/*
Unix SMB/CIFS implementation.
trivial database library
Copyright (C) Volker Lendecke 2012,2013
Copyright (C) Stefan Metzmacher 2013,2014
Copyright (C) Michael Adam 2014
** NOTE! The following LGPL license applies to the tdb
** library. This does NOT imply that all of Samba is released
** under the LGPL
This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 3 of the License, or (at your option) any later version.
This library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with this library; if not, see <http://www.gnu.org/licenses/>.
*/
#include "tdb_private.h"
#include "system/threads.h"
#ifdef USE_TDB_MUTEX_LOCKING
/*
* If we run with mutexes, we store the "struct tdb_mutexes" at the
* beginning of the file. We store an additional tdb_header right
* beyond the mutex area, page aligned. All the offsets within the tdb
* are relative to the area behind the mutex area. tdb->map_ptr points
* behind the mmap area as well, so the read and write path in the
* mutex case can remain unchanged.
*
* Early in the mutex development the mutexes were placed between the hash
* chain pointers and the real tdb data. This had two drawbacks: First, it
* made pointer calculations more complex. Second, we had to mmap the mutex
* area twice. One was the normal map_ptr in the tdb. This frequently changed
* from within tdb_oob. At least the Linux glibc robust mutex code assumes
* constant pointers in memory, so a constantly changing mmap area destroys
* the mutex list. So we had to mmap the first bytes of the file with a second
* mmap call. With that scheme, very weird errors happened that could be
* easily fixed by doing the mutex mmap in a second file. It seemed that
* mapping the same memory area twice does not end up in accessing the same
* physical page, looking at the mutexes in gdb it seemed that old data showed
* up after some re-mapping. To avoid a separate mutex file, the code now puts
* the real content of the tdb file after the mutex area. This way we do not
* have overlapping mmap areas, the mutex area is mmapped once and not
* changed, the tdb data area's mmap is constantly changed but does not
* overlap.
*/
struct tdb_mutexes {
struct tdb_header hdr;
/* protect allrecord_lock */
pthread_mutex_t allrecord_mutex;
/*
* F_UNLCK: free,
* F_RDLCK: shared,
* F_WRLCK: exclusive
*/
short int allrecord_lock;
/*
* Index 0 is the freelist mutex, followed by
* one mutex per hashchain.
*/
pthread_mutex_t hashchains[1];
};
bool tdb_have_mutexes(struct tdb_context *tdb)
{
return ((tdb->feature_flags & TDB_FEATURE_FLAG_MUTEX) != 0);
}
size_t tdb_mutex_size(struct tdb_context *tdb)
{
size_t mutex_size;
if (!tdb_have_mutexes(tdb)) {
return 0;
}
mutex_size = sizeof(struct tdb_mutexes);
mutex_size += tdb->hash_size * sizeof(pthread_mutex_t);
return TDB_ALIGN(mutex_size, tdb->page_size);
}
/*
* Get the index for a chain mutex
*/
static bool tdb_mutex_index(struct tdb_context *tdb, off_t off, off_t len,
unsigned *idx)
{
/*
* Weird but true: We fcntl lock 1 byte at an offset 4 bytes before
* the 4 bytes of the freelist start and the hash chain that is about
* to be locked. See lock_offset() where the freelist is -1 vs the
* "+1" in TDB_HASH_TOP(). Because the mutex array is represented in
* the tdb file itself as data, we need to adjust the offset here.
*/
const off_t freelist_lock_ofs = FREELIST_TOP - sizeof(tdb_off_t);
if (!tdb_have_mutexes(tdb)) {
return false;
}
if (len != 1) {
/* Possibly the allrecord lock */
return false;
}
if (off < freelist_lock_ofs) {
/* One of the special locks */
return false;
}
if (tdb->hash_size == 0) {
/* tdb not initialized yet, called from tdb_open_ex() */
return false;
}
if (off >= TDB_DATA_START(tdb->hash_size)) {
/* Single record lock from traverses */
return false;
}
/*
* Now we know it's a freelist or hash chain lock. Those are always 4
* byte aligned. Paranoia check.
