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-rw-r--r--nptl/ChangeLog9
-rw-r--r--nptl/DESIGN-barrier.txt30
-rw-r--r--nptl/Makefile2
-rw-r--r--nptl/sysdeps/pthread/pthread_barrier_wait.c54
-rw-r--r--nptl/sysdeps/unix/sysv/linux/i386/i486/pthread_barrier_wait.S38
-rw-r--r--nptl/sysdeps/unix/sysv/linux/x86_64/pthread_barrier_wait.S40
-rw-r--r--nptl/tst-barrier4.c102
7 files changed, 222 insertions, 53 deletions
diff --git a/nptl/ChangeLog b/nptl/ChangeLog
index 35f37cba88..43107a38c7 100644
--- a/nptl/ChangeLog
+++ b/nptl/ChangeLog
@@ -1,5 +1,14 @@
2004-02-18 Ulrich Drepper <drepper@redhat.com>
+ * sysdeps/unix/sysv/linux/i386/i486/pthread_barrier_wait.S
+ (pthread_barrier_wait): After wakeup, release lock only when the
+ last thread stopped using the barrier object.
+ * sysdeps/unix/sysv/linux/x86_64/pthread_barrier_wait.S
+ (pthread_barrier_wait): Likewise.
+ * sysdeps/pthread/pthread_barrier_wait.c (pthread_barrier_wait):
+ Likewise.
+ * Makefile (tests): Add tst-barrier4.
+ * tst-barrier4.c: New file.
* sysdeps/unix/sysv/linux/i386/i486/pthread_cond_timedwait.S
(__pthread_cond_timedwait): Perform timeout test while holding
diff --git a/nptl/DESIGN-barrier.txt b/nptl/DESIGN-barrier.txt
index 782377f0c5..754e4712e1 100644
--- a/nptl/DESIGN-barrier.txt
+++ b/nptl/DESIGN-barrier.txt
@@ -1,7 +1,7 @@
Barriers pseudocode
===================
- int pthread_barrier_wait(barrier_t * barrier);
+ int pthread_barrier_wait(barrier_t *barrier);
struct barrier_t {
@@ -21,29 +21,27 @@ struct barrier_t {
pthread_barrier_wait(barrier_t *barrier)
{
unsigned int event;
+ result = 0;
lll_lock(barrier->lock);
if (!--barrier->left) {
- barrier->left = barrier->init_count;
barrier->curr_event++;
futex_wake(&barrier->curr_event, INT_MAX)
- lll_unlock(barrier->lock);
-
- return BARRIER_SERIAL_THREAD;
- }
- event = barrier->curr_event;
- for (;;) {
- lll_unlock(barrier->lock);
+ result = BARRIER_SERIAL_THREAD;
+ } else {
+ event = barrier->curr_event;
+ do {
+ lll_unlock(barrier->lock);
- futex_wait(&barrier->curr_event, event)
+ futex_wait(&barrier->curr_event, event)
- lll_lock(barrier->lock);
- if (event != barrier->curr_event)
- break;
+ lll_lock(barrier->lock);
+ } while (event == barrier->curr_event);
}
- lll_unlock(barrier->lock);
- return 0;
-}
+ if (atomic_exchange_and_add (barrier->left, 1) == barrier->init_count - 1)
+ lll_unlock(barrier->lock);
+ return result;
+}
diff --git a/nptl/Makefile b/nptl/Makefile
index 2c020819f1..3cdd1b4c98 100644
--- a/nptl/Makefile
+++ b/nptl/Makefile
@@ -201,7 +201,7 @@ tests = tst-attr1 tst-attr2 tst-attr3 \
tst-key1 tst-key2 tst-key3 tst-key4 \
tst-sem1 tst-sem2 tst-sem3 tst-sem4 tst-sem5 tst-sem6 tst-sem7 \
tst-sem8 tst-sem9 \
- tst-barrier1 tst-barrier2 tst-barrier3 \
+ tst-barrier1 tst-barrier2 tst-barrier3 tst-barrier4 \
tst-align \
tst-basic1 tst-basic2 tst-basic3 tst-basic4 tst-basic5 tst-basic6 \
tst-kill1 tst-kill2 tst-kill3 tst-kill4 tst-kill5 tst-kill6 \
diff --git a/nptl/sysdeps/pthread/pthread_barrier_wait.c b/nptl/sysdeps/pthread/pthread_barrier_wait.c
index 69274d6d64..f6dc3e5f16 100644
--- a/nptl/sysdeps/pthread/pthread_barrier_wait.c
+++ b/nptl/sysdeps/pthread/pthread_barrier_wait.c
@@ -1,4 +1,4 @@
-/* Copyright (C) 2003 Free Software Foundation, Inc.
