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| author | Szabolcs Nagy <szabolcs.nagy@arm.com> | 2021-09-15 15:16:19 +0100 |
|---|---|---|
| committer | Szabolcs Nagy <szabolcs.nagy@arm.com> | 2021-10-04 15:07:05 +0100 |
| commit | 83b5323261bb72313bffcf37476c1b8f0847c736 (patch) | |
| tree | 2359c0540ec0009d3b010f35fd4cec6a2ca89253 /elf/dl-support.c | |
| parent | 958309cba24caf58ea5e118b20eccadbb3638f2d (diff) | |
| download | glibc-83b5323261bb72313bffcf37476c1b8f0847c736.tar.gz glibc-83b5323261bb72313bffcf37476c1b8f0847c736.tar.xz glibc-83b5323261bb72313bffcf37476c1b8f0847c736.zip | |
elf: Avoid deadlock between pthread_create and ctors [BZ #28357]
The fix for bug 19329 caused a regression such that pthread_create can deadlock when concurrent ctors from dlopen are waiting for it to finish. Use a new GL(dl_load_tls_lock) in pthread_create that is not taken around ctors in dlopen. The new lock is also used in __tls_get_addr instead of GL(dl_load_lock). The new lock is held in _dl_open_worker and _dl_close_worker around most of the logic before/after the init/fini routines. When init/fini routines are running then TLS is in a consistent, usable state. In _dl_open_worker the new lock requires catching and reraising dlopen failures that happen in the critical section. The new lock is reinitialized in a fork child, to keep the existing behaviour and it is kept recursive in case malloc interposition or TLS access from signal handlers can retake it. It is not obvious if this is necessary or helps, but avoids changing the preexisting behaviour. The new lock may be more appropriate for dl_iterate_phdr too than GL(dl_load_write_lock), since TLS state of an incompletely loaded module may be accessed. If the new lock can replace the old one, that can be a separate change. Fixes bug 28357. Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Diffstat (limited to 'elf/dl-support.c')
| -rw-r--r-- | elf/dl-support.c | 7 |
1 files changed, 7 insertions, 0 deletions
diff --git a/elf/dl-support.c b/elf/dl-support.c index 02e2ed72f5..d99c1f1d62 100644 --- a/elf/dl-support.c +++ b/elf/dl-support.c @@ -228,6 +228,13 @@ __rtld_lock_define_initialized_recursive (, _dl_load_lock) list of loaded objects while an object is added to or removed from that list. */ __rtld_lock_define_initialized_recursive (, _dl_load_write_lock) + /* This lock protects global and module specific TLS related data. + E.g. it is held in dlopen and dlclose when GL(dl_tls_generation), + GL(dl_tls_max_dtv_idx) or GL(dl_tls_dtv_slotinfo_list) are + accessed and when TLS related relocations are processed for a + module. It was introduced to keep pthread_create accessing TLS + state that is being set up. */ +__rtld_lock_define_initialized_recursive (, _dl_load_tls_lock) #ifdef HAVE_AUX_VECTOR |