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Diffstat (limited to 'sysdeps/nacl/exit-thread.h')
| -rw-r--r-- | sysdeps/nacl/exit-thread.h | 80 |
1 files changed, 0 insertions, 80 deletions
diff --git a/sysdeps/nacl/exit-thread.h b/sysdeps/nacl/exit-thread.h deleted file mode 100644 index b9dce6ec0e..0000000000 --- a/sysdeps/nacl/exit-thread.h +++ /dev/null @@ -1,80 +0,0 @@ -/* Call to terminate the current thread. NaCl version. - Copyright (C) 2015-2017 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/>. */ - -#include <assert.h> -#include <atomic.h> -#include <futex-internal.h> -#include <nacl-interfaces.h> -#include <nptl/pthreadP.h> - -/* This causes the current thread to exit, without affecting other - threads in the process if there are any. If there are no other - threads left, then this has the effect of _exit (0). */ - -static inline void __attribute__ ((noreturn, always_inline, unused)) -__exit_thread (void) -{ - struct pthread *pd = THREAD_SELF; - - /* The generic logic for pthread_join and stack/descriptor reuse is - based on the Linux kernel feature that will clear and futex-wake - a designated address as a final part of thread teardown. Correct - synchronization relies on the fact that these happen only after - there is no possibility of user code touching or examining the - late thread's stack. - - The NaCl system interface implements half of this: it clears a - word after the thread's user stack is safely dead, but it does - not futex-wake the location. So, some shenanigans are required. - We change and futex-wake the location here, so as to wake up any - blocked pthread_join (i.e. lll_wait_tid) or pthread_timedjoin_np - (i.e. lll_timedwait_tid). However, that's before we have safely - vacated the stack. So instead of clearing the location, we set - it to a special magic value, NACL_EXITING_TID. This counts as a - "live thread" value for all the generic logic, but is recognized - specially in lll_wait_tid and lll_timedwait_tid (lowlevellock.h). - Once it has this value, lll_wait_tid will busy-wait for the - location to be cleared to zero by the NaCl system code. Only then - is the stack actually safe to reuse. */ - - if (!IS_DETACHED (pd)) - { - /* The magic value must not be one that could ever be a valid - TID value. See pthread-pids.h about the low bit. */ - assert (NACL_EXITING_TID & 1); - - /* The magic value must not be one that has the "free" flag - (i.e. sign bit) set. If that bit is set, then the - descriptor could be reused for a new thread. */ - assert (NACL_EXITING_TID > 0); - - atomic_store_relaxed (&pd->tid, NACL_EXITING_TID); - futex_wake ((unsigned int *) &pd->tid, 1, FUTEX_PRIVATE); - } - - /* This clears PD->tid some time after the thread stack can never - be touched again. Unfortunately, it does not also do a - futex-wake at that time (as Linux does via CLONE_CHILD_CLEARTID - and set_tid_address). So lll_wait_tid does some busy-waiting. */ - __nacl_irt_thread.thread_exit (&pd->tid); - - /* That never returns unless something is severely and unrecoverably wrong. - If it ever does, try to make sure we crash. */ - while (1) - __builtin_trap (); -} |