Revert "Async-signal safe TLS."

This reverts commit 7f507ee17aee720fa423fa38502bc3caa0dd03d7.

Conflicts:
	ChangeLog
	nptl/tst-tls7.c
	nptl/tst-tls7mod.c

3 files changed, 39 insertions, 114 deletions

diff --git a/elf/dl-open.c b/elf/dl-open.c
index ea222d0..a9ca6b3 100644
--- a/elf/dl-open.c
+++ b/elf/dl-open.c
@@ -548,10 +548,7 @@ cannot load any more object with static TLS"));
 	     generation of the DSO we are allocating data for.  */
 	  _dl_update_slotinfo (imap->l_tls_modid);
 #endif
-	  /* We do this iteration under a signal mask in dl-reloc; why not
-	     here?  Because these symbols are new and dlopen hasn't
-	     returned yet.  So we can't possibly be racing with a TLS
-	     access to them from another thread.  */
+
 	  GL(dl_init_static_tls) (imap);
 	  assert (imap->l_need_tls_init == 0);
 	}
diff --git a/elf/dl-reloc.c b/elf/dl-reloc.c
index 81ee47e..1f66fcc 100644
--- a/elf/dl-reloc.c
+++ b/elf/dl-reloc.c
@@ -16,10 +16,8 @@
    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>
@@ -72,6 +70,8 @@ _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)
@@ -83,36 +83,7 @@ _dl_try_allocate_static_tls (struct link_map *map)
   if (used > GL(dl_tls_static_size))
     goto fail;
 
-#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_offset = offset;
   map->l_tls_firstbyte_offset = GL(dl_tls_static_used);
   GL(dl_tls_static_used) = used;
 #else
@@ -143,17 +114,8 @@ void
 internal_function __attribute_noinline__
 _dl_allocate_static_tls (struct link_map *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)
+  if (map->l_tls_offset == FORCED_DYNAMIC_TLS_OFFSET
+      || _dl_try_allocate_static_tls (map))
     {
       _dl_signal_error (0, map->l_name, NULL, N_("\
 cannot allocate memory in static TLS block"));
diff --git a/elf/dl-tls.c b/elf/dl-tls.c
index 50ec876..c1802e7 100644
--- a/elf/dl-tls.c
+++ b/elf/dl-tls.c
@@ -17,7 +17,6 @@
    <http://www.gnu.org/licenses/>.  */
 
 #include <assert.h>
-#include <atomic.h>
 #include <errno.h>
 #include <libintl.h>
 #include <signal.h>
@@ -534,21 +533,19 @@ rtld_hidden_def (_dl_deallocate_tls)
 # endif
 
 
-static void
-allocate_and_init (dtv_t *dtv, struct link_map *map)
+static void *
+allocate_and_init (struct link_map *map)
 {
   void *newp;
   newp = __signal_safe_memalign (map->l_tls_align, map->l_tls_blocksize);
   if (newp == NULL)
     oom ();
 
-  /* Initialize the memory. Since this is our thread's space, we are
-     under a signal mask, and no one has touched this section before,
-     we can safely just overwrite whatever's there.  */
+  /* Initialize the memory.  */
   memset (__mempcpy (newp, map->l_tls_initimage, map->l_tls_initimage_size),
 	  '\0', map->l_tls_blocksize - map->l_tls_initimage_size);
 
-  dtv->pointer.val = newp;
+  return newp;
 }
 
 
@@ -590,15 +587,7 @@ _dl_update_slotinfo (unsigned long int req_modid)
 	 the entry we need.  */
       size_t new_gen = listp->slotinfo[idx].gen;
       size_t total = 0;
-      sigset_t old;
-
-      _dl_mask_all_signals (&old);
-      /* We use the signal mask as a lock against reentrancy here.
-         Check that a signal taken before the lock didn't already
-         update us.  */
-      dtv = THREAD_DTV ();
-      if (dtv[0].counter >= listp->slotinfo[idx].gen)
-        goto out;
+
       /* We have to look through the entire dtv slotinfo list.  */
       listp =  GL(dl_tls_dtv_slotinfo_list);
       do
@@ -710,8 +699,6 @@ _dl_update_slotinfo (unsigned long int req_modid)
 
