diff options
| -rw-r--r-- | ChangeLog | 5 | ||||
| -rw-r--r-- | stdlib/cxa_thread_atexit_impl.c | 19 |
2 files changed, 15 insertions, 9 deletions
@@ -1,3 +1,8 @@ +2015-07-24 Siddhesh Poyarekar <siddhesh@redhat.com> + + * stdlib/cxa_thread_atexit_impl.c: Use the lock name dl_load_lock + instead of just saying load lock in the comments. + 2015-07-23 Roland McGrath <roland@hack.frob.com> * sysdeps/unix/Subdirs: Moved ... diff --git a/stdlib/cxa_thread_atexit_impl.c b/stdlib/cxa_thread_atexit_impl.c index 8e26380..2d5d56a 100644 --- a/stdlib/cxa_thread_atexit_impl.c +++ b/stdlib/cxa_thread_atexit_impl.c @@ -25,14 +25,15 @@ combinations of all three functions are the link map list, a link map for a DSO and the link map member l_tls_dtor_count. - __cxa_thread_atexit_impl acquires the load_lock before accessing any shared - state and hence multiple of its instances can safely execute concurrently. + __cxa_thread_atexit_impl acquires the dl_load_lock before accessing any + shared state and hence multiple of its instances can safely execute + concurrently. - _dl_close_worker acquires the load_lock before accessing any shared state as - well and hence can concurrently execute multiple of its own instances as + _dl_close_worker acquires the dl_load_lock before accessing any shared state + as well and hence can concurrently execute multiple of its own instances as well as those of __cxa_thread_atexit_impl safely. Not all accesses to - l_tls_dtor_count are protected by the load lock, so we need to synchronize - using atomics. + l_tls_dtor_count are protected by the dl_load_lock, so we need to + synchronize using atomics. __call_tls_dtors accesses the l_tls_dtor_count without taking the lock; it decrements the value by one. It does not need the big lock because it does @@ -51,8 +52,8 @@ it is safe to unload the DSO. Hence, to ensure that this does not happen, the following conditions must be met: - 1. In _dl_close_worker, the l_tls_dtor_count load happens before the DSO - is unload and its link map is freed + 1. In _dl_close_worker, the l_tls_dtor_count load happens before the DSO is + unloaded and its link map is freed 2. The link map dereference in __call_tls_dtors happens before the l_tls_dtor_count dereference. @@ -122,7 +123,7 @@ __cxa_thread_atexit_impl (dtor_func func, void *obj, void *dso_symbol) /* This increment may only be concurrently observed either by the decrement in __call_tls_dtors since the other l_tls_dtor_count access in - _dl_close_worker is protected by the load lock. The execution in + _dl_close_worker is protected by the dl_load_lock. The execution in __call_tls_dtors does not really depend on this value beyond the fact that it should be atomic, so Relaxed MO should be sufficient. */ atomic_fetch_add_relaxed (&lm_cache->l_tls_dtor_count, 1); |