previously, going way back, there was simply no synchronization here.
a call to exit concurrent with ctor execution from dlopen could cause
a dtor to execute concurrently with its corresponding ctor, or could
cause dtors for newly-constructed libraries to be skipped.
introduce a shutting_down state that blocks further ctor execution,
producing the quiescence the dtor execution loop needs to ensure any
kind of consistency, and that blocks further calls to dlopen so that a
call into dlopen from a dtor cannot deadlock.
better approaches to some of this may be possible, but the changes
here at least make things safe.
static int ldd_mode;
static int ldso_fail;
static int noload;
static int ldd_mode;
static int ldso_fail;
static int noload;
+static int shutting_down;
static jmp_buf *rtld_fail;
static pthread_rwlock_t lock;
static struct debug debug;
static jmp_buf *rtld_fail;
static pthread_rwlock_t lock;
static struct debug debug;
{
struct dso *p;
size_t dyn[DYN_CNT];
{
struct dso *p;
size_t dyn[DYN_CNT];
+ int self = __pthread_self()->tid;
+
+ /* Take both locks before setting shutting_down, so that
+ * either lock is sufficient to read its value. The lock
+ * order matches that in dlopen to avoid deadlock. */
+ pthread_rwlock_wrlock(&lock);
+ pthread_mutex_lock(&init_fini_lock);
+ shutting_down = 1;
+ pthread_rwlock_unlock(&lock);
for (p=fini_head; p; p=p->fini_next) {
for (p=fini_head; p; p=p->fini_next) {
+ while (p->ctor_visitor && p->ctor_visitor!=self)
+ pthread_cond_wait(&ctor_cond, &init_fini_lock);
if (!p->constructed) continue;
decode_vec(p->dynv, dyn, DYN_CNT);
if (dyn[0] & (1<<DT_FINI_ARRAY)) {
if (!p->constructed) continue;
decode_vec(p->dynv, dyn, DYN_CNT);
if (dyn[0] & (1<<DT_FINI_ARRAY)) {
pthread_mutex_lock(&init_fini_lock);
for (i=0; (p=queue[i]); i++) {
pthread_mutex_lock(&init_fini_lock);
for (i=0; (p=queue[i]); i++) {
- while (p->ctor_visitor && p->ctor_visitor!=self)
+ while ((p->ctor_visitor && p->ctor_visitor!=self) || shutting_down)
pthread_cond_wait(&ctor_cond, &init_fini_lock);
if (p->ctor_visitor || p->constructed)
continue;
pthread_cond_wait(&ctor_cond, &init_fini_lock);
if (p->ctor_visitor || p->constructed)
continue;
+ if (shutting_down) {
+ error("Cannot dlopen while program is exiting.");
+ goto end;
+ }
orig_tls_tail = tls_tail;
orig_tls_cnt = tls_cnt;
orig_tls_offset = tls_offset;
orig_tls_tail = tls_tail;
orig_tls_cnt = tls_cnt;
orig_tls_offset = tls_offset;