---
src/lxc/Makefile.am | 3 ++-
src/lxc/attach.c | 2 --
src/lxc/bdev.c | 13 -------------
src/lxc/lxccontainer.c | 4 ----
src/lxc/lxclock.c | 23 ++++++++++++++++++++++-
src/lxc/monitor.c | 1 -
6 files changed, 24 insertions(+), 22 deletions(-)
diff --git a/src/lxc/Makefile.am b/src/lxc/Makefile.am
index 74b38e2..f18d6e1 100644
--- a/src/lxc/Makefile.am
+++ b/src/lxc/Makefile.am
@@ -135,9 +135,10 @@ AM_CFLAGS += -DHAVE_SECCOMP
liblxc_so_SOURCES += seccomp.c
endif
-liblxc_so_CFLAGS = -fPIC -DPIC $(AM_CFLAGS)
+liblxc_so_CFLAGS = -fPIC -DPIC $(AM_CFLAGS) -pthread
liblxc_so_LDFLAGS = \
+ -pthread \
-shared \
-Wl,-soname,liblxc.so.$(firstword $(subst ., ,$(VERSION)))
diff --git a/src/lxc/attach.c b/src/lxc/attach.c
index 6749617..252e172 100644
--- a/src/lxc/attach.c
+++ b/src/lxc/attach.c
@@ -497,7 +497,6 @@ char *lxc_attach_getpwshell(uid_t uid)
NULL
};
- process_unlock(); // we're no longer sharing
close(pipes[0]);
/* we want to capture stdout */
@@ -790,7 +789,6 @@ int lxc_attach(const char* name, const char* lxcpath,
lxc_attach_exec_t exec_fun
return -1;
}
- process_unlock(); // we're no longer sharing
/* first subprocess begins here, we close the socket that is for the
* initial thread
*/
diff --git a/src/lxc/bdev.c b/src/lxc/bdev.c
index b737eff..ec0d0ee 100644
--- a/src/lxc/bdev.c
+++ b/src/lxc/bdev.c
@@ -72,7 +72,6 @@ static int do_rsync(const char *src, const char *dest)
if (pid > 0)
return wait_for_pid(pid);
- process_unlock(); // we're no longer sharing
l = strlen(src) + 2;
s = malloc(l);
if (!s)
@@ -197,7 +196,6 @@ static int do_mkfs(const char *path, const char *fstype)
if (pid > 0)
return wait_for_pid(pid);
- process_unlock(); // we're no longer sharing
// If the file is not a block device, we don't want mkfs to ask
// us about whether to proceed.
close(0);
@@ -282,7 +280,6 @@ static int detect_fs(struct bdev *bdev, char *type, int len)
return ret;
}
- process_unlock(); // we're no longer sharing
if (unshare(CLONE_NEWNS) < 0)
exit(1);
@@ -574,7 +571,6 @@ static int zfs_clone(const char *opath, const char *npath,
const char *oname,
if (!pid) {
char dev[MAXPATHLEN];
- process_unlock(); // we're no longer sharing
ret = snprintf(dev, MAXPATHLEN, "%s/%s", zfsroot,
nname);
if (ret < 0 || ret >= MAXPATHLEN)
exit(1);
@@ -598,7 +594,6 @@ static int zfs_clone(const char *opath, const char *npath,
const char *oname,
if ((pid = fork()) < 0)
return -1;
if (!pid) {
- process_unlock(); // we're no longer sharing
execlp("zfs", "zfs", "destroy", path1, NULL);
exit(1);
}
@@ -609,7 +604,6 @@ static int zfs_clone(const char *opath, const char *npath,
const char *oname,
if ((pid = fork()) < 0)
return -1;
if (!pid) {
- process_unlock(); // we're no longer sharing
execlp("zfs", "zfs", "snapshot", path1, NULL);
exit(1);
}
@@ -620,7 +614,6 @@ static int zfs_clone(const char *opath, const char *npath,
const char *oname,
if ((pid = fork()) < 0)
return -1;
if (!pid) {
- process_unlock(); // we're no longer sharing
execlp("zfs", "zfs", "clone", option, path1, path2,
NULL);
exit(1);
}
@@ -671,7 +664,6 @@ static int zfs_destroy(struct bdev *orig)
if (pid)
return wait_for_pid(pid);
- process_unlock(); // we're no longer sharing
if (!zfs_list_entry(orig->src, output, MAXPATHLEN)) {
ERROR("Error: zfs entry for %s not found", orig->src);
return -1;
@@ -716,7 +708,6 @@ static int zfs_create(struct bdev *bdev, const char *dest,
const char *n,
if (pid)
return wait_for_pid(pid);
- process_unlock(); // we're no longer sharing
char dev[MAXPATHLEN];
ret = snprintf(dev, MAXPATHLEN, "%s/%s", zfsroot, n);
if (ret < 0 || ret >= MAXPATHLEN)
@@ -861,7 +852,6 @@ static int do_lvm_create(const char *path, unsigned long
size, const char *thinp
if (pid > 0)
return wait_for_pid(pid);
- process_unlock(); // we're no longer sharing
// lvcreate default size is in M, not bytes.