+/* Copyright (C) 2003, 2004 Free Software Foundation, Inc.
This file is part of the GNU C Library.
Contributed by Martin Schwidefsky <schwidefsky@de.ibm.com>, 2003.
@@ -29,6 +29,7 @@ pthread_barrier_wait (barrier)
pthread_barrier_t *barrier;
{
struct pthread_barrier *ibarrier = (struct pthread_barrier *) barrier;
+ int result = 0;
/* Make sure we are alone. */
lll_lock (ibarrier->lock);
@@ -39,41 +40,42 @@ pthread_barrier_wait (barrier)
/* Are these all? */
if (ibarrier->left == 0)
{
- /* Yes. Restore the barrier to be empty. */
- ibarrier->left = ibarrier->init_count;
-
- /* Increment the event counter to avoid invalid wake-ups and
+ /* Yes. Increment the event counter to avoid invalid wake-ups and
tell the current waiters that it is their turn. */
++ibarrier->curr_event;
/* Wake up everybody. */
lll_futex_wake (&ibarrier->curr_event, INT_MAX);
- /* The barrier is open for business again. */
- lll_unlock (ibarrier->lock);
-
/* This is the thread which finished the serialization. */
- return PTHREAD_BARRIER_SERIAL_THREAD;
+ result = PTHREAD_BARRIER_SERIAL_THREAD;
}
-
- /* The number of the event we are waiting for. The barrier's event
- number must be bumped before we continue. */
- unsigned int event = ibarrier->curr_event;
- do
+ else
{
- /* Before suspending, make the barrier available to others. */
- lll_unlock (ibarrier->lock);
-
- /* Wait for the event counter of the barrier to change. */
- lll_futex_wait (&ibarrier->curr_event, event);
-
- /* We are going to access shared data. */
- lll_lock (ibarrier->lock);
+ /* The number of the event we are waiting for. The barrier's event
+ number must be bumped before we continue. */
+ unsigned int event = ibarrier->curr_event;
+ do
+ {
+ /* Before suspending, make the barrier available to others. */
+ lll_unlock (ibarrier->lock);
+
+ /* Wait for the event counter of the barrier to change. */
+ lll_futex_wait (&ibarrier->curr_event, event);
+
+ /* We are going to access shared data. */
+ lll_lock (ibarrier->lock);
+ }
+ while (event == ibarrier->curr_event);
}
- while (event == ibarrier->curr_event);
- /* We are done, let others use the barrier. */
- lll_unlock (ibarrier->lock);
+ /* Make sure the init_count is stored locally or in a register. */
+ unsigned int init_count = ibarrier->init_count;
+
+ /* If this was the last woken thread, unlock. */
+ if (atomic_exchange_and_add (ibarrier->left, 1) == init_count - 1)
+ /* We are done. */
+ lll_unlock (ibarrier->lock);
- return 0;
+ return result;
}
diff --git a/nptl/sysdeps/unix/sysv/linux/i386/i486/pthread_barrier_wait.S b/nptl/sysdeps/unix/sysv/linux/i386/i486/pthread_barrier_wait.S
index d4b61a10c1..114284c44c 100644
--- a/nptl/sysdeps/unix/sysv/linux/i386/i486/pthread_barrier_wait.S
+++ b/nptl/sysdeps/unix/sysv/linux/i386/i486/pthread_barrier_wait.S
@@ -1,4 +1,4 @@
-/* Copyright (C) 2002, 2003 Free Software Foundation, Inc.
