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New pthread_barrier algorithm to fulfill barrier destruction requirements. 

The previous barrier implementation did not fulfill the POSIX requirements
for when a barrier can be destroyed.  Specifically, it was possible that
threads that haven't noticed yet that their round is complete still access
the barrier's memory, and that those accesses can happen after the barrier
has been legally destroyed.
The new algorithm does not have this issue, and it avoids using a lock
internally.
This commit is contained in:
Torvald Riegel 2015-06-24 14:37:32 +02:00
parent a3e5b4feeb
commit b02840bacd
18 changed files with 417 additions and 762 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

27
ChangeLog
View File

@ -1,3 +1,30 @@
2016-01-15 Torvald Riegel <triegel@redhat.com>
[BZ #13065]
* nptl/pthread_barrier_wait.c (__pthread_barrier_wait): Replace with
new implementation.
* nptl/pthread_barrier_destroy.c (pthread_barrier_destroy): Likewise.
* nptl/pthread_barrier_init.c (__pthread_barrier_init): Adapt.
* sysdeps/nptl/internaltypes.h (pthread_barrier): Adapt.
(BARRIER_IN_THRESHOLD): New macro.
* nptl/pthread_barrierattr_setpshared.c
(pthread_barrierattr_setpshared): Clean up.
* nptl/tst-barrier4.c: Correct comment.
* nptl/tst-barrier5.c: New file.
* nptl/Makefile (tests): Add nptl/tst-barrier5.c.
(gen-as-const-headers): Remove lowlevelbarrier.sym.
* sysdeps/unix/sysv/linux/i386/pthread_barrier_wait.S: Remove.
* sysdeps/unix/sysv/linux/x86_64/pthread_barrier_wait.S: Remove.
* nptl/lowlevelbarrier.sym: Remove.
* nptl/DESIGN-barrier.txt: Remove.
* sysdeps/sparc/nptl/pthread_barrier_destroy.c: Remove.
* sysdeps/sparc/nptl/pthread_barrier_init.c: Remove.
* sysdeps/sparc/nptl/pthread_barrier_wait.c: Remove.
* sysdeps/sparc/sparc32/pthread_barrier_wait.c: Replace with build
error.
* sysdeps/sparc/sparc32/sparcv9/pthread_barrier_wait.c: Use generic
implementation.
2016-01-15 Paul E. Murphy <murphyp@linux.vnet.ibm.com>
* rt/tst-mqueue5.c (thr): Cleanup misleading comment.

44
nptl/DESIGN-barrier.txt
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@ -1,44 +0,0 @@
Barriers pseudocode
===================
int pthread_barrier_wait(barrier_t *barrier);
struct barrier_t {
unsigned int lock:
- internal mutex
unsigned int left;
- current barrier count, # of threads still needed.
unsigned int init_count;
- number of threads needed for the barrier to continue.
unsigned int curr_event;
- generation count
}
pthread_barrier_wait(barrier_t *barrier)
{
unsigned int event;
result = 0;
lll_lock(barrier->lock);
if (!--barrier->left) {
barrier->curr_event++;
futex_wake(&barrier->curr_event, INT_MAX)
result = BARRIER_SERIAL_THREAD;
} else {
event = barrier->curr_event;
lll_unlock(barrier->lock);
do {
futex_wait(&barrier->curr_event, event)
} while (event == barrier->curr_event);
}
if (atomic_increment_val (barrier->left) == barrier->init_count)
lll_unlock(barrier->lock);
return result;
}

4
nptl/Makefile
View File

@ -241,7 +241,7 @@ tests = tst-typesizes \
tst-sem1 tst-sem2 tst-sem3 tst-sem4 tst-sem5 tst-sem6 tst-sem7 \
tst-sem8 tst-sem9 tst-sem10 tst-sem11 tst-sem12 tst-sem13 tst-sem14 \
tst-sem15 \
tst-barrier1 tst-barrier2 tst-barrier3 tst-barrier4 \
tst-barrier1 tst-barrier2 tst-barrier3 tst-barrier4 tst-barrier5 \
tst-align tst-align3 \
tst-basic1 tst-basic2 tst-basic3 tst-basic4 tst-basic5 tst-basic6 \
tst-basic7 \
@ -302,7 +302,7 @@ tests-nolibpthread = tst-unload
gen-as-const-headers = pthread-errnos.sym \
lowlevelcond.sym lowlevelrwlock.sym \
lowlevelbarrier.sym unwindbuf.sym \
unwindbuf.sym \
lowlevelrobustlock.sym pthread-pi-defines.sym