*/
if ((off % sizeof(tdb_off_t)) != 0) {
abort();
}
/*
* Re-index the fcntl offset into an offset into the mutex array
*/
off -= freelist_lock_ofs; /* rebase to index 0 */
off /= sizeof(tdb_off_t); /* 0 for freelist 1-n for hashchain */
*idx = off;
return true;
}
static bool tdb_have_mutex_chainlocks(struct tdb_context *tdb)
{
size_t i;
for (i=0; i < tdb->num_lockrecs; i++) {
bool ret;
unsigned idx;
ret = tdb_mutex_index(tdb,
tdb->lockrecs[i].off,
tdb->lockrecs[i].count,
&idx);
if (!ret) {
continue;
}
if (idx == 0) {
/* this is the freelist mutex */
continue;
}
return true;
}
return false;
}
static int chain_mutex_lock(pthread_mutex_t *m, bool waitflag)
{
int ret;
if (waitflag) {
ret = pthread_mutex_lock(m);
} else {
ret = pthread_mutex_trylock(m);
}
if (ret != EOWNERDEAD) {
return ret;
}
/*
* For chainlocks, we don't do any cleanup (yet?)
*/
return pthread_mutex_consistent(m);
}
static int allrecord_mutex_lock(struct tdb_mutexes *m, bool waitflag)
{
int ret;
if (waitflag) {
ret = pthread_mutex_lock(&m->allrecord_mutex);
} else {
ret = pthread_mutex_trylock(&m->allrecord_mutex);
}
if (ret != EOWNERDEAD) {
return ret;
}
/*
* The allrecord lock holder died. We need to reset the allrecord_lock
* to F_UNLCK. This should also be the indication for
* tdb_needs_recovery.
*/
m->allrecord_lock = F_UNLCK;
return pthread_mutex_consistent(&m->allrecord_mutex);
}
bool tdb_mutex_lock(struct tdb_context *tdb, int rw, off_t off, off_t len,
bool waitflag, int *pret)
{
struct tdb_mutexes *m = tdb->mutexes;
pthread_mutex_t *chain;
int ret;
unsigned idx;
bool allrecord_ok;
if (!tdb_mutex_index(tdb, off, len, &idx)) {
return false;
}
chain = &m->hashchains[idx];
again:
ret = chain_mutex_lock(chain, waitflag);
if (ret == EBUSY) {
ret = EAGAIN;
}
if (ret != 0) {
errno = ret;
goto fail;
}
if (idx == 0) {
/*
* This is a freelist lock, which is independent to
* the allrecord lock. So we're done once we got the
* freelist mutex.
*/
*pret = 0;
return true;
}
if (tdb_have_mutex_chainlocks(tdb)) {
/*
* We can only check the allrecord lock once. If we do it with
* one chain mutex locked, we will deadlock with the allrecord
* locker process in the following way: We lock the first hash
* chain, we check for the allrecord lock. We keep the hash
* chain locked. Then the allrecord locker locks the
* allrecord_mutex. It walks the list of chain mutexes,
* locking them all in sequence. Meanwhile, we have the chain
* mutex locked, so the allrecord locker blocks trying to lock
* our chain mutex. Then we come in and try to lock the second
* chain lock, which in most cases will be the freelist. We
* see that the allrecord lock is locked and put ourselves on
* the allrecord_mutex. This will never be signalled though
* because the allrecord locker waits for us to give up the
* chain lock.
*/
*pret = 0;
return true;
}
/*
* Check if someone is has the allrecord lock: queue if so.
