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Diffstat (limited to 'nptl/pthread_cond_signal.c')
| -rw-r--r-- | nptl/pthread_cond_signal.c | 100 |
1 files changed, 0 insertions, 100 deletions
diff --git a/nptl/pthread_cond_signal.c b/nptl/pthread_cond_signal.c deleted file mode 100644 index db0698c66c..0000000000 --- a/nptl/pthread_cond_signal.c +++ /dev/null @@ -1,100 +0,0 @@ -/* Copyright (C) 2003-2017 Free Software Foundation, Inc. - This file is part of the GNU C Library. - Contributed by Martin Schwidefsky <schwidefsky@de.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 <endian.h> -#include <errno.h> -#include <sysdep.h> -#include <futex-internal.h> -#include <pthread.h> -#include <pthreadP.h> -#include <atomic.h> -#include <stdint.h> - -#include <shlib-compat.h> -#include <stap-probe.h> - -#include "pthread_cond_common.c" - -/* See __pthread_cond_wait for a high-level description of the algorithm. */ -int -__pthread_cond_signal (pthread_cond_t *cond) -{ - LIBC_PROBE (cond_signal, 1, cond); - - /* First check whether there are waiters. Relaxed MO is fine for that for - the same reasons that relaxed MO is fine when observing __wseq (see - below). */ - unsigned int wrefs = atomic_load_relaxed (&cond->__data.__wrefs); - if (wrefs >> 3 == 0) - return 0; - int private = __condvar_get_private (wrefs); - - __condvar_acquire_lock (cond, private); - - /* Load the waiter sequence number, which represents our relative ordering - to any waiters. Relaxed MO is sufficient for that because: - 1) We can pick any position that is allowed by external happens-before - constraints. In particular, if another __pthread_cond_wait call - happened before us, this waiter must be eligible for being woken by - us. The only way do establish such a happens-before is by signaling - while having acquired the mutex associated with the condvar and - ensuring that the signal's critical section happens after the waiter. - Thus, the mutex ensures that we see that waiter's __wseq increase. - 2) Once we pick a position, we do not need to communicate this to the - program via a happens-before that we set up: First, any wake-up could - be a spurious wake-up, so the program must not interpret a wake-up as - an indication that the waiter happened before a particular signal; - second, a program cannot detect whether a waiter has not yet been - woken (i.e., it cannot distinguish between a non-woken waiter and one - that has been woken but hasn't resumed execution yet), and thus it - cannot try to deduce that a signal happened before a particular - waiter. */ - unsigned long long int wseq = __condvar_load_wseq_relaxed (cond); - unsigned int g1 = (wseq & 1) ^ 1; - wseq >>= 1; - bool do_futex_wake = false; - - /* If G1 is still receiving signals, we put the signal there. If not, we - check if G2 has waiters, and if so, quiesce and switch G1 to the former - G2; if this results in a new G1 with waiters (G2 might have cancellations - already, see __condvar_quiesce_and_switch_g1), we put the signal in the - new G1. */ - if ((cond->__data.__g_size[g1] != 0) - || __condvar_quiesce_and_switch_g1 (cond, wseq, &g1, private)) - { - /* Add a signal. Relaxed MO is fine because signaling does not need to - establish a happens-before relation (see above). We do not mask the - release-MO store when initializing a group in - __condvar_quiesce_and_switch_g1 because we use an atomic - read-modify-write and thus extend that store's release sequence. */ - atomic_fetch_add_relaxed (cond->__data.__g_signals + g1, 2); - cond->__data.__g_size[g1]--; - /* TODO Only set it if there are indeed futex waiters. */ - do_futex_wake = true; - } - - __condvar_release_lock (cond, private); - - if (do_futex_wake) - futex_wake (cond->__data.__g_signals + g1, 1, private); - - return 0; -} - -versioned_symbol (libpthread, __pthread_cond_signal, pthread_cond_signal, - GLIBC_2_3_2); |