Revert "Async-signal safe TLS."

This reverts commit 7f507ee17a.

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

ChangeLog

@@ -561,15 +561,6 @@
 	* sysdeps/powerpc/powerpc64/multiarch/strnlen-power7.S: Likewise.
 	* sysdeps/powerpc/powerpc64/multiarch/wcscpy.c: Likewise.
 
-2014-01-03  Andrew Hunter  <ahh@google.com>
-
-	* elf/dl-open.c (dl_open_worker): 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.
-
 2014-01-03  Joseph Myers  <joseph@codesourcery.com>
 
 	* sysdeps/powerpc/nofpu/libm-test-ulps: Regenerated.

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);
 	}

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
+  map->l_tls_offset = offset;
-# 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
@@ -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
+  if (map->l_tls_offset == FORCED_DYNAMIC_TLS_OFFSET
-     (including this one) and update this map's TLS entry. A signal handler
+      || _dl_try_allocate_static_tls (map))
-     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"));

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
+static void *
-allocate_and_init (dtv_t *dtv, struct link_map *map)
+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
+  /* Initialize the memory.  */
-     under a signal mask, and no one has touched this section before,
-     we can safely just overwrite whatever's there.  */
   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
+ again:
-     reentrancy.  */
+  /* Make sure that, if a dlopen running in parallel forces the
-  if (dtv[GET_ADDR_MODULE].pointer.val != TLS_DTV_UNALLOCATED)
+     variable into static storage, we'll wait until the address in the
-    goto out;
+     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.  */
-  /* Synchronize against a parallel dlopen() forcing this variable
+  if (__builtin_expect (the_map->l_tls_offset
-     into static storage.  If that happens, we have to be more careful
+			!= FORCED_DYNAMIC_TLS_OFFSET, 0))
-     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
+      __rtld_lock_lock_recursive (GL(dl_load_lock));
-	 change it go from NO_TLS_OFFSET to some other value.  We use
+      if (__builtin_expect (the_map->l_tls_offset == NO_TLS_OFFSET, 1))
-	 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);
+	  the_map->l_tls_offset = FORCED_DYNAMIC_TLS_OFFSET;
+	  __rtld_lock_unlock_recursive (GL(dl_load_lock));
 	}
       else
 	{
-      void **pp = &dtv[GET_ADDR_MODULE].pointer.val;
+	  __rtld_lock_unlock_recursive (GL(dl_load_lock));
-      while (atomic_forced_read (*pp) == TLS_DTV_UNALLOCATED)
+	  if (__builtin_expect (the_map->l_tls_offset
+				!= FORCED_DYNAMIC_TLS_OFFSET, 1))
 	    {
-	  /* for lack of a better (safe) thing to do, just spin.
+	      void *p = dtv[GET_ADDR_MODULE].pointer.val;
-	    Someone else (not us; it's done under a signal mask) set
+	      if (__builtin_expect (p == TLS_DTV_UNALLOCATED, 0))
-	    this map to a static TLS offset, and they'll iterate all
+		goto again;
-	    threads to initialize it.  They'll eventually write
-	    to pointer.val, at which point we know they've fully
-	    completed initialization.  */
-	  atomic_delay ();
-	}
-      /* 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);
 
-  return (char *) dtv[GET_ADDR_MODULE].pointer.val + GET_ADDR_OFFSET;
+	      return (char *) p + GET_ADDR_OFFSET;
+	    }
+	}
+    }
+  void *p = dtv[GET_ADDR_MODULE].pointer.val = allocate_and_init (the_map);
+  dtv[GET_ADDR_MODULE].pointer.is_static = false;
+
+  return (char *) p + GET_ADDR_OFFSET;
 }
 
 

nptl/ChangeLog

@@ -19,14 +19,7 @@
 	(do_test): Call it.
 	* tst-tls7mod.c (action): Move sem_post to caller.
 