*/
allrecord_ok = false;
if (m->allrecord_lock == F_UNLCK) {
/*
* allrecord lock not taken
*/
allrecord_ok = true;
}
if ((m->allrecord_lock == F_RDLCK) && (rw == F_RDLCK)) {
/*
* allrecord shared lock taken, but we only want to read
*/
allrecord_ok = true;
}
if (allrecord_ok) {
*pret = 0;
return true;
}
ret = pthread_mutex_unlock(chain);
if (ret != 0) {
TDB_LOG((tdb, TDB_DEBUG_FATAL, "pthread_mutex_unlock"
"(chain_mutex) failed: %s\n", strerror(ret)));
errno = ret;
goto fail;
}
ret = allrecord_mutex_lock(m, waitflag);
if (ret == EBUSY) {
ret = EAGAIN;
}
if (ret != 0) {
if (waitflag || (ret != EAGAIN)) {
TDB_LOG((tdb, TDB_DEBUG_FATAL, "pthread_mutex_%slock"
"(allrecord_mutex) failed: %s\n",
waitflag ? "" : "try_", strerror(ret)));
}
errno = ret;
goto fail;
}
ret = pthread_mutex_unlock(&m->allrecord_mutex);
if (ret != 0) {
TDB_LOG((tdb, TDB_DEBUG_FATAL, "pthread_mutex_unlock"
"(allrecord_mutex) failed: %s\n", strerror(ret)));
errno = ret;
goto fail;
}
goto again;
fail:
*pret = -1;
return true;
}
bool tdb_mutex_unlock(struct tdb_context *tdb, int rw, off_t off, off_t len,
int *pret)
{
struct tdb_mutexes *m = tdb->mutexes;
pthread_mutex_t *chain;
int ret;
unsigned idx;
if (!tdb_mutex_index(tdb, off, len, &idx)) {
return false;
}
chain = &m->hashchains[idx];
ret = pthread_mutex_unlock(chain);
if (ret == 0) {
*pret = 0;
return true;
}
errno = ret;
*pret = -1;
return true;
}
int tdb_mutex_allrecord_lock(struct tdb_context *tdb, int ltype,
enum tdb_lock_flags flags)
{
struct tdb_mutexes *m = tdb->mutexes;
int ret;
uint32_t i;
bool waitflag = (flags & TDB_LOCK_WAIT);
int saved_errno;
if (tdb->flags & TDB_NOLOCK) {
return 0;
}
if (flags & TDB_LOCK_MARK_ONLY) {
return 0;
}
ret = allrecord_mutex_lock(m, waitflag);
if (!waitflag && (ret == EBUSY)) {
errno = EAGAIN;
tdb->ecode = TDB_ERR_LOCK;
return -1;
}
if (ret != 0) {
if (!(flags & TDB_LOCK_PROBE)) {
TDB_LOG((tdb, TDB_DEBUG_TRACE,
"allrecord_mutex_lock() failed: %s\n",
strerror(ret)));
}
tdb->ecode = TDB_ERR_LOCK;
return -1;
}
if (m->allrecord_lock != F_UNLCK) {
TDB_LOG((tdb, TDB_DEBUG_FATAL, "allrecord_lock == %d\n",
(int)m->allrecord_lock));
goto fail_unlock_allrecord_mutex;
}
m->allrecord_lock = (ltype == F_RDLCK) ? F_RDLCK : F_WRLCK;
for (i=0; i<tdb->hash_size; i++) {
/* ignore hashchains[0], the freelist */
pthread_mutex_t *chain = &m->hashchains[i+1];
ret = chain_mutex_lock(chain, waitflag);
if (!waitflag && (ret == EBUSY)) {
errno = EAGAIN;
goto fail_unroll_allrecord_lock;
}
if (ret != 0) {
if (!(flags & TDB_LOCK_PROBE)) {
TDB_LOG((tdb, TDB_DEBUG_TRACE,
"chain_mutex_lock() failed: %s\n",
strerror(ret)));
}
errno = ret;
goto fail_unroll_allrecord_lock;
}
ret = pthread_mutex_unlock(chain);
if (ret != 0) {
TDB_LOG((tdb, TDB_DEBUG_FATAL, "pthread_mutex_unlock"
"(chainlock) failed: %s\n", strerror(ret)));
errno = ret;
goto fail_unroll_allrecord_lock;
}
}
/*
* We leave this routine with m->allrecord_mutex locked
*/
return 0;
fail_unroll_allrecord_lock:
m->allrecord_lock = F_UNLCK;
fail_unlock_allrecord_mutex:
saved_errno = errno;
ret = pthread_mutex_unlock(&m->allrecord_mutex);
if (ret != 0) {
TDB_LOG((tdb, TDB_DEBUG_FATAL, "pthread_mutex_unlock"
"(allrecord_mutex) failed: %s\n", strerror(ret)));
}
errno = saved_errno;
tdb->ecode = TDB_ERR_LOCK;
return -1;
}
int tdb_mutex_allrecord_upgrade(struct tdb_context *tdb)
{
struct tdb_mutexes *m = tdb->mutexes;
int ret;
uint32_t i;
if (tdb->flags & TDB_NOLOCK) {
return 0;
}
/*
* Our only caller tdb_allrecord_upgrade()
* garantees that we already own the allrecord lock.