12
nptl/lowlevelbarrier.sym
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@ -1,12 +0,0 @@
#include <stddef.h>
#include <sched.h>
#include <bits/pthreadtypes.h>
#include "internaltypes.h"
--
CURR_EVENT offsetof (struct pthread_barrier, curr_event)
MUTEX offsetof (struct pthread_barrier, lock)
LEFT offsetof (struct pthread_barrier, left)
INIT_COUNT offsetof (struct pthread_barrier, init_count)
PRIVATE offsetof (struct pthread_barrier, private)

47
nptl/pthread_barrier_destroy.c
View File

@ -18,25 +18,44 @@
#include <errno.h>
#include "pthreadP.h"
#include <lowlevellock.h>
#include <atomic.h>
#include <futex-internal.h>
int
pthread_barrier_destroy (pthread_barrier_t *barrier)
{
struct pthread_barrier *ibarrier;
int result = EBUSY;
struct pthread_barrier *bar = (struct pthread_barrier *) barrier;
ibarrier = (struct pthread_barrier *) barrier;
/* Destroying a barrier is only allowed if no thread is blocked on it.
Thus, there is no unfinished round, and all modifications to IN will
have happened before us (either because the calling thread took part
in the most recent round and thus synchronized-with all other threads
entering, or the program ensured this through other synchronization).
We must wait until all threads that entered so far have confirmed that
they have exited as well. To get the notification, pretend that we have
reached the reset threshold. */
unsigned int count = bar->count;
unsigned int max_in_before_reset = BARRIER_IN_THRESHOLD
- BARRIER_IN_THRESHOLD % count;
/* Relaxed MO sufficient because the program must have ensured that all
modifications happen-before this load (see above). */
unsigned int in = atomic_load_relaxed (&bar->in);
/* Trigger reset. The required acquire MO is below. */
if (atomic_fetch_add_relaxed (&bar->out, max_in_before_reset - in) < in)
{
/* Not all threads confirmed yet that they have exited, so another
thread will perform a reset. Wait until that has happened. */
while (in != 0)
{
futex_wait_simple (&bar->in, in, bar->shared);
in = atomic_load_relaxed (&bar->in);
}
}
/* We must ensure that memory reuse happens after all prior use of the
barrier (specifically, synchronize-with the reset of the barrier or the
confirmation of threads leaving the barrier). */
atomic_thread_fence_acquire ();
lll_lock (ibarrier->lock, ibarrier->private ^ FUTEX_PRIVATE_FLAG);
if (__glibc_likely (ibarrier->left == ibarrier->init_count))
/* The barrier is not used anymore. */
result = 0;
else
/* Still used, return with an error. */
lll_unlock (ibarrier->lock, ibarrier->private ^ FUTEX_PRIVATE_FLAG);
return result;
return 0;
}

23
nptl/pthread_barrier_init.c
View File

@ -18,7 +18,7 @@
#include <errno.h>
#include "pthreadP.h"
#include <lowlevellock.h>
#include <futex-internal.h>
#include <kernel-features.h>
@ -34,8 +34,10 @@ __pthread_barrier_init (pthread_barrier_t *barrier,
{
struct pthread_barrier *ibarrier;
/* XXX EINVAL is not specified by POSIX as a possible error code. */
if (__glibc_unlikely (count == 0))
/* XXX EINVAL is not specified by POSIX as a possible error code for COUNT
being too large. See pthread_barrier_wait for the reason for the
comparison with BARRIER_IN_THRESHOLD. */
if (__glibc_unlikely (count == 0 || count >= BARRIER_IN_THRESHOLD))
return EINVAL;
const struct pthread_barrierattr *iattr
@ -46,15 +48,12 @@ __pthread_barrier_init (pthread_barrier_t *barrier,
ibarrier = (struct pthread_barrier *) barrier;
/* Initialize the individual fields. */
ibarrier->lock = LLL_LOCK_INITIALIZER;
ibarrier->left = count;
ibarrier->init_count = count;
ibarrier->curr_event = 0;
/* XXX Don't use FUTEX_SHARED or FUTEX_PRIVATE as long as there are still
assembly implementations that expect the value determined below. */
ibarrier->private = (iattr->pshared != PTHREAD_PROCESS_PRIVATE
? 0 : FUTEX_PRIVATE_FLAG);
ibarrier->in = 0;
ibarrier->out = 0;
ibarrier->count = count;
ibarrier->current_round = 0;
ibarrier->shared = (iattr->pshared == PTHREAD_PROCESS_PRIVATE
? FUTEX_PRIVATE : FUTEX_SHARED);
return 0;
}