       /* This will be the new maximum generation counter.  */
       dtv[0].counter = new_gen;
-   out:
-      _dl_unmask_signals (&old);
     }
 
   return the_map;
@@ -737,60 +724,39 @@ tls_get_addr_tail (GET_ADDR_ARGS, dtv_t *dtv, struct link_map *the_map)
 
       the_map = listp->slotinfo[idx].map;
     }
-  sigset_t old;
-  _dl_mask_all_signals (&old);
-
-  /* As with update_slotinfo, we use the sigmask as a check against
-     reentrancy.  */
-  if (dtv[GET_ADDR_MODULE].pointer.val != TLS_DTV_UNALLOCATED)
-    goto out;
-
-  /* Synchronize against a parallel dlopen() forcing this variable
-     into static storage.  If that happens, we have to be more careful
-     about initializing the area, as that dlopen() will be iterating
-     the threads to do so itself.  */
-  ptrdiff_t offset;
-  if ((offset = the_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 (&the_map->l_tls_offset,
-						   FORCED_DYNAMIC_TLS_OFFSET,
-						   NO_TLS_OFFSET);
-      offset = the_map->l_tls_offset;
-      assert (offset != NO_TLS_OFFSET);
-    }
-  if (offset == FORCED_DYNAMIC_TLS_OFFSET)
-    {
-      allocate_and_init (&dtv[GET_ADDR_MODULE], the_map);
-    }
-  else
+
+ again:
+  /* Make sure that, if a dlopen running in parallel forces the
+     variable into static storage, we'll wait until the address in the
+     static TLS block is set up, and use that.  If we're undecided
+     yet, make sure we make the decision holding the lock as well.  */
+  if (__builtin_expect (the_map->l_tls_offset
+			!= FORCED_DYNAMIC_TLS_OFFSET, 0))
     {
-      void **pp = &dtv[GET_ADDR_MODULE].pointer.val;
-      while (atomic_forced_read (*pp) == TLS_DTV_UNALLOCATED)
+      __rtld_lock_lock_recursive (GL(dl_load_lock));
+      if (__builtin_expect (the_map->l_tls_offset == NO_TLS_OFFSET, 1))
 	{
-	  /* for lack of a better (safe) thing to do, just spin.
-	    Someone else (not us; it's done under a signal mask) set
-	    this map to a static TLS offset, and they'll iterate all
-	    threads to initialize it.  They'll eventually write
-	    to pointer.val, at which point we know they've fully
-	    completed initialization.  */
-	  atomic_delay ();
+	  the_map->l_tls_offset = FORCED_DYNAMIC_TLS_OFFSET;
+	  __rtld_lock_unlock_recursive (GL(dl_load_lock));
+	}
+      else
+	{
+	  __rtld_lock_unlock_recursive (GL(dl_load_lock));
+	  if (__builtin_expect (the_map->l_tls_offset
+				!= FORCED_DYNAMIC_TLS_OFFSET, 1))
+	    {
+	      void *p = dtv[GET_ADDR_MODULE].pointer.val;
+	      if (__builtin_expect (p == TLS_DTV_UNALLOCATED, 0))
+		goto again;
+
+	      return (char *) p + GET_ADDR_OFFSET;
+	    }
 	}
-      /* Make sure we've picked up their initialization of the actual
-	 block; this pairs against the write barrier in
-	 init_one_static_tls, guaranteeing that we see their write of
-	 the tls_initimage into the static region.  */
-      atomic_read_barrier ();
     }
-out:
-  assert (dtv[GET_ADDR_MODULE].pointer.val != TLS_DTV_UNALLOCATED);
-  _dl_unmask_signals (&old);
+  void *p = dtv[GET_ADDR_MODULE].pointer.val = allocate_and_init (the_map);
+  dtv[GET_ADDR_MODULE].pointer.is_static = false;
 
-  return (char *) dtv[GET_ADDR_MODULE].pointer.val + GET_ADDR_OFFSET;
+  return (char *) p + GET_ADDR_OFFSET;
 }