*
* Which means m->allrecord_mutex is still locked by us.
*/
if (m->allrecord_lock != F_RDLCK) {
tdb->ecode = TDB_ERR_LOCK;
TDB_LOG((tdb, TDB_DEBUG_FATAL, "allrecord_lock == %d\n",
(int)m->allrecord_lock));
return -1;
}
m->allrecord_lock = F_WRLCK;
for (i=0; i<tdb->hash_size; i++) {
/* ignore hashchains[0], the freelist */
pthread_mutex_t *chain = &m->hashchains[i+1];
ret = chain_mutex_lock(chain, true);
if (ret != 0) {
TDB_LOG((tdb, TDB_DEBUG_FATAL, "pthread_mutex_lock"
"(chainlock) failed: %s\n", strerror(ret)));
goto fail_unroll_allrecord_lock;
}
ret = pthread_mutex_unlock(chain);
if (ret != 0) {
TDB_LOG((tdb, TDB_DEBUG_FATAL, "pthread_mutex_unlock"
"(chainlock) failed: %s\n", strerror(ret)));
goto fail_unroll_allrecord_lock;
}
}
return 0;
fail_unroll_allrecord_lock:
m->allrecord_lock = F_RDLCK;
tdb->ecode = TDB_ERR_LOCK;
return -1;
}
void tdb_mutex_allrecord_downgrade(struct tdb_context *tdb)
{
struct tdb_mutexes *m = tdb->mutexes;
/*
* Our only caller tdb_allrecord_upgrade() (in the error case)
* garantees that we already own the allrecord lock.
*
* Which means m->allrecord_mutex is still locked by us.
*/
if (m->allrecord_lock != F_WRLCK) {
TDB_LOG((tdb, TDB_DEBUG_FATAL, "allrecord_lock == %d\n",
(int)m->allrecord_lock));
return;
}
m->allrecord_lock = F_RDLCK;
return;
}
int tdb_mutex_allrecord_unlock(struct tdb_context *tdb)
{
struct tdb_mutexes *m = tdb->mutexes;
short old;
int ret;
if (tdb->flags & TDB_NOLOCK) {
return 0;
}
/*
* Our only callers tdb_allrecord_unlock() and
* tdb_allrecord_lock() (in the error path)
* garantee that we already own the allrecord lock.
*
* Which means m->allrecord_mutex is still locked by us.