229
nptl/pthread_barrier_wait.c
View File

@ -18,63 +18,206 @@
#include <errno.h>
#include <sysdep.h>
#include <lowlevellock.h>
#include <futex-internal.h>
#include <pthreadP.h>
/* Wait on barrier. */
/* Wait on the barrier.
In each round, we wait for a fixed number of threads to enter the barrier
(COUNT). Once that has happened, exactly these threads are allowed to
leave the barrier. Note that POSIX does not require that only COUNT
threads can attempt to block using the barrier concurrently.
We count the number of threads that have entered (IN). Each thread
increments IN when entering, thus getting a position in the sequence of
threads that are or have been waiting (starting with 1, so the position
is the number of threads that have entered so far including the current
thread).
CURRENT_ROUND designates the most recent thread whose round has been
detected as complete. When a thread detects that enough threads have
entered to make a round complete, it finishes this round by effectively
adding COUNT to CURRENT_ROUND atomically. Threads that believe that their
round is not complete yet wait until CURRENT_ROUND is not smaller than
their position anymore.
A barrier can be destroyed as soon as no threads are blocked on the
barrier. This is already the case if just one thread from the last round
has stopped waiting and returned to the caller; the assumption is that
all threads from the round are unblocked atomically, even though they may
return at different times from the respective calls to
pthread_barrier_wait). Thus, a valid call to pthread_barrier_destroy can
be concurrent with other threads still figuring out that their round has
been completed. Therefore, threads need to confirm that they have left
the barrier by incrementing OUT, and pthread_barrier_destroy needs to wait
until OUT equals IN.
To avoid an ABA issue for futex_wait on CURRENT_ROUND and for archs with
32b-only atomics, we additionally reset the barrier when IN reaches
a threshold to avoid overflow. We assume that the total number of threads
is less than UINT_MAX/2, and set the threshold accordingly so that we can
use a simple atomic_fetch_add on IN instead of a CAS when entering. The
threshold is always set to the end of a round, so all threads that have
entered are either pre-reset threads or post-reset threads (i.e., have a
position larger than the threshold).
Pre-reset threads just run the algorithm explained above. Post-reset
threads wait until IN is reset to a pre-threshold value.
When the last pre-reset thread leaves the barrier (i.e., OUT equals the
threshold), it resets the barrier to its initial state. Other (post-reset)
threads wait for the reset to have finished by waiting until IN is less
than the threshold and then restart by trying to enter the barrier again.
We reuse the reset mechanism in pthread_barrier_destroy to get notified
when all threads have left the barrier: We trigger an artificial reset and
wait for the last pre-reset thread to finish reset, thus notifying the
thread that is about to destroy the barrier.
Blocking using futexes is straightforward: pre-reset threads wait for
completion of their round using CURRENT_ROUND as futex word, and post-reset
threads and pthread_barrier_destroy use IN as futex word.
Further notes:
* It is not simple to let some of the post-reset threads help with the
reset because of the ABA issues that arise; therefore, we simply make
the last thread to leave responsible for the reset.
* POSIX leaves it unspecified whether a signal handler running in a thread
that has been unblocked (because its round is complete) can stall all
other threads and prevent them from returning from the barrier. In this
implementation, other threads will return. However,
pthread_barrier_destroy will of course wait for the signal handler thread
to confirm that it left the barrier.
TODO We should add spinning with back-off. Once we do that, we could also
try to avoid the futex_wake syscall when a round is detected as finished.
If we do not spin, it is quite likely that at least some other threads will
have called futex_wait already. */
int
__pthread_barrier_wait (pthread_barrier_t *barrier)
{
struct pthread_barrier *ibarrier = (struct pthread_barrier *) barrier;
int result = 0;
int lll_private = ibarrier->private ^ FUTEX_PRIVATE_FLAG;
int futex_private = (lll_private == LLL_PRIVATE
? FUTEX_PRIVATE : FUTEX_SHARED);
struct pthread_barrier *bar = (struct pthread_barrier *) barrier;
/* Make sure we are alone. */
lll_lock (ibarrier->lock, lll_private);
/* How many threads entered so far, including ourself. */
unsigned int i;
/* One more arrival. */
--ibarrier->left;
reset_restart:
/* Try to enter the barrier. We need acquire MO to (1) ensure that if we
observe that our round can be completed (see below for our attempt to do
so), all pre-barrier-entry effects of all threads in our round happen
before us completing the round, and (2) to make our use of the barrier
happen after a potential reset. We need release MO to make sure that our
pre-barrier-entry effects happen before threads in this round leaving the
barrier. */
i = atomic_fetch_add_acq_rel (&bar->in, 1) + 1;
/* These loads are after the fetch_add so that we're less likely to first
pull in the cache line as shared. */
