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Commit 1e609623 by Serge Hallyn Committed by Stéphane Graber
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cgmanager: avoid stray dbus connections

There are two parts to this fix. First, create a private DBusConnection manually, instead of using nih_dbus_connect. The latter always creates a shared connection, which cannot be closed. Note: creating an actual shared connection, mutexing it among all threads, and creating per-thread proxies would be an alternative - however we don't want long-lived connections as they tend not to be reliable (especially if cgmanager restarts). Second, use pthread_setspecific to create per-thread keys which can be associated with destructors. Specify a destructor which closes the dbus connection. If a thread dies while holding cgmanager, the connection will be closed. Otherwise, we close the connection and unset the key. Signed-off-by: 's avatarSerge Hallyn <serge.hallyn@ubuntu.com> Acked-by: 's avatarStéphane Graber <stgraber@ubuntu.com>
parent 184072bc
Showing with 47 additions and 2 deletions
src/lxc/cgmanager.c
...@@ -70,10 +70,42 @@ struct cgm_data { ...@@ -70,10 +70,42 @@ struct cgm_data {
static __thread NihDBusProxy *cgroup_manager = NULL; static __thread NihDBusProxy *cgroup_manager = NULL;
static __thread DBusConnection *connection = NULL; static __thread DBusConnection *connection = NULL;
static __thread bool cgm_keep_connection = false; static __thread bool cgm_keep_connection = false;
struct cgm_key_t {
DBusConnection *connection;
NihDBusProxy *cgmanager;
} cgm_key;
void destructor(void *arg) {
struct cgm_key_t *cgm_key = arg;
nih_free(cgm_key->cgmanager);
dbus_connection_flush(cgm_key->connection);
dbus_connection_close(cgm_key->connection);
dbus_connection_unref(cgm_key->connection);
}
static pthread_key_t key;
static void make_key() {
pthread_key_create(&key, destructor);
}
static void init_cgm_destructor(DBusConnection *c, NihDBusProxy *cgm)
{
static pthread_once_t key_once = PTHREAD_ONCE_INIT;
pthread_once(&key_once, make_key);
cgm_key.connection = c;
cgm_key.cgmanager = cgm;
if (!cgm)
pthread_setspecific(key, NULL);
else if (pthread_getspecific(key) == NULL)
pthread_setspecific(key, &cgm_key);
}
#else #else
static NihDBusProxy *cgroup_manager = NULL; static NihDBusProxy *cgroup_manager = NULL;
static DBusConnection *connection = NULL; static DBusConnection *connection = NULL;
static bool cgm_keep_connection = false; static bool cgm_keep_connection = false;
static inline void init_cgm_destructor(DBusConnection *c, NihDBusProxy *cgm) { }
#endif #endif
static struct cgroup_ops cgmanager_ops; static struct cgroup_ops cgmanager_ops;
...@@ -87,9 +119,13 @@ static void cgm_dbus_disconnect(void) ...@@ -87,9 +119,13 @@ static void cgm_dbus_disconnect(void)
if (cgroup_manager) if (cgroup_manager)
nih_free(cgroup_manager); nih_free(cgroup_manager);
cgroup_manager = NULL; cgroup_manager = NULL;
if (connection) if (connection) {
dbus_connection_flush(connection);
dbus_connection_close(connection);
dbus_connection_unref(connection); dbus_connection_unref(connection);
}
connection = NULL; connection = NULL;
init_cgm_destructor(NULL, NULL);
} }
#define CGMANAGER_DBUS_SOCK "unix:path=/sys/fs/cgroup/cgmanager/sock" #define CGMANAGER_DBUS_SOCK "unix:path=/sys/fs/cgroup/cgmanager/sock"
...@@ -105,14 +141,22 @@ static bool do_cgm_dbus_connect(void) ...@@ -105,14 +141,22 @@ static bool do_cgm_dbus_connect(void)
dbus_error_init(&dbus_error); dbus_error_init(&dbus_error);
connection = nih_dbus_connect(CGMANAGER_DBUS_SOCK, NULL); connection = dbus_connection_open_private(CGMANAGER_DBUS_SOCK, &dbus_error);
if (!connection) { if (!connection) {
ERROR("Failed opening dbus connection: %s: %s",
dbus_error.name, dbus_error.message);
dbus_error_free(&dbus_error);
return false;
}
if (nih_dbus_setup(connection, NULL) < 0) {
NihError *nerr; NihError *nerr;
nerr = nih_error_get(); nerr = nih_error_get();
DEBUG("Unable to open cgmanager connection at %s: %s", CGMANAGER_DBUS_SOCK, DEBUG("Unable to open cgmanager connection at %s: %s", CGMANAGER_DBUS_SOCK,
nerr->message); nerr->message);
nih_free(nerr); nih_free(nerr);
dbus_error_free(&dbus_error); dbus_error_free(&dbus_error);
dbus_connection_unref(connection);
connection = NULL;
return false; return false;
} }
dbus_connection_set_exit_on_disconnect(connection, FALSE); dbus_connection_set_exit_on_disconnect(connection, FALSE);
...@@ -138,6 +182,7 @@ static bool do_cgm_dbus_connect(void) ...@@ -138,6 +182,7 @@ static bool do_cgm_dbus_connect(void)
cgm_dbus_disconnect(); cgm_dbus_disconnect();
return false; return false;
} }
init_cgm_destructor(connection, cgroup_manager);
return true; return true;
} }
......
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