+/* Copyright (C) 2002, 2003, 2004 Free Software Foundation, Inc.
This file is part of the GNU C Library.
Contributed by Ulrich Drepper <drepper@redhat.com>, 2002.
@@ -84,16 +84,32 @@ pthread_barrier_wait:
#endif
je,pn 8b
+ /* Increment LEFT. If this brings the count back to the
+ initial count unlock the object. */
+ movl $1, %edx
+ movl INIT_COUNT(%ebx), %ecx
+ LOCK
+ xaddl %edx, LEFT(%ebx)
+ subl $1, %ecx
+ cmpl %ecx, %edx
+ jne,pt 10f
+
+ /* Release the mutex. We cannot release the lock before
+ waking the waiting threads since otherwise a new thread might
+ arrive and gets waken up, too. */
+ LOCK
+ subl $1, MUTEX(%ebx)
+ jne 9f
+
/* Note: %esi is still zero. */
- movl %esi, %eax /* != PTHREAD_BARRIER_SERIAL_THREAD */
+10: movl %esi, %eax /* != PTHREAD_BARRIER_SERIAL_THREAD */
popl %esi
popl %ebx
ret
/* The necessary number of threads arrived. */
-3: movl INIT_COUNT(%ebx), %eax
- movl %eax, LEFT(%ebx)
+3:
#if CURR_EVENT == 0
addl $1, (%ebx)
#else
@@ -107,6 +123,16 @@ pthread_barrier_wait:
movl $SYS_futex, %eax
ENTER_KERNEL
+ /* Increment LEFT. If this brings the count back to the
+ initial count unlock the object. */
+ movl $1, %edx
+ movl INIT_COUNT(%ebx), %ecx
+ LOCK
+ xaddl %edx, LEFT(%ebx)
+ subl $1, %ecx
+ cmpl %ecx, %edx
+ jne,pt 5f
+
/* Release the mutex. We cannot release the lock before
waking the waiting threads since otherwise a new thread might
arrive and gets waken up, too. */
@@ -130,4 +156,8 @@ pthread_barrier_wait:
6: leal MUTEX(%ebx), %eax
call __lll_mutex_unlock_wake
jmp 7b
+
+9: leal MUTEX(%ebx), %eax
+ call __lll_mutex_unlock_wake
+ jmp 10b
.size pthread_barrier_wait,.-pthread_barrier_wait
diff --git a/nptl/sysdeps/unix/sysv/linux/x86_64/pthread_barrier_wait.S b/nptl/sysdeps/unix/sysv/linux/x86_64/pthread_barrier_wait.S
index 672f2cac0e..e1593f32ff 100644
--- a/nptl/sysdeps/unix/sysv/linux/x86_64/pthread_barrier_wait.S
+++ b/nptl/sysdeps/unix/sysv/linux/x86_64/pthread_barrier_wait.S
@@ -1,4 +1,4 @@
-/* Copyright (C) 2002, 2003 Free Software Foundation, Inc.
+/* Copyright (C) 2002, 2003, 2004 Free Software Foundation, Inc.
This file is part of the GNU C Library.
Contributed by Ulrich Drepper <drepper@redhat.com>, 2002.