unsigned int count = bar->count;
/* This is the number of threads that can enter before we need to reset.
Always at the end of a round. */
unsigned int max_in_before_reset = BARRIER_IN_THRESHOLD
- BARRIER_IN_THRESHOLD % count;
/* Are these all? */
if (ibarrier->left == 0)
if (i > max_in_before_reset)
{
/* 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. */
futex_wake (&ibarrier->curr_event, INT_MAX, futex_private);
/* This is the thread which finished the serialization. */
result = PTHREAD_BARRIER_SERIAL_THREAD;
}
else
{
/* 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;
/* Before suspending, make the barrier available to others. */
lll_unlock (ibarrier->lock, lll_private);
/* Wait for the event counter of the barrier to change. */
do
futex_wait_simple (&ibarrier->curr_event, event, futex_private);
while (event == ibarrier->curr_event);
/* We're in a reset round. Just wait for a reset to finish; do not
help finishing previous rounds because this could happen
concurrently with a reset. */
while (i > max_in_before_reset)
{
futex_wait_simple (&bar->in, i, bar->shared);
/* Relaxed MO is fine here because we just need an indication for
when we should retry to enter (which will use acquire MO, see
above). */
i = atomic_load_relaxed (&bar->in);
}
goto reset_restart;
}
/* Make sure the init_count is stored locally or in a register. */
unsigned int init_count = ibarrier->init_count;
/* Look at the current round. At this point, we are just interested in
whether we can complete rounds, based on the information we obtained
through our acquire-MO load of IN. Nonetheless, if we notice that
our round has been completed using this load, we use the acquire-MO
fence below to make sure that all pre-barrier-entry effects of all
threads in our round happen before us leaving the barrier. Therefore,
relaxed MO is sufficient. */
unsigned cr = atomic_load_relaxed (&bar->current_round);
/* If this was the last woken thread, unlock. */
if (atomic_increment_val (&ibarrier->left) == init_count)
/* We are done. */
lll_unlock (ibarrier->lock, lll_private);
/* Try to finish previous rounds and/or the current round. We simply
consider just our position here and do not try to do the work of threads
that entered more recently. */
while (cr + count <= i)
{
/* Calculate the new current round based on how many threads entered.
NEWCR must be larger than CR because CR+COUNT ends a round. */
unsigned int newcr = i - i % count;
/* Try to complete previous and/or the current round. We need release
MO to propagate the happens-before that we observed through reading
with acquire MO from IN to other threads. If the CAS fails, it
is like the relaxed-MO load of CURRENT_ROUND above. */
if (atomic_compare_exchange_weak_release (&bar->current_round, &cr,
newcr))
{
/* Update CR with the modification we just did. */
cr = newcr;
/* Wake threads belonging to the rounds we just finished. We may
wake more threads than necessary if more than COUNT threads try
to block concurrently on the barrier, but this is not a typical
use of barriers.
Note that we can still access SHARED because we haven't yet
confirmed to have left the barrier. */
futex_wake (&bar->current_round, INT_MAX, bar->shared);
/* We did as much as we could based on our position. If we advanced
the current round to a round sufficient for us, do not wait for
that to happen and skip the acquire fence (we already
synchronize-with all other threads in our round through the
initial acquire MO fetch_add of IN. */
if (i <= cr)
goto ready_to_leave;
else
break;
}
}
return result;
/* Wait until the current round is more recent than the round we are in. */
while (i > cr)
{
/* Wait for the current round to finish. */
futex_wait_simple (&bar->current_round, cr, bar->shared);
/* See the fence below. */
cr = atomic_load_relaxed (&bar->current_round);
}
/* Our round finished. Use the acquire MO fence to synchronize-with the
thread that finished the round, either through the initial load of
CURRENT_ROUND above or a failed CAS in the loop above. */
atomic_thread_fence_acquire ();
/* Now signal that we left. */
unsigned int o;
ready_to_leave:
/* We need release MO here so that our use of the barrier happens before
reset or memory reuse after pthread_barrier_destroy. */
o = atomic_fetch_add_release (&bar->out, 1) + 1;
if (o == max_in_before_reset)
{
/* Perform a reset if we are the last pre-reset thread leaving. All
other threads accessing the barrier are post-reset threads and are
incrementing or spinning on IN. Thus, resetting IN as the last step
of reset ensures that the reset is not concurrent with actual use of
the barrier. We need the acquire MO fence so that the reset happens
after use of the barrier by all earlier pre-reset threads. */
atomic_thread_fence_acquire ();
atomic_store_relaxed (&bar->current_round, 0);
atomic_store_relaxed (&bar->out, 0);
/* When destroying the barrier, we wait for a reset to happen. Thus,
we must load SHARED now so that this happens before the barrier is
destroyed. */
int shared = bar->shared;
atomic_store_release (&bar->in, 0);
futex_wake (&bar->in, INT_MAX, shared);
}
/* Return a special value for exactly one thread per round. */
return i % count == 0 ? PTHREAD_BARRIER_SERIAL_THREAD : 0;
}
weak_alias (__pthread_barrier_wait, pthread_barrier_wait)

