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Diffstat (limited to 'REORG.TODO/nptl/sem_wait.c')
-rw-r--r-- | REORG.TODO/nptl/sem_wait.c | 106 |
1 files changed, 106 insertions, 0 deletions
diff --git a/REORG.TODO/nptl/sem_wait.c b/REORG.TODO/nptl/sem_wait.c new file mode 100644 index 0000000000..625bf08c83 --- /dev/null +++ b/REORG.TODO/nptl/sem_wait.c @@ -0,0 +1,106 @@ +/* sem_wait -- wait on a semaphore. Generic futex-using version. + Copyright (C) 2003-2017 Free Software Foundation, Inc. + This file is part of the GNU C Library. + Contributed by Paul Mackerras <paulus@au.ibm.com>, 2003. + + 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 <lowlevellock.h> /* lll_futex* used by the old code. */ +#include "sem_waitcommon.c" + +int +__new_sem_wait (sem_t *sem) +{ + /* We need to check whether we need to act upon a cancellation request here + because POSIX specifies that cancellation points "shall occur" in + sem_wait and sem_timedwait, which also means that they need to check + this regardless whether they block or not (unlike "may occur" + functions). See the POSIX Rationale for this requirement: Section + "Thread Cancellation Overview" [1] and austin group issue #1076 [2] + for thoughs on why this may be a suboptimal design. + + [1] http://pubs.opengroup.org/onlinepubs/9699919799/xrat/V4_xsh_chap02.html + [2] http://austingroupbugs.net/view.php?id=1076 for thoughts on why this + */ + __pthread_testcancel (); + + if (__new_sem_wait_fast ((struct new_sem *) sem, 0) == 0) + return 0; + else + return __new_sem_wait_slow((struct new_sem *) sem, NULL); +} +versioned_symbol (libpthread, __new_sem_wait, sem_wait, GLIBC_2_1); + +#if SHLIB_COMPAT (libpthread, GLIBC_2_0, GLIBC_2_1) +int +attribute_compat_text_section +__old_sem_wait (sem_t *sem) +{ + int *futex = (int *) sem; + int err; + + do + { + if (atomic_decrement_if_positive (futex) > 0) + return 0; + + /* Enable asynchronous cancellation. Required by the standard. */ + int oldtype = __pthread_enable_asynccancel (); + + /* Always assume the semaphore is shared. */ + err = lll_futex_wait (futex, 0, LLL_SHARED); + + /* Disable asynchronous cancellation. */ + __pthread_disable_asynccancel (oldtype); + } + while (err == 0 || err == -EWOULDBLOCK); + + __set_errno (-err); + return -1; +} + +compat_symbol (libpthread, __old_sem_wait, sem_wait, GLIBC_2_0); +#endif + +int +__new_sem_trywait (sem_t *sem) +{ + /* We must not fail spuriously, so require a definitive result even if this + may lead to a long execution time. */ + if (__new_sem_wait_fast ((struct new_sem *) sem, 1) == 0) + return 0; + __set_errno (EAGAIN); + return -1; +} +versioned_symbol (libpthread, __new_sem_trywait, sem_trywait, GLIBC_2_1); +#if SHLIB_COMPAT (libpthread, GLIBC_2_0, GLIBC_2_1) +int +__old_sem_trywait (sem_t *sem) +{ + int *futex = (int *) sem; + int val; + + if (*futex > 0) + { + val = atomic_decrement_if_positive (futex); + if (val > 0) + return 0; + } + + __set_errno (EAGAIN); + return -1; +} +compat_symbol (libpthread, __old_sem_trywait, sem_trywait, GLIBC_2_0); +#endif |