diff options
Diffstat (limited to 'elf/dl-tls.c')
| -rw-r--r-- | elf/dl-tls.c | 31 |
1 files changed, 23 insertions, 8 deletions
diff --git a/elf/dl-tls.c b/elf/dl-tls.c index 94f3cdbae0..dc69cd984e 100644 --- a/elf/dl-tls.c +++ b/elf/dl-tls.c @@ -179,7 +179,9 @@ _dl_next_tls_modid (void) /* No gaps, allocate a new entry. */ nogaps: - result = ++GL(dl_tls_max_dtv_idx); + result = GL(dl_tls_max_dtv_idx) + 1; + /* Can be read concurrently. */ + atomic_store_relaxed (&GL(dl_tls_max_dtv_idx), result); } return result; @@ -363,10 +365,12 @@ allocate_dtv (void *result) dtv_t *dtv; size_t dtv_length; + /* Relaxed MO, because the dtv size is later rechecked, not relied on. */ + size_t max_modid = atomic_load_relaxed (&GL(dl_tls_max_dtv_idx)); /* We allocate a few more elements in the dtv than are needed for the initial set of modules. This should avoid in most cases expansions of the dtv. */ - dtv_length = GL(dl_tls_max_dtv_idx) + DTV_SURPLUS; + dtv_length = max_modid + DTV_SURPLUS; dtv = calloc (dtv_length + 2, sizeof (dtv_t)); if (dtv != NULL) { @@ -771,7 +775,7 @@ _dl_update_slotinfo (unsigned long int req_modid) if (modid > max_modid) break; - size_t gen = listp->slotinfo[cnt].gen; + size_t gen = atomic_load_relaxed (&listp->slotinfo[cnt].gen); if (gen > new_gen) /* Not relevant. */ @@ -783,7 +787,8 @@ _dl_update_slotinfo (unsigned long int req_modid) continue; /* If there is no map this means the entry is empty. */ - struct link_map *map = listp->slotinfo[cnt].map; + struct link_map *map + = atomic_load_relaxed (&listp->slotinfo[cnt].map); /* Check whether the current dtv array is large enough. */ if (dtv[-1].counter < modid) { @@ -927,7 +932,12 @@ __tls_get_addr (GET_ADDR_ARGS) { dtv_t *dtv = THREAD_DTV (); - if (__glibc_unlikely (dtv[0].counter != GL(dl_tls_generation))) + /* Update is needed if dtv[0].counter < the generation of the accessed + module. The global generation counter is used here as it is easier + to check. Synchronization for the relaxed MO access is guaranteed + by user code, see CONCURRENCY NOTES in _dl_update_slotinfo. */ + size_t gen = atomic_load_relaxed (&GL(dl_tls_generation)); + if (__glibc_unlikely (dtv[0].counter != gen)) return update_get_addr (GET_ADDR_PARAM); void *p = dtv[GET_ADDR_MODULE].pointer.val; @@ -950,7 +960,10 @@ _dl_tls_get_addr_soft (struct link_map *l) return NULL; dtv_t *dtv = THREAD_DTV (); - if (__glibc_unlikely (dtv[0].counter != GL(dl_tls_generation))) + /* This may be called without holding the GL(dl_load_lock). Reading + arbitrary gen value is fine since this is best effort code. */ + size_t gen = atomic_load_relaxed (&GL(dl_tls_generation)); + if (__glibc_unlikely (dtv[0].counter != gen)) { /* This thread's DTV is not completely current, but it might already cover this module. */ @@ -1036,8 +1049,10 @@ cannot create TLS data structures")); /* Add the information into the slotinfo data structure. */ if (do_add) { - listp->slotinfo[idx].map = l; - listp->slotinfo[idx].gen = GL(dl_tls_generation) + 1; + /* Can be read concurrently. See _dl_update_slotinfo. */ + atomic_store_relaxed (&listp->slotinfo[idx].map, l); + atomic_store_relaxed (&listp->slotinfo[idx].gen, + GL(dl_tls_generation) + 1); } } |