diff options
Diffstat (limited to 'REORG.TODO/nptl/pthread_cond_destroy.c')
-rw-r--r-- | REORG.TODO/nptl/pthread_cond_destroy.c | 62 |
1 files changed, 62 insertions, 0 deletions
diff --git a/REORG.TODO/nptl/pthread_cond_destroy.c b/REORG.TODO/nptl/pthread_cond_destroy.c new file mode 100644 index 0000000000..fc65dca78c --- /dev/null +++ b/REORG.TODO/nptl/pthread_cond_destroy.c @@ -0,0 +1,62 @@ +/* Copyright (C) 2002-2017 Free Software Foundation, Inc. + This file is part of the GNU C Library. + Contributed by Ulrich Drepper <drepper@redhat.com>, 2002. + + 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 <errno.h> +#include <shlib-compat.h> +#include "pthreadP.h" +#include <stap-probe.h> +#include <atomic.h> +#include <futex-internal.h> + +#include "pthread_cond_common.c" + +/* See __pthread_cond_wait for a high-level description of the algorithm. + + A correct program must make sure that no waiters are blocked on the condvar + when it is destroyed, and that there are no concurrent signals or + broadcasts. To wake waiters reliably, the program must signal or + broadcast while holding the mutex or after having held the mutex. It must + also ensure that no signal or broadcast are still pending to unblock + waiters; IOW, because waiters can wake up spuriously, the program must + effectively ensure that destruction happens after the execution of those + signal or broadcast calls. + Thus, we can assume that all waiters that are still accessing the condvar + have been woken. We wait until they have confirmed to have woken up by + decrementing __wrefs. */ +int +__pthread_cond_destroy (pthread_cond_t *cond) +{ + LIBC_PROBE (cond_destroy, 1, cond); + + /* Set the wake request flag. We could also spin, but destruction that is + concurrent with still-active waiters is probably neither common nor + performance critical. Acquire MO to synchronize with waiters confirming + that they finished. */ + unsigned int wrefs = atomic_fetch_or_acquire (&cond->__data.__wrefs, 4); + int private = __condvar_get_private (wrefs); + while (wrefs >> 3 != 0) + { + futex_wait_simple (&cond->__data.__wrefs, wrefs, private); + /* See above. */ + wrefs = atomic_load_acquire (&cond->__data.__wrefs); + } + /* The memory the condvar occupies can now be reused. */ + return 0; +} +versioned_symbol (libpthread, __pthread_cond_destroy, + pthread_cond_destroy, GLIBC_2_3_2); |