait_calls--;
60 /* the handle needs to go away when the context is gone - when
61 the handle goes away this implicitly closes the pipe, which
62 kills the child holding the lock */
63 talloc_steal(tmp_ctx, h);
65 if (h->ctdb->flags & CTDB_FLAG_TORTURE) {
66 if (tdb_chainlock_nonblock(tdb, key) == 0) {
67 ctdb_fatal(h->ctdb, "got chain lock while lockwait child active");
71 tdb_chainlock_mark(tdb, key);
73 tdb_chainlock_unmark(tdb, key);
76 waitpid(child, NULL, 0);
80 static int lockwait_destructor(struct lockwait_handle *h)
82 h->ctdb->statistics.pending_lockwait_calls--;
83 kill(h->child, SIGKILL);
84 waitpid(h->child, NULL, 0);
89 setup a non-blocking chainlock on a tdb record. If this function
90 returns NULL then it could not get the chainlock. Otherwise it
91 returns a opaque handle, and will call callback() once it has
92 managed to get the chainlock. You can cancel it by using talloc_free
93 on the returned handle.
95 It is the callers responsibility to unlock the chainlock once
98 struct lockwait_handle *ctdb_lockwait(struct ctdb_db_context *ctdb_db,
100 void (*callback)(void *private_data),
103 struct lockwait_handle *result;
105 pid_t parent = getpid();
107 ctdb_db->ctdb->statistics.lockwait_calls++;
108 ctdb_db->ctdb->statistics.pending_lockwait_calls++;
110 if (!(result = talloc_zero(private_data, struct lockwait_handle))) {
111 ctdb_db->ctdb->statistics.pending_lockwait_calls--;
115 ret = pipe(result->fd);
119 ctdb_db->ctdb->statistics.pending_lockwait_calls--;
123 result->child = fork();
125 if (result->child == (pid_t)-1) {
126 close(result->fd[0]);
127 close(result->fd[1]);
129 ctdb_db->ctdb->statistics.pending_lockwait_calls--;
133 result->callback = callback;
134 result->private_data = private_data;
135 result->ctdb = ctdb_db->ctdb;
136 result->ctdb_db = ctdb_db;
139 if (result->child == 0) {
141 close(result->fd[0]);
142 tdb_chainlock(ctdb_db->ltdb->tdb, key);
143 write(result->fd[1], &c, 1);
144 /* make sure we die when our parent dies */
145 while (kill(parent, 0) == 0 || errno != ESRCH) {
151 close(result->fd[1]);
152 talloc_set_destructor(result, lockwait_destructor);
154 result->fde = event_add_fd(ctdb_db->ctdb->ev, result, result->fd[0],
155 EVENT_FD_READ|EVENT_FD_AUTOCLOSE, lockwait_handler,
157 if (result->fde == NULL) {
159 ctdb_db->ctdb->statistics.pending_lockwait_calls--;
163 result->start_time = timeval_current();