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re PR libgomp/51298 (libgomp team_barrier locking failures)

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PR libgomp/51298
	* config/linux/bar.h: Use atomic rather than sync builtins.
	* config/linux/bar.c: Likewise.  Add missing acquire
	synchronisation on generation field.
	* task.c (gomp_barrier_handle_tasks): Regain lock so as to not
	double unlock.

From-SVN: r181833
This commit is contained in:
Alan Modra 2011-11-30 15:14:13 +10:30 committed by Alan Modra
parent b40c885f18
commit ab6dd406ba
4 changed files with 35 additions and 20 deletions
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9
libgomp/ChangeLog
View File

@ -1,3 +1,12 @@
2011-11-30 Alan Modra <amodra@gmail.com>
PR libgomp/51298
* config/linux/bar.h: Use atomic rather than sync builtins.
* config/linux/bar.c: Likewise. Add missing acquire
synchronisation on generation field.
* task.c (gomp_barrier_handle_tasks): Regain lock so as to not
double unlock.
2011-11-30 Alan Modra <amodra@gmail.com>
* ordered.c (gomp_ordered_sync): Add MEMMODEL_ACQ_REL fence.

30
libgomp/config/linux/bar.c
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@ -1,4 +1,4 @@
/* Copyright (C) 2005, 2008, 2009 Free Software Foundation, Inc.
/* Copyright (C) 2005, 2008, 2009, 2011 Free Software Foundation, Inc.
Contributed by Richard Henderson <rth@redhat.com>.
This file is part of the GNU OpenMP Library (libgomp).
@ -37,17 +37,15 @@ gomp_barrier_wait_end (gomp_barrier_t *bar, gomp_barrier_state_t state)
{
/* Next time we'll be awaiting TOTAL threads again. */
bar->awaited = bar->total;
atomic_write_barrier ();
bar->generation += 4;
__atomic_store_n (&bar->generation, bar->generation + 4,
MEMMODEL_RELEASE);
futex_wake ((int *) &bar->generation, INT_MAX);
}
else
{
unsigned int generation = state;
do
do_wait ((int *) &bar->generation, generation);
while (bar->generation == generation);
do_wait ((int *) &bar->generation, state);
while (__atomic_load_n (&bar->generation, MEMMODEL_ACQUIRE) == state);
}
}
@ -81,15 +79,15 @@ gomp_team_barrier_wake (gomp_barrier_t *bar, int count)
void
gomp_team_barrier_wait_end (gomp_barrier_t *bar, gomp_barrier_state_t state)
{
unsigned int generation;
unsigned int generation, gen;
if (__builtin_expect ((state & 1) != 0, 0))
{
/* Next time we'll be awaiting TOTAL threads again. */
struct gomp_thread *thr = gomp_thread ();
struct gomp_team *team = thr->ts.team;
bar->awaited = bar->total;
atomic_write_barrier ();
if (__builtin_expect (team->task_count, 0))
{
gomp_barrier_handle_tasks (state);
@ -97,7 +95,7 @@ gomp_team_barrier_wait_end (gomp_barrier_t *bar, gomp_barrier_state_t state)
}
else
{
bar->generation = state + 3;
__atomic_store_n (&bar->generation, state + 3, MEMMODEL_RELEASE);
futex_wake ((int *) &bar->generation, INT_MAX);
return;
}
@ -107,12 +105,16 @@ gomp_team_barrier_wait_end (gomp_barrier_t *bar, gomp_barrier_state_t state)
do
{
do_wait ((int *) &bar->generation, generation);
if (__builtin_expect (bar->generation & 1, 0))
gomp_barrier_handle_tasks (state);
if ((bar->generation & 2))
gen = __atomic_load_n (&bar->generation, MEMMODEL_ACQUIRE);
if (__builtin_expect (gen & 1, 0))
{
gomp_barrier_handle_tasks (state);
gen = __atomic_load_n (&bar->generation, MEMMODEL_ACQUIRE);
}
if ((gen & 2) != 0)
generation |= 2;
}
while (bar->generation != state + 4);
while (gen != state + 4);
}
void

15
libgomp/config/linux/bar.h
View File

@ -1,4 +1,4 @@
/* Copyright (C) 2005, 2008, 2009 Free Software Foundation, Inc.
/* Copyright (C) 2005, 2008, 2009, 2011 Free Software Foundation, Inc.
Contributed by Richard Henderson <rth@redhat.com>.
This file is part of the GNU OpenMP Library (libgomp).
@ -50,7 +50,7 @@ static inline void gomp_barrier_init (gomp_barrier_t *bar, unsigned count)
static inline void gomp_barrier_reinit (gomp_barrier_t *bar, unsigned count)
{
__sync_fetch_and_add (&bar->awaited, count - bar->total);
__atomic_add_fetch (&bar->awaited, count - bar->total, MEMMODEL_ACQ_REL);
bar->total = count;
}
@ -69,10 +69,13 @@ extern void gomp_team_barrier_wake (gomp_barrier_t *, int);
static inline gomp_barrier_state_t
gomp_barrier_wait_start (gomp_barrier_t *bar)
{
unsigned int ret = bar->generation & ~3;
/* Do we need any barrier here or is __sync_add_and_fetch acting
as the needed LoadLoad barrier already? */
ret += __sync_add_and_fetch (&bar->awaited, -1) == 0;
unsigned int ret = __atomic_load_n (&bar->generation, MEMMODEL_ACQUIRE) & ~3;
/* A memory barrier is needed before exiting from the various forms
of gomp_barrier_wait, to satisfy OpenMP API version 3.1 section
2.8.6 flush Construct, which says there is an implicit flush during
a barrier region. This is a convenient place to add the barrier,
so we use MEMMODEL_ACQ_REL here rather than MEMMODEL_ACQUIRE. */
ret += __atomic_add_fetch (&bar->awaited, -1, MEMMODEL_ACQ_REL) == 0;
return ret;
}

1
libgomp/task.c
View File

@ -273,6 +273,7 @@ gomp_barrier_handle_tasks (gomp_barrier_state_t state)
gomp_team_barrier_done (&team->barrier, state);
gomp_mutex_unlock (&team->task_lock);
gomp_team_barrier_wake (&team->barrier, 0);
gomp_mutex_lock (&team->task_lock);
}
}
}