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[COMMITTED] Bug 20915: Do not initialize DTV of other threads.
- From: Carlos O'Donell <carlos at redhat dot com>
- To: GNU C Library <libc-alpha at sourceware dot org>, Siddhesh Poyarekar <siddhesh at gotplt dot org>
- Cc: Alexandre Oliva <aoliva at redhat dot com>, Florian Weimer <fweimer at redhat dot com>
- Date: Fri, 3 Feb 2017 21:34:46 -0500
- Subject: [COMMITTED] Bug 20915: Do not initialize DTV of other threads.
- Authentication-results: sourceware.org; auth=none
In _dl_nothread_init_static_tls() and init_one_static_tls() we must not
touch the DTV of other threads since we do not have ownership of them.
The DTV need not be initialized at this point anyway since only LD/GD
accesses will use them. If LD/GD accesses occur they will take care to
initialize their own thread's DTV.
Concurrency comments were removed from the patch since they need to be
reworked along with a full description of DTV ownership and when it is
or is not safe to modify these structures.
Alexandre Oliva's original patch and discussion:
https://sourceware.org/ml/libc-alpha/2016-09/msg00512.html
I have verified this fix on aarch64, ppc64, ppc64le, and x86_64 with
no regressions.
The changes fix tst-tls-manydynamic on aarch64, ppc64, ppc64le.
I have commited the following patch.
2017-02-03 Alexandre Oliva <aoliva@redhat.com>
Florian Weimer <fweimer@redhat.com>
Carlos O'Donell <carlos@redhat.com>
[BZ #20915]
* elf/dl-reloc.c (_dl_nothread_init_static_tls):
Do not initialize DTV.
* nptl/allocatestack.c (init_one_static_tls): Likewise.
diff --git a/elf/dl-reloc.c b/elf/dl-reloc.c
index 52311f0..4ac558d 100644
--- a/elf/dl-reloc.c
+++ b/elf/dl-reloc.c
@@ -137,12 +137,6 @@ _dl_nothread_init_static_tls (struct link_map *map)
# error "Either TLS_TCB_AT_TP or TLS_DTV_AT_TP must be defined"
#endif
- /* Fill in the DTV slot so that a later LD/GD access will find it. */
- dtv_t *dtv = THREAD_DTV ();
- assert (map->l_tls_modid <= dtv[-1].counter);
- dtv[map->l_tls_modid].pointer.to_free = NULL;
- dtv[map->l_tls_modid].pointer.val = dest;
-
/* Initialize the memory. */
memset (__mempcpy (dest, map->l_tls_initimage, map->l_tls_initimage_size),
'\0', map->l_tls_blocksize - map->l_tls_initimage_size);
diff --git a/nptl/allocatestack.c b/nptl/allocatestack.c
index 6402ea4..8a228ab 100644
--- a/nptl/allocatestack.c
+++ b/nptl/allocatestack.c
@@ -1191,11 +1191,6 @@ init_one_static_tls (struct pthread *curp, struct link_map *map)
# error "Either TLS_TCB_AT_TP or TLS_DTV_AT_TP must be defined"
# endif
- /* Fill in the DTV slot so that a later LD/GD access will find it. */
- dtv_t *dtv = GET_DTV (TLS_TPADJ (curp));
- dtv[map->l_tls_modid].pointer.to_free = NULL;
- dtv[map->l_tls_modid].pointer.val = dest;
-
/* Initialize the memory. */
memset (__mempcpy (dest, map->l_tls_initimage, map->l_tls_initimage_size),
'\0', map->l_tls_blocksize - map->l_tls_initimage_size);
---
--
Cheers,
Carlos.