ret = snprintf(sz, 24, "%lu", size/1000000);
if (ret < 0 || ret >= 24)
@@ -921,7 +911,6 @@ static int lvm_snapshot(const char *orig, const char *path,
unsigned long size)
if (pid > 0)
return wait_for_pid(pid);
- process_unlock(); // we're no longer sharing
// lvcreate default size is in M, not bytes.
ret = snprintf(sz, 24, "%lu", size/1000000);
if (ret < 0 || ret >= 24)
@@ -1055,7 +1044,6 @@ static int lvm_destroy(struct bdev *orig)
if ((pid = fork()) < 0)
return -1;
if (!pid) {
- process_unlock(); // we're no longer sharing
execlp("lvremove", "lvremove", "-f", orig->src, NULL);
exit(1);
}
@@ -2091,7 +2079,6 @@ struct bdev *bdev_copy(const char *src, const char
*oldname, const char *cname,
return new;
}
- process_unlock(); // we're no longer sharing
if (unshare(CLONE_NEWNS) < 0) {
SYSERROR("unshare CLONE_NEWNS");
exit(1);
diff --git a/src/lxc/lxccontainer.c b/src/lxc/lxccontainer.c
index e1d004f..cf71f28 100644
--- a/src/lxc/lxccontainer.c
+++ b/src/lxc/lxccontainer.c
@@ -599,7 +599,6 @@ static bool lxcapi_start(struct lxc_container *c, int
useinit, char * const argv
if (pid != 0)
return wait_on_daemonized_start(c, pid);
- process_unlock(); // we're no longer sharing
/* second fork to be reparented by init */
pid = fork();
if (pid < 0) {
@@ -837,7 +836,6 @@ static bool create_run_template(struct lxc_container *c,
char *tpath, bool quiet
char **newargv;
struct lxc_conf *conf = c->lxc_conf;
- process_unlock(); // we're no longer sharing
if (quiet) {
close(0);
close(1);
@@ -1234,7 +1232,6 @@ static bool lxcapi_create(struct lxc_container *c, const
char *t,
if (pid == 0) { // child
struct bdev *bdev = NULL;
- process_unlock(); // we're no longer sharing
if (!(bdev = do_bdev_create(c, bdevtype, specs))) {
ERROR("Error creating backing store type %s for %s",
bdevtype ? bdevtype : "(none)", c->name);
@@ -2326,7 +2323,6 @@ static int clone_update_rootfs(struct lxc_container *c0,
if (pid > 0)
return wait_for_pid(pid);
- process_unlock(); // we're no longer sharing
bdev = bdev_init(c->lxc_conf->rootfs.path, c->lxc_conf->rootfs.mount,
NULL);
if (!bdev)
exit(1);
diff --git a/src/lxc/lxclock.c b/src/lxc/lxclock.c
index 28691b0..36c4bd3 100644
--- a/src/lxc/lxclock.c
+++ b/src/lxc/lxclock.c
@@ -87,7 +87,7 @@ void unlock_mutex(pthread_mutex_t *l)
int ret;
if ((ret = pthread_mutex_unlock(l)) != 0) {
- fprintf(stderr, "pthread_mutex_lock returned:%d %s", ret,
strerror(ret));
+ fprintf(stderr, "pthread_mutex_unlock returned:%d %s", ret,
strerror(ret));
dump_stacktrace();
exit(1);
}
@@ -315,6 +315,21 @@ void process_unlock(void)
unlock_mutex(&thread_mutex);
}
+/* One thread can do fork() while another one is holding a mutex.
+ * There is only one thread in child just after the fork(), so noone will ever
release that mutex.
+ * We setup a "child" fork handler to unlock the mutex just after the fork().
+ * For several mutex types, unlocking an unlocked mutex can lead to undefined
behavior.
+ * One way to deal with it is to setup "prepare" fork handler
+ * to lock the mutex before fork() and both "parent" and "child" fork handlers
+ * to unlock the mutex.
+ * This forbids doing fork() while explicitly holding the lock.
+ */
+__attribute__((constructor))
+static void process_lock_setup_atfork(void)
+{
+ pthread_atfork(process_lock, process_unlock, process_unlock);
+}
+
/* Protects static const values inside the lxc_global_config_value funtion */
void static_lock(void)
{
@@ -326,6 +341,12 @@ void static_unlock(void)
unlock_mutex(&static_mutex);
}
+__attribute__((constructor))
+static void static_lock_setup_atfork(void)
+{
+ pthread_atfork(static_lock, static_unlock, static_unlock);
+}
+
int container_mem_lock(struct lxc_container *c)
{
return lxclock(c->privlock, 0);
diff --git a/src/lxc/monitor.c b/src/lxc/monitor.c
index 7e0a713..0b6a065 100644
--- a/src/lxc/monitor.c
+++ b/src/lxc/monitor.c
@@ -300,7 +300,6 @@ int lxc_monitord_spawn(const char *lxcpath)
return 0;
}
- process_unlock(); // we're no longer sharing
if (pipe(pipefd) < 0) {
SYSERROR("failed to create pipe");
exit(EXIT_FAILURE);
--
1.8.4.5
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