*/
if ((m->allrecord_lock != F_RDLCK) && (m->allrecord_lock != F_WRLCK)) {
TDB_LOG((tdb, TDB_DEBUG_FATAL, "allrecord_lock == %d\n",
(int)m->allrecord_lock));
return -1;
}
old = m->allrecord_lock;
m->allrecord_lock = F_UNLCK;
ret = pthread_mutex_unlock(&m->allrecord_mutex);
if (ret != 0) {
m->allrecord_lock = old;
TDB_LOG((tdb, TDB_DEBUG_FATAL, "pthread_mutex_unlock"
"(allrecord_mutex) failed: %s\n", strerror(ret)));
return -1;
}
return 0;
}
int tdb_mutex_init(struct tdb_context *tdb)
{
struct tdb_mutexes *m;
pthread_mutexattr_t ma;
int i, ret;
ret = tdb_mutex_mmap(tdb);
if (ret == -1) {
return -1;
}
m = tdb->mutexes;
ret = pthread_mutexattr_init(&ma);
if (ret != 0) {
goto fail_munmap;
}
ret = pthread_mutexattr_settype(&ma, PTHREAD_MUTEX_ERRORCHECK);
if (ret != 0) {
goto fail;
}
ret = pthread_mutexattr_setpshared(&ma, PTHREAD_PROCESS_SHARED);
if (ret != 0) {
goto fail;
}
ret = pthread_mutexattr_setrobust(&ma, PTHREAD_MUTEX_ROBUST);
if (ret != 0) {
goto fail;
}
for (i=0; i<tdb->hash_size+1; i++) {
pthread_mutex_t *chain = &m->hashchains[i];
ret = pthread_mutex_init(chain, &ma);
if (ret != 0) {
goto fail;
}
}
m->allrecord_lock = F_UNLCK;
ret = pthread_mutex_init(&m->allrecord_mutex, &ma);
if (ret != 0) {
goto fail;
}
ret = 0;
fail:
pthread_mutexattr_destroy(&ma);
fail_munmap:
if (ret == 0) {
return 0;
}
tdb_mutex_munmap(tdb);
errno = ret;
return -1;
}
int tdb_mutex_mmap(struct tdb_context *tdb)
{
size_t len;
void *ptr;
len = tdb_mutex_size(tdb);
if (len == 0) {
return 0;
}
if (tdb->mutexes != NULL) {
return 0;
}
ptr = mmap(NULL, len, PROT_READ|PROT_WRITE, MAP_SHARED|MAP_FILE,
tdb->fd, 0);
if (ptr == MAP_FAILED) {
return -1;
}
tdb->mutexes = (struct tdb_mutexes *)ptr;
return 0;
}
int tdb_mutex_munmap(struct tdb_context *tdb)
{
size_t len;
int ret;
len = tdb_mutex_size(tdb);
if (len == 0) {
return 0;
}
ret = munmap(tdb->mutexes, len);
if (ret == -1) {
return -1;
}
tdb->mutexes = NULL;
return 0;
}
static bool tdb_mutex_locking_cached;
static bool tdb_mutex_locking_supported(void)
{
pthread_mutexattr_t ma;
pthread_mutex_t m;
int ret;
static bool initialized;
if (initialized) {
return tdb_mutex_locking_cached;
}
initialized = true;
ret = pthread_mutexattr_init(&ma);
if (ret != 0) {
return false;
}
ret = pthread_mutexattr_settype(&ma, PTHREAD_MUTEX_ERRORCHECK);
if (ret != 0) {
goto cleanup_ma;
}
ret = pthread_mutexattr_setpshared(&ma, PTHREAD_PROCESS_SHARED);
if (ret != 0) {
goto cleanup_ma;
}
ret = pthread_mutexattr_setrobust(&ma, PTHREAD_MUTEX_ROBUST);
if (ret != 0) {
goto cleanup_ma;
}
ret = pthread_mutex_init(&m, &ma);
if (ret != 0) {
goto cleanup_ma;
}
ret = pthread_mutex_lock(&m);
if (ret != 0) {
goto cleanup_m;
}
/*
* This makes sure we have real mutexes
* from a threading library instead of just
* stubs from libc.
