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author | Ulrich Drepper <drepper@redhat.com> | 2004-02-19 04:10:16 +0000 |
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committer | Ulrich Drepper <drepper@redhat.com> | 2004-02-19 04:10:16 +0000 |
commit | 37c054c7c4a969816d2bc3c8284bdcadf68ebeec (patch) | |
tree | ec0a8cc53830ddb66445be30615fd15b894495fa /nptl/sysdeps | |
parent | dc39124662b25ce2db28454f1749d67550e4de31 (diff) | |
download | glibc-37c054c7c4a969816d2bc3c8284bdcadf68ebeec.tar.gz glibc-37c054c7c4a969816d2bc3c8284bdcadf68ebeec.tar.xz glibc-37c054c7c4a969816d2bc3c8284bdcadf68ebeec.zip |
Update.
* 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.
Diffstat (limited to 'nptl/sysdeps')
3 files changed, 96 insertions, 36 deletions
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 |