sysdeps/nptl/dl-thread_gscope_wait.c

   1 /* Out-of-line notification function for the GSCOPE locking mechanism.
   2    Copyright (C) 2007-2023 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <https://www.gnu.org/licenses/>.  */
  18
  19 #include <nptl/descr.h>
  20 #include <futex-internal.h>
  21 #include <ldsodefs.h>
  22 #include <list.h>
  23 #include <lowlevellock.h>
  24
  25 void
  26 __thread_gscope_wait (void)
  27 {
  28   lll_lock (GL (dl_stack_cache_lock), LLL_PRIVATE);
  29
  30   struct pthread *self = THREAD_SELF;
  31
  32   /* Iterate over the list with system-allocated threads first.  */
  33   list_t *runp;
  34   list_for_each (runp, &GL (dl_stack_used))
  35     {
  36       struct pthread *t = list_entry (runp, struct pthread, list);
  37       if (t == self || t->header.gscope_flag == THREAD_GSCOPE_FLAG_UNUSED)
  38         continue;
  39
  40       int *const gscope_flagp = &t->header.gscope_flag;
  41
  42       /* We have to wait until this thread is done with the global
  43          scope.  First tell the thread that we are waiting and
  44          possibly have to be woken.  */
  45       if (atomic_compare_and_exchange_bool_acq (gscope_flagp,
  46                                                 THREAD_GSCOPE_FLAG_WAIT,
  47                                                 THREAD_GSCOPE_FLAG_USED))
  48         continue;
  49
  50       do
  51         futex_wait_simple ((unsigned int *) gscope_flagp,
  52                            THREAD_GSCOPE_FLAG_WAIT, FUTEX_PRIVATE);
  53       while (*gscope_flagp == THREAD_GSCOPE_FLAG_WAIT);
  54     }
  55
  56   /* Now the list with threads using user-allocated stacks.  */
  57   list_for_each (runp, &GL (dl_stack_user))
  58     {
  59       struct pthread *t = list_entry (runp, struct pthread, list);
  60       if (t == self || t->header.gscope_flag == THREAD_GSCOPE_FLAG_UNUSED)
  61         continue;
  62
  63       int *const gscope_flagp = &t->header.gscope_flag;
  64
  65       /* We have to wait until this thread is done with the global
  66          scope.  First tell the thread that we are waiting and
  67          possibly have to be woken.  */
  68       if (atomic_compare_and_exchange_bool_acq (gscope_flagp,
  69                                                 THREAD_GSCOPE_FLAG_WAIT,
  70                                                 THREAD_GSCOPE_FLAG_USED))
  71         continue;
  72
  73       do
  74         futex_wait_simple ((unsigned int *) gscope_flagp,
  75                            THREAD_GSCOPE_FLAG_WAIT, FUTEX_PRIVATE);
  76       while (*gscope_flagp == THREAD_GSCOPE_FLAG_WAIT);
  77     }
  78
  79   lll_unlock (GL (dl_stack_cache_lock), LLL_PRIVATE);
  80 }