| 1 | /* Out-of-line notification function for the GSCOPE locking mechanism. |
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| 2 | Copyright (C) 2007-2024 Free Software Foundation, Inc. |
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| 3 | This file is part of the GNU C Library. |
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| 4 | |
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| 5 | The GNU C Library is free software; you can redistribute it and/or |
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| 6 | modify it under the terms of the GNU Lesser General Public |
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| 7 | License as published by the Free Software Foundation; either |
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| 8 | version 2.1 of the License, or (at your option) any later version. |
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| 9 | |
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| 10 | The GNU C Library is distributed in the hope that it will be useful, |
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| 11 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
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| 12 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
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| 13 | Lesser General Public License for more details. |
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| 14 | |
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| 15 | You should have received a copy of the GNU Lesser General Public |
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| 16 | License along with the GNU C Library; if not, see |
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| 17 | <https://www.gnu.org/licenses/>. */ |
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| 18 | |
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| 19 | #include <nptl/descr.h> |
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| 20 | #include <futex-internal.h> |
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| 21 | #include <ldsodefs.h> |
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| 22 | #include <list.h> |
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| 23 | #include <lowlevellock.h> |
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| 24 | |
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| 25 | void |
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| 26 | __thread_gscope_wait (void) |
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| 27 | { |
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| 28 | lll_lock (GL (dl_stack_cache_lock), LLL_PRIVATE); |
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| 29 | |
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| 30 | struct pthread *self = THREAD_SELF; |
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| 31 | |
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| 32 | /* Iterate over the list with system-allocated threads first. */ |
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| 33 | list_t *runp; |
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| 34 | list_for_each (runp, &GL (dl_stack_used)) |
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| 35 | { |
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| 36 | struct pthread *t = list_entry (runp, struct pthread, list); |
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| 37 | if (t == self || t->header.gscope_flag == THREAD_GSCOPE_FLAG_UNUSED) |
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| 38 | continue; |
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| 39 | |
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| 40 | int *const gscope_flagp = &t->header.gscope_flag; |
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| 41 | |
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| 42 | /* We have to wait until this thread is done with the global |
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| 43 | scope. First tell the thread that we are waiting and |
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| 44 | possibly have to be woken. */ |
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| 45 | if (atomic_compare_and_exchange_bool_acq (gscope_flagp, |
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| 46 | THREAD_GSCOPE_FLAG_WAIT, |
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| 47 | THREAD_GSCOPE_FLAG_USED)) |
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| 48 | continue; |
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| 49 | |
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| 50 | do |
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| 51 | futex_wait_simple (futex_word: (unsigned int *) gscope_flagp, |
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| 52 | THREAD_GSCOPE_FLAG_WAIT, FUTEX_PRIVATE); |
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| 53 | while (*gscope_flagp == THREAD_GSCOPE_FLAG_WAIT); |
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| 54 | } |
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| 55 | |
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| 56 | /* Now the list with threads using user-allocated stacks. */ |
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| 57 | list_for_each (runp, &GL (dl_stack_user)) |
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| 58 | { |
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| 59 | struct pthread *t = list_entry (runp, struct pthread, list); |
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| 60 | if (t == self || t->header.gscope_flag == THREAD_GSCOPE_FLAG_UNUSED) |
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| 61 | continue; |
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| 62 | |
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| 63 | int *const gscope_flagp = &t->header.gscope_flag; |
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| 64 | |
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| 65 | /* We have to wait until this thread is done with the global |
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| 66 | scope. First tell the thread that we are waiting and |
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| 67 | possibly have to be woken. */ |
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| 68 | if (atomic_compare_and_exchange_bool_acq (gscope_flagp, |
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| 69 | THREAD_GSCOPE_FLAG_WAIT, |
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| 70 | THREAD_GSCOPE_FLAG_USED)) |
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| 71 | continue; |
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| 72 | |
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| 73 | do |
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| 74 | futex_wait_simple (futex_word: (unsigned int *) gscope_flagp, |
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| 75 | THREAD_GSCOPE_FLAG_WAIT, FUTEX_PRIVATE); |
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| 76 | while (*gscope_flagp == THREAD_GSCOPE_FLAG_WAIT); |
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| 77 | } |
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| 78 | |
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| 79 | lll_unlock (GL (dl_stack_cache_lock), LLL_PRIVATE); |
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| 80 | } |
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| 81 | |
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