-2014-01-03  Andrew Hunter  <ahh@google.com>
+2011-12-12  Adhemerval Zanella  <azanella@linux.vnet.ibm.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.
-
-2013-12-12  Adhemerval Zanella  <azanella@linux.vnet.ibm.com>
 
 	* sysdeps/powerpc/tls.h (struct tcbhead_t): Add DSO and TAR fields.
 	* nptl/sysdeps/powerpc/tcb-offsets.sym: Likewise.

nptl/Makefile

@@ -293,7 +293,7 @@ tests += tst-cancelx2 tst-cancelx3 tst-cancelx4 tst-cancelx5 \
 	 tst-oncex3 tst-oncex4
 endif
 ifeq ($(build-shared),yes)
-tests += tst-atfork2 tst-tls3 tst-tls4 tst-tls5 tst-tls7 tst-_res1 tst-fini1 \
+tests += tst-atfork2 tst-tls3 tst-tls4 tst-tls5 tst-_res1 tst-fini1 \
 	 tst-stackguard1
 tests-nolibpthread += tst-fini1
 ifeq ($(have-z-execstack),yes)
@@ -304,8 +304,7 @@ endif
 modules-names = tst-atfork2mod tst-tls3mod tst-tls4moda tst-tls4modb \
 		tst-tls5mod tst-tls5moda tst-tls5modb tst-tls5modc \
 		tst-tls5modd tst-tls5mode tst-tls5modf \
-		tst-_res1mod1 tst-_res1mod2 tst-execstack-mod tst-fini1mod \
+		tst-_res1mod1 tst-_res1mod2 tst-execstack-mod tst-fini1mod
-		tst-tls7mod
 extra-test-objs += $(addsuffix .os,$(strip $(modules-names))) tst-cleanup4aux.o
 test-extras += $(modules-names) tst-cleanup4aux
 test-modules = $(addprefix $(objpfx),$(addsuffix .so,$(modules-names)))
@@ -319,7 +318,6 @@ tst-tls5modc.so-no-z-defs = yes
 tst-tls5modd.so-no-z-defs = yes
 tst-tls5mode.so-no-z-defs = yes
 tst-tls5modf.so-no-z-defs = yes
-tst-tls7mod.so-no-z-defs = yes
 
 ifeq ($(build-shared),yes)
 # Build all the modules even when not actually running test programs.
@@ -482,12 +480,6 @@ $(objpfx)tst-tls5: $(objpfx)tst-tls5mod.so $(shared-thread-library)
 LDFLAGS-tst-tls5 = $(no-as-needed)
 LDFLAGS-tst-tls5mod.so = -Wl,-soname,tst-tls5mod.so
 
-# ensure free(malloc()) isn't optimized out
-CFLAGS-tst-tls7.c = -fno-builtin-malloc -fno-builtin-free
-$(objpfx)tst-tls7: $(libdl) $(shared-thread-library)
-$(objpfx)tst-tls7.out: $(objpfx)tst-tls7mod.so
-$(objpfx)tst-tls7mod.so: $(shared-thread-library)
-
 ifeq ($(build-shared),yes)
 ifeq ($(run-built-tests),yes)
 tests: $(objpfx)tst-tls6.out

nptl/allocatestack.c

@@ -1173,18 +1173,13 @@ 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[map->l_tls_modid].pointer.val = dest;
+  dtv[map->l_tls_modid].pointer.is_static = true;
+
   /* 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);
-
-  /* Fill in the DTV slot so that a later LD/GD access will find it.  */
-  dtv[map->l_tls_modid].pointer.is_static = true;
-  /* Pairs against the read barrier in tls_get_attr_tail, guaranteeing
-     any thread waiting for an update to pointer.val sees the
-     initimage write.  */
-  atomic_write_barrier ();
-  dtv[map->l_tls_modid].pointer.val = dest;
-
 }
 
