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Diffstat (limited to 'libgomp/team.c')
| -rw-r--r-- | libgomp/team.c | 344 |
1 files changed, 344 insertions, 0 deletions
diff --git a/libgomp/team.c b/libgomp/team.c new file mode 100644 index 00000000000..1d8efb688af --- /dev/null +++ b/libgomp/team.c @@ -0,0 +1,344 @@ +/* Copyright (C) 2005 Free Software Foundation, Inc. + Contributed by Richard Henderson <rth@redhat.com>. + + This file is part of the GNU OpenMP Library (libgomp). + + Libgomp 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. + + Libgomp 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 libgomp; see the file COPYING.LIB. If not, write to the + Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, + MA 02110-1301, USA. */ + +/* As a special exception, if you link this library with other files, some + of which are compiled with GCC, to produce an executable, this library + does not by itself cause the resulting executable to be covered by the + GNU General Public License. This exception does not however invalidate + any other reasons why the executable file might be covered by the GNU + General Public License. */ + +/* This file handles the maintainence of threads in response to team + creation and termination. */ + +#include "libgomp.h" +#include <stdlib.h> +#include <string.h> + + +/* This array manages threads spawned from the top level, which will + return to the idle loop once the current PARALLEL construct ends. */ +static struct gomp_thread **gomp_threads; +static unsigned gomp_threads_size; +static unsigned gomp_threads_used; + +/* This attribute contains PTHREAD_CREATE_DETACHED. */ +static pthread_attr_t gomp_thread_attr; + +/* This barrier holds and releases threads waiting in gomp_threads. */ +static gomp_barrier_t gomp_threads_dock; + +/* This is the libgomp per-thread data structure. */ +#ifdef HAVE_TLS +__thread struct gomp_thread gomp_tls_data; +#else +pthread_key_t gomp_tls_key; +#endif + + +/* This structure is used to communicate across pthread_create. */ + +struct gomp_thread_start_data +{ + struct gomp_team_state ts; + void (*fn) (void *); + void *fn_data; + bool nested; +}; + + +/* This function is a pthread_create entry point. This contains the idle + loop in which a thread waits to be called up to become part of a team. */ + +static void * +gomp_thread_start (void *xdata) +{ + struct gomp_thread_start_data *data = xdata; + struct gomp_thread *thr; + void (*local_fn) (void *); + void *local_data; + +#ifdef HAVE_TLS + thr = &gomp_tls_data; +#else + struct gomp_thread local_thr; + thr = &local_thr; + pthread_setspecific (gomp_tls_key, thr); +#endif + gomp_sem_init (&thr->release, 0); + + /* Extract what we need from data. */ + local_fn = data->fn; + local_data = data->fn_data; + thr->ts = data->ts; + + thr->ts.team->ordered_release[thr->ts.team_id] = &thr->release; + + if (data->nested) + { + gomp_barrier_wait (&thr->ts.team->barrier); + local_fn (local_data); + gomp_barrier_wait (&thr->ts.team->barrier); + } + else + { + gomp_threads[thr->ts.team_id] = thr; + + gomp_barrier_wait (&gomp_threads_dock); + do + { + struct gomp_team *team; + + local_fn (local_data); + + /* Clear out the team and function data. This is a debugging + signal that we're in fact back in the dock. */ + team = thr->ts.team; + thr->fn = NULL; + thr->data = NULL; + thr->ts.team = NULL; + thr->ts.work_share = NULL; + thr->ts.team_id = 0; + thr->ts.work_share_generation = 0; + thr->ts.static_trip = 0; + + gomp_barrier_wait (&team->barrier); + gomp_barrier_wait (&gomp_threads_dock); + + local_fn = thr->fn; + local_data = thr->data; + } + while (local_fn); + } + + return NULL; +} + + +/* Create a new team data structure. */ + +static struct gomp_team * +new_team (unsigned nthreads, struct gomp_work_share *work_share) +{ + struct gomp_team *team; + size_t size; + + size = sizeof (*team) + nthreads * sizeof (team->ordered_release[0]); + team = gomp_malloc (size); + gomp_mutex_init (&team->work_share_lock); + + team->work_shares = gomp_malloc (4 * sizeof (struct gomp_work_share *)); + team->generation_mask = 3; + team->oldest_live_gen = work_share == NULL; + team->num_live_gen = work_share != NULL; + team->work_shares[0] = work_share; + + team->nthreads = nthreads; + gomp_barrier_init (&team->barrier, nthreads); + + gomp_sem_init (&team->master_release, 0); + team->ordered_release[0] = &team->master_release; + + return team; +} + + +/* Free a team data structure. */ + +static void +free_team (struct gomp_team *team) +{ + free (team->work_shares); + gomp_mutex_destroy (&team->work_share_lock); + gomp_barrier_destroy (&team->barrier); + gomp_sem_destroy (&team->master_release); + free (team); +} + + +/* Launch a team. */ + +void +gomp_team_start (void (*fn) (void *), void *data, unsigned nthreads, + struct gomp_work_share *work_share) +{ + struct gomp_thread_start_data *start_data; + struct gomp_thread *thr, *nthr; + struct gomp_team *team; + bool nested; + unsigned i, n, old_threads_used = 0; + + thr = gomp_thread (); + nested = thr->ts.team != NULL; + + team = new_team (nthreads, work_share); + + /* Always save the previous state, even if this isn't a nested team. + In particular, we should save any work share state from an outer + orphaned work share construct. */ + team->prev_ts = thr->ts; + + thr->ts.team = team; + thr->ts.work_share = work_share; + thr->ts.team_id = 0; + thr->ts.work_share_generation = 0; + thr->ts.static_trip = 0; + + if (nthreads == 1) + return; + + i = 1; + + /* We only allow the reuse of idle threads for non-nested PARALLEL + regions. This appears to be implied by the semantics of + threadprivate variables, but perhaps that's reading too much into + things. Certainly it does prevent any locking problems, since + only the initial program thread will modify gomp_threads. */ + if (!nested) + { + old_threads_used = gomp_threads_used; + + if (nthreads <= old_threads_used) + n = nthreads; + else if (old_threads_used == 0) + { + n = 0; + gomp_barrier_init (&gomp_threads_dock, nthreads); + } + else + { + n = old_threads_used; + + /* Increase the barrier threshold to make sure all new + threads arrive before the team is released. */ + gomp_barrier_reinit (&gomp_threads_dock, nthreads); + } + + /* Not true yet, but soon will be. We're going to release all + threads from the dock, and those that aren't part of the + team will exit. */ + gomp_threads_used = nthreads; + + /* Release existing idle threads. */ + for (; i < n; ++i) + { + nthr = gomp_threads[i]; + nthr->ts.team = team; + nthr->ts.work_share = work_share; + nthr->ts.team_id = i; + nthr->ts.work_share_generation = 0; + nthr->ts.static_trip = 0; + nthr->fn = fn; + nthr->data = data; + team->ordered_release[i] = &nthr->release; + } + + if (i == nthreads) + goto do_release; + + /* If necessary, expand the size of the gomp_threads array. It is + expected that changes in the number of threads is rare, thus we + make no effort to expand gomp_threads_size geometrically. */ + if (nthreads >= gomp_threads_size) + { + gomp_threads_size = nthreads + 1; + gomp_threads + = gomp_realloc (gomp_threads, + gomp_threads_size + * sizeof (struct gomp_thread_data *)); + } + } + + start_data = alloca (sizeof (struct gomp_thread_start_data) * (nthreads-i)); + + /* Launch new threads. */ + for (; i < nthreads; ++i, ++start_data) + { + pthread_t pt; + int err; + + start_data->ts.team = team; + start_data->ts.work_share = work_share; + start_data->ts.team_id = i; + start_data->ts.work_share_generation = 0; + start_data->ts.static_trip = 0; + start_data->fn = fn; + start_data->fn_data = data; + start_data->nested = nested; + + err = pthread_create (&pt, &gomp_thread_attr, + gomp_thread_start, start_data); + if (err != 0) + gomp_fatal ("Thread creation failed: %s", strerror (err)); + } + + do_release: + gomp_barrier_wait (nested ? &team->barrier : &gomp_threads_dock); + + /* Decrease the barrier threshold to match the number of threads + that should arrive back at the end of this team. The extra + threads should be exiting. Note that we arrange for this test + to never be true for nested teams. */ + if (nthreads < old_threads_used) + gomp_barrier_reinit (&gomp_threads_dock, nthreads); +} + + +/* Terminate the current team. This is only to be called by the master + thread. We assume that we must wait for the other threads. */ + +void +gomp_team_end (void) +{ + struct gomp_thread *thr = gomp_thread (); + struct gomp_team *team = thr->ts.team; + + gomp_barrier_wait (&team->barrier); + + thr->ts = team->prev_ts; + + free_team (team); +} + + +/* Constructors for this file. */ + +static void __attribute__((constructor)) +initialize_team (void) +{ + struct gomp_thread *thr; + +#ifndef HAVE_TLS + static struct gomp_thread initial_thread_tls_data; + + pthread_key_create (&gomp_tls_key, NULL); + pthread_setspecific (gomp_tls_key, &initial_thread_tls_data); +#endif + +#ifdef HAVE_TLS + thr = &gomp_tls_data; +#else + thr = &initial_thread_tls_data; +#endif + gomp_sem_init (&thr->release, 0); + + pthread_attr_init (&gomp_thread_attr); + pthread_attr_setdetachstate (&gomp_thread_attr, PTHREAD_CREATE_DETACHED); +} |