*/
ret = pthread_mutex_lock(&m);
if (ret != EDEADLK) {
goto cleanup_lock;
}
ret = pthread_mutex_unlock(&m);
if (ret != 0) {
goto cleanup_m;
}
tdb_mutex_locking_cached = true;
goto cleanup_m;
cleanup_lock:
pthread_mutex_unlock(&m);
cleanup_m:
pthread_mutex_destroy(&m);
cleanup_ma:
pthread_mutexattr_destroy(&ma);
return tdb_mutex_locking_cached;
}
static void (*tdb_robust_mutext_old_handler)(int) = SIG_ERR;
static pid_t tdb_robust_mutex_pid = -1;
static bool tdb_robust_mutex_setup_sigchild(void (*handler)(int),
void (**p_old_handler)(int))
{
#ifdef HAVE_SIGACTION
struct sigaction act;
struct sigaction oldact;
memset(&act, '\0', sizeof(act));
act.sa_handler = handler;
#ifdef SA_RESTART
act.sa_flags = SA_RESTART;
#endif
sigemptyset(&act.sa_mask);
sigaddset(&act.sa_mask, SIGCHLD);
sigaction(SIGCHLD, &act, &oldact);
if (p_old_handler) {
*p_old_handler = oldact.sa_handler;
}
return true;
#else /* !HAVE_SIGACTION */
return false;
#endif
}
static void tdb_robust_mutex_handler(int sig)
{
pid_t child_pid = tdb_robust_mutex_pid;
if (child_pid != -1) {
pid_t pid;
pid = waitpid(child_pid, NULL, WNOHANG);
if (pid == -1) {
switch (errno) {
case ECHILD:
tdb_robust_mutex_pid = -1;
return;
default:
return;
}
}
if (pid == child_pid) {
tdb_robust_mutex_pid = -1;
return;
}
}
if (tdb_robust_mutext_old_handler == SIG_DFL) {
return;
}
if (tdb_robust_mutext_old_handler == SIG_IGN) {
return;
}
if (tdb_robust_mutext_old_handler == SIG_ERR) {
return;
}
tdb_robust_mutext_old_handler(sig);
}
static void tdb_robust_mutex_wait_for_child(pid_t *child_pid)
{
int options = WNOHANG;
if (*child_pid == -1) {
return;
}
while (tdb_robust_mutex_pid > 0) {
pid_t pid;
/*
* First we try with WNOHANG, as the process might not exist
* anymore. Once we've sent SIGKILL we block waiting for the
* exit.
*/
pid = waitpid(*child_pid, NULL, options);
if (pid == -1) {
if (errno == EINTR) {
continue;
} else if (errno == ECHILD) {
break;
} else {
abort();
}
}
if (pid == *child_pid) {
break;
}
kill(*child_pid, SIGKILL);
options = 0;
}
tdb_robust_mutex_pid = -1;
*child_pid = -1;
}
_PUBLIC_ bool tdb_runtime_check_for_robust_mutexes(void)
{
void *ptr = NULL;
pthread_mutex_t *m = NULL;
pthread_mutexattr_t ma;
int ret = 1;
int pipe_down[2] = { -1, -1 };
int pipe_up[2] = { -1, -1 };
ssize_t nread;
char c = 0;
bool ok;
static bool initialized;
pid_t saved_child_pid = -1;
bool cleanup_ma = false;
if (initialized) {
return tdb_mutex_locking_cached;
}
initialized = true;
ok = tdb_mutex_locking_supported();
if (!ok) {
return false;
}
tdb_mutex_locking_cached = false;
ptr = mmap(NULL, sizeof(pthread_mutex_t), PROT_READ|PROT_WRITE,
MAP_SHARED|MAP_ANON, -1 /* fd */, 0);
if (ptr == MAP_FAILED) {
return false;
}
ret = pipe(pipe_down);
if (ret != 0) {
goto cleanup;
}
ret = pipe(pipe_up);
if (ret != 0) {
goto cleanup;
}
ret = pthread_mutexattr_init(&ma);
if (ret != 0) {
goto cleanup;
}
cleanup_ma = true;
ret = pthread_mutexattr_settype(&ma, PTHREAD_MUTEX_ERRORCHECK);
if (ret != 0) {
goto cleanup;
}
ret = pthread_mutexattr_setpshared(&ma, PTHREAD_PROCESS_SHARED);
if (ret != 0) {
goto cleanup;
}
ret = pthread_mutexattr_setrobust(&ma, PTHREAD_MUTEX_ROBUST);
if (ret != 0) {
goto cleanup;
}
ret = pthread_mutex_init(ptr, &ma);
if (ret != 0) {
goto cleanup;