 void

nptl/tst-tls7.c

@@ -1,143 +0,0 @@
-/* Copyright (C) 2013 Free Software Foundation, Inc.
-   This file is part of the GNU C Library.
-
-   The GNU C Library is free software; you can redistribute it and/or
-   modify it under the terms of the GNU Lesser General Public
-   License as published by the Free Software Foundation; either
-   version 2.1 of the License, or (at your option) any later version.
-
-   The GNU C Library is distributed in the hope that it will be useful,
-   but WITHOUT ANY WARRANTY; without even the implied warranty of
-   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-   Lesser General Public License for more details.
-
-   You should have received a copy of the GNU Lesser General Public
-   License along with the GNU C Library; if not, see
-   <http://www.gnu.org/licenses/>.  */
-
-
-/* This test checks that TLS in a dlopened object works when first accessed
-   from a signal handler.  */
-
-#include <assert.h>
-#include <atomic.h>
-#include <dlfcn.h>
-#include <pthread.h>
-#include <semaphore.h>
-#include <signal.h>
-#include <stdio.h>
-#include <stdlib.h>
-
-void *
-spin (void *ignored)
-{
-  while (1)
-    {
-      /* busywork */
-      free (malloc (128));
-    }
-
-  /* never reached */
-  return NULL;
-}
-
-static void (*tls7mod_action) (int, siginfo_t *, void *);
-
-static void
-action (int signo, siginfo_t *info, void *ignored)
-{
-  sem_t *sem = info->si_value.sival_ptr;
-
-  atomic_read_barrier ();
-  assert (tls7mod_action != NULL);
-  (*tls7mod_action) (signo, info, ignored);
-
-  /* This sem_post may trigger dlclose, which will invalidate tls7mod_action.
-     It is important to do that only after tls7mod_action is no longer
-     active.  */
-  sem_post (sem);
-}
-
-int
-do_test (void)
-{
-  pthread_t th[10];
-
-  for (int i = 0; i < 10; ++i)
-    {
-      if (pthread_create (&th[i], NULL, spin, NULL))
-        {
-          puts ("pthread_create failed");
-          exit (1);
-        }
-    }
-#define NITERS 75
-
-  for (int i = 0; i < NITERS; ++i)
-    {
-      void *h = dlopen ("tst-tls7mod.so", RTLD_LAZY);
-      if (h == NULL)
-        {
-          puts ("dlopen failed");
-          exit (1);
-        }
-
-      tls7mod_action = dlsym (h, "action");
-      if (tls7mod_action == NULL)
-        {
-          puts ("dlsym for action failed");
-          exit (1);
-        }
-      atomic_write_barrier ();
-
-      struct sigaction sa;
-      sa.sa_sigaction = action;
-      sigemptyset (&sa.sa_mask);
-      sa.sa_flags = SA_SIGINFO;
-      if (sigaction (SIGUSR1, &sa, NULL))
-        {
-          puts ("sigaction failed");
-          exit (1);
-        }
-
-      sem_t sem;
-      if (sem_init (&sem, 0, 0))
-        {
-          puts ("sem_init failed");
-        }
-
-      sigval_t val;
-      val.sival_ptr = &sem;
-      for (int i = 0; i < 10; ++i)
-        {
-          if (pthread_sigqueue (th[i], SIGUSR1, val))
-            {
-              puts ("pthread_sigqueue failed");
-            }
-        }
-
-
-      for (int i = 0; i < 10; ++i)
-        {
-          if (sem_wait (&sem))
-          {
-            puts ("sem_wait failed");
-          }
-        }
-
-      /* Paranoia.  */
-      tls7mod_action = NULL;
-
-      if (dlclose (h))
-        {
-          puts ("dlclose failed");
-          exit (1);
-        }
-    }
-  return 0;
-}
-
-#define TIMEOUT 8
-
-#define TEST_FUNCTION do_test ()
-#include "../test-skeleton.c"

nptl/tst-tls7mod.c

@@ -1,40 +0,0 @@
-/* Copyright (C) 2013 Free Software Foundation, Inc.
-   This file is part of the GNU C Library.
-
-   The GNU C Library is free software; you can redistribute it and/or
-   modify it under the terms of the GNU Lesser General Public
-   License as published by the Free Software Foundation; either
-   version 2.1 of the License, or (at your option) any later version.
-
-   The GNU C Library is distributed in the hope that it will be useful,
-   but WITHOUT ANY WARRANTY; without even the implied warranty of
-   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-   Lesser General Public License for more details.
-
-   You should have received a copy of the GNU Lesser General Public
-   License along with the GNU C Library; if not, see
-   <http://www.gnu.org/licenses/>.  */
-
-/* Dynamic module with TLS to be accessed by a signal handler to check safety
-   of that mode. */
-
-#include <semaphore.h>
-#include <signal.h>
-#include <unistd.h>
-
-/* This is an unlikely value to see in incorrectly initialized TLS
-   block -- make sure we're initialized properly. */
-static __thread intptr_t tls_data = 0xdeadbeef;
-
-void
-action (int signo, siginfo_t *info, void *ignored)
-{
-  if (tls_data != 0xdeadbeef)
-    {
-      write (STDOUT_FILENO, "wrong TLS value\n", 17);
-      _exit (1);
-    }
-
-  /* arbitrary choice, just write something unique-ish. */
-  tls_data = (intptr_t) info;
-}