@@ -78,14 +78,29 @@ pthread_barrier_wait:
#endif
je 8b
- /* Note: %esi is still zero. */
- movl %esi, %eax /* != PTHREAD_BARRIER_SERIAL_THREAD */
+ /* Increment LEFT. If this brings the count back to the
+ initial count unlock the object. */
+ movl $1, %edx
+ movl INIT_COUNT(%rdi), %eax
+ LOCK
+ xaddl %edx, LEFT(%rdi)
+ subl $1, %eax
+ cmpl %eax, %edx
+ jne,pt 10f
+
+ /* Release the mutex. We cannot release the lock before
+ waking the waiting threads since otherwise a new thread might
+ arrive and gets waken up, too. */
+ LOCK
+ decl MUTEX(%rdi)
+ jne 9f
+
+10: xorl %eax, %eax /* != PTHREAD_BARRIER_SERIAL_THREAD */
retq
/* The necessary number of threads arrived. */
-3: movl INIT_COUNT(%rdi), %eax
- movl %eax, LEFT(%rdi)
+3:
#if CURR_EVENT == 0
incl (%rdi)
#else
@@ -99,6 +114,16 @@ pthread_barrier_wait:
movq $SYS_futex, %rax
syscall
+ /* Increment LEFT. If this brings the count back to the
+ initial count unlock the object. */
+ movl $1, %edx
+ movl INIT_COUNT(%rdi), %eax
+ LOCK
+ xaddl %edx, LEFT(%rdi)
+ subl $1, %eax
+ cmpl %eax, %edx
+ jne,pt 5f
+
/* Release the mutex. We cannot release the lock before
waking the waiting threads since otherwise a new thread might
arrive and gets waken up, too. */
@@ -117,11 +142,14 @@ pthread_barrier_wait:
4: addq $MUTEX, %rdi
callq __lll_mutex_unlock_wake
- subq $MUTEX, %rdi
jmp 5b
6: addq $MUTEX, %rdi
callq __lll_mutex_unlock_wake
subq $MUTEX, %rdi
jmp 7b
+
+9: addq $MUTEX, %rdi
+ callq __lll_mutex_unlock_wake
+ jmp 10b
.size pthread_barrier_wait,.-pthread_barrier_wait
diff --git a/nptl/tst-barrier4.c b/nptl/tst-barrier4.c
new file mode 100644
index 0000000000..a811feefa5
--- /dev/null
+++ b/nptl/tst-barrier4.c
@@ -0,0 +1,102 @@
+/* Copyright (C) 2004 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+ Contributed by Ulrich Drepper <drepper@redhat.com>, 2004.
+
+ 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, write to the Free
+ Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
+ 02111-1307 USA. */
+
+/* This is a test for behavior not guaranteed by POSIX. */
+#include <errno.h>
+#include <pthread.h>
+#include <stdio.h>
+
+
+static pthread_barrier_t b1;
+static pthread_barrier_t b2;
+
+
+#define N 20
+
+static void *
+tf (void *arg)
+{
+ int round = 0;
+
+ while (round++ < 30)
+ {
+ if (pthread_barrier_wait (&b1) == PTHREAD_BARRIER_SERIAL_THREAD)
+ {
+ pthread_barrier_destroy (&b1);
+ if (pthread_barrier_init (&b1, NULL, N) != 0)
+ {
+ puts ("tf: 1st barrier_init failed");
+ exit (1);
+ }
+ }
+
+ if (pthread_barrier_wait (&b2) == PTHREAD_BARRIER_SERIAL_THREAD)
+ {
+ pthread_barrier_destroy (&b2);
+ if (pthread_barrier_init (&b2, NULL, N) != 0)
+ {
+ puts ("tf: 2nd barrier_init failed");
+ exit (1);
+ }
+ }
+ }
+
+ return NULL;
+}
+
+
+static int
+do_test (void)
+{
+ int cnt;
+
+ if (pthread_barrier_init (&b1, NULL, N) != 0)
+ {
+ puts ("1st barrier_init failed");
+ return 1;
+ }
+
+ if (pthread_barrier_init (&b2, NULL, N) != 0)
+ {
+ puts ("2nd barrier_init failed");
+ return 1;
+ }
+
+ pthread_t th[N - 1];
+ for (cnt = 0; cnt < N - 1; ++cnt)
+ if (pthread_create (&th[cnt], NULL, tf, NULL) != 0)
+ {
+ puts ("pthread_create failed");
+ return 1;
+ }
+
+ tf (NULL);
+
+ for (cnt = 0; cnt < N - 1; ++cnt)
+ if (pthread_join (th[cnt], NULL) != 0)
+ {
+ puts ("pthread_join failed");
+ return 1;
+ }
+
+ return 0;
+}
+
+#define TEST_FUNCTION do_test ()
+#include "../test-skeleton.c"
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