[COMMITTED] Bug 20915: Do not initialize DTV of other threads.

[Carlos O'Donell <carlos at redhat dot com>]

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.