}
m = (pthread_mutex_t *)ptr;
if (tdb_robust_mutex_setup_sigchild(tdb_robust_mutex_handler,
&tdb_robust_mutext_old_handler) == false) {
goto cleanup;
}
tdb_robust_mutex_pid = fork();
saved_child_pid = tdb_robust_mutex_pid;
if (tdb_robust_mutex_pid == 0) {
size_t nwritten;
close(pipe_down[1]);
close(pipe_up[0]);
ret = pthread_mutex_lock(m);
nwritten = write(pipe_up[1], &ret, sizeof(ret));
if (nwritten != sizeof(ret)) {
_exit(1);
}
if (ret != 0) {
_exit(1);
}
nread = read(pipe_down[0], &c, 1);
if (nread != 1) {
_exit(1);
}
/* leave locked */
_exit(0);
}
if (tdb_robust_mutex_pid == -1) {
goto cleanup;
}
close(pipe_down[0]);
pipe_down[0] = -1;
close(pipe_up[1]);
pipe_up[1] = -1;
nread = read(pipe_up[0], &ret, sizeof(ret));
if (nread != sizeof(ret)) {
goto cleanup;
}
ret = pthread_mutex_trylock(m);
if (ret != EBUSY) {
if (ret == 0) {
pthread_mutex_unlock(m);
}
goto cleanup;
}
if (write(pipe_down[1], &c, 1) != 1) {
goto cleanup;
}
nread = read(pipe_up[0], &c, 1);
if (nread != 0) {
goto cleanup;
}
tdb_robust_mutex_wait_for_child(&saved_child_pid);
ret = pthread_mutex_trylock(m);
if (ret != EOWNERDEAD) {
if (ret == 0) {
pthread_mutex_unlock(m);
}
goto cleanup;
}
ret = pthread_mutex_consistent(m);
if (ret != 0) {
goto cleanup;
}
ret = pthread_mutex_trylock(m);
if (ret != EDEADLK && ret != EBUSY) {
pthread_mutex_unlock(m);
goto cleanup;
}
ret = pthread_mutex_unlock(m);
if (ret != 0) {
goto cleanup;
}
tdb_mutex_locking_cached = true;
cleanup:
/*
* Note that we don't reset the signal handler we just reset
* tdb_robust_mutex_pid to -1. This is ok as this code path is only
* called once per process.
*
* Leaving our signal handler avoids races with other threads potentialy
* setting up their SIGCHLD handlers.
*
* The worst thing that can happen is that the other newer signal
* handler will get the SIGCHLD signal for our child and/or reap the
* child with a wait() function. tdb_robust_mutex_wait_for_child()
* handles the case where waitpid returns ECHILD.
*/
tdb_robust_mutex_wait_for_child(&saved_child_pid);
if (m != NULL) {
pthread_mutex_destroy(m);
}
if (cleanup_ma) {
pthread_mutexattr_destroy(&ma);
}
if (pipe_down[0] != -1) {
close(pipe_down[0]);
}
if (pipe_down[1] != -1) {
close(pipe_down[1]);
}
if (pipe_up[0] != -1) {
close(pipe_up[0]);
}
if (pipe_up[1] != -1) {
close(pipe_up[1]);
}
if (ptr != NULL) {
munmap(ptr, sizeof(pthread_mutex_t));
}
return tdb_mutex_locking_cached;
}
#else
size_t tdb_mutex_size(struct tdb_context *tdb)
{
return 0;
}
bool tdb_have_mutexes(struct tdb_context *tdb)
{
return false;
}
int tdb_mutex_allrecord_lock(struct tdb_context *tdb, int ltype,
enum tdb_lock_flags flags)
{
tdb->ecode = TDB_ERR_LOCK;
return -1;
}
int tdb_mutex_allrecord_unlock(struct tdb_context *tdb)
{
return -1;
}
int tdb_mutex_allrecord_upgrade(struct tdb_context *tdb)
{
tdb->ecode = TDB_ERR_LOCK;
return -1;
}
void tdb_mutex_allrecord_downgrade(struct tdb_context *tdb)
{
return;
}
int tdb_mutex_mmap(struct tdb_context *tdb)
{
errno = ENOSYS;
return -1;
}
int tdb_mutex_munmap(struct tdb_context *tdb)
{
errno = ENOSYS;
return -1;
}
int tdb_mutex_init(struct tdb_context *tdb)
{
errno = ENOSYS;
return -1;
}
_PUBLIC_ bool tdb_runtime_check_for_robust_mutexes(void)
{
return false;
}
#endif