lib/glibc
1
0
Fork 0
mirror of https://sourceware.org/git/glibc.git synced 2025-08-08 17:42:12 +03:00
Code Activity

Async-signal safe TLS.

Browse Source 
ChangeLog:

2014-01-03  Andrew Hunter  <ahh@google.com>

	* elf/dl-open.c (): New comment.
	* elf/dl-reloc.c (_dl_try_allocate_static_tls): Use
	atomic_compare_and_exchange_bool_acq
	(_dl_allocate_static_tls): Block signals.
	* elf/dl-tls.c (allocate_and_init): Return void.
	(_dl_update_slotinfo): Block signals, use atomic update.

nptl/ChangeLog:

2014-01-03  Andrew Hunter  <ahh@google.com>

	* nptl/Makefile (tst-tls7): New test.
	* nptl/tst-tls7.c: New file.
	* nptl/tst-tls7mod.c: New file.
	* nptl/allocatestack.c (init_one_static_tls): Use atomic barrier.
This commit is contained in:
Andrew Hunter
2014-01-03 11:22:26 -08:00
committed by Paul Pluzhnikov
parent 7dd009d865
commit 7f507ee17a
9 changed files with 313 additions and 46 deletions
Download Patch File Download Diff File Expand all files Collapse all files

48
elf/dl-reloc.c
View File

@@ -16,8 +16,10 @@
License along with the GNU C Library; if not, see
<http://www.gnu.org/licenses/>. */
#include <atomic.h>
#include <errno.h>
#include <libintl.h>
#include <signal.h>
#include <stdlib.h>
#include <unistd.h>
#include <ldsodefs.h>
@@ -70,8 +72,6 @@ _dl_try_allocate_static_tls (struct link_map *map)
size_t offset = GL(dl_tls_static_used) + (freebytes - n * map->l_tls_align
- map->l_tls_firstbyte_offset);
map->l_tls_offset = GL(dl_tls_static_used) = offset;
#elif TLS_DTV_AT_TP
/* dl_tls_static_used includes the TCB at the beginning. */
size_t offset = (((GL(dl_tls_static_used)
@@ -83,7 +83,36 @@ _dl_try_allocate_static_tls (struct link_map *map)
if (used > GL(dl_tls_static_size))
goto fail;
map->l_tls_offset = offset;
#else
# error "Either TLS_TCB_AT_TP or TLS_DTV_AT_TP must be defined"
#endif
/* We've computed the new value we want, now try to install it. */
ptrdiff_t val;
if ((val = map->l_tls_offset) == NO_TLS_OFFSET)
{
/* l_tls_offset starts out at NO_TLS_OFFSET, and all attempts to
change it go from NO_TLS_OFFSET to some other value. We use
compare_and_exchange to ensure only one attempt succeeds. We
don't actually need any memory ordering here, but _acq is the
weakest available. */
(void ) atomic_compare_and_exchange_bool_acq (&map->l_tls_offset,
offset,
NO_TLS_OFFSET);
val = map->l_tls_offset;
assert (val != NO_TLS_OFFSET);
}
if (val != offset)
{
/* We'd like to set a static offset for this section, but another
thread has already used a dynamic TLS block for it. Since we can
only use static offsets if everyone does (and it's not practical
to move that thread's dynamic block), we have to fail. */
goto fail;
}
/* We installed the value; now update the globals. */
#if TLS_TCB_AT_TP
GL(dl_tls_static_used) = offset;
#elif TLS_DTV_AT_TP
map->l_tls_firstbyte_offset = GL(dl_tls_static_used);
GL(dl_tls_static_used) = used;
#else
@@ -114,8 +143,17 @@ void
internal_function __attribute_noinline__
_dl_allocate_static_tls (struct link_map *map)
{
if (map->l_tls_offset == FORCED_DYNAMIC_TLS_OFFSET
|| _dl_try_allocate_static_tls (map))
/* We wrap this in a signal mask because it has to iterate all threads
(including this one) and update this map's TLS entry. A signal handler
accessing TLS would try to do the same update and break. */
sigset_t old;
_dl_mask_all_signals (&old);
int err = -1;
if (map->l_tls_offset != FORCED_DYNAMIC_TLS_OFFSET)
err = _dl_try_allocate_static_tls (map);
_dl_unmask_signals (&old);
if (err != 0)
{
_dl_signal_error (0, map->l_name, NULL, N_("\
cannot allocate memory in static TLS block"));