6
nptl/pthread_barrierattr_setpshared.c
View File

@ -24,15 +24,11 @@
int
pthread_barrierattr_setpshared (pthread_barrierattr_t *attr, int pshared)
{
struct pthread_barrierattr *iattr;
int err = futex_supports_pshared (pshared);
if (err != 0)
return err;
iattr = (struct pthread_barrierattr *) attr;
iattr->pshared = pshared;
((struct pthread_barrierattr *) attr)->pshared = pshared;
return 0;
}

2
nptl/tst-barrier4.c
View File

@ -16,7 +16,7 @@
License along with the GNU C Library; if not, see
<http://www.gnu.org/licenses/>. */
/* This is a test for behavior not guaranteed by POSIX. */
/* This tests destruction of a barrier right after waiting on it. */
#include <errno.h>
#include <pthread.h>
#include <stdio.h>

145
nptl/tst-barrier5.c Normal file
View File

@ -0,0 +1,145 @@
/* Copyright (C) 2004-2015 Free Software Foundation, Inc.
This file is part of the GNU C Library.
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/>. */
/* This tests the barrier reset mechanism. */
#include <errno.h>
#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>
#include <internaltypes.h>
static pthread_barrier_t b1;
static pthread_barrier_t b2;
#define N 20
#define ROUNDS_PER_RUN 20
#define START ((BARRIER_IN_THRESHOLD / N - ROUNDS_PER_RUN / 2) * N)
static void *
tf (void *arg)
{
int runs = 0;
while (runs++ < 30)
{
/* In each run, we execute a number of rounds and initialize the barrier
so that we will go over the reset threshold with those rounds. */
for (int rounds = 0; rounds < ROUNDS_PER_RUN; rounds++)
pthread_barrier_wait (&b1);
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);
}
puts ("b1 reinitialized");
/* Trigger a reset. */
struct pthread_barrier *bar = (struct pthread_barrier *) &b1;
bar->in = START;
bar->out = START;
/* We deliberately don't set bar->current_round so that we also
test whether the helping for the updates of current_round
works correctly. */
}
/* Same as above, just for b2. */
for (int rounds = 0; rounds < ROUNDS_PER_RUN; rounds++)
pthread_barrier_wait (&b2);
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);
}
puts ("b2 reinitialized");
/* Trigger a reset. See above. */
struct pthread_barrier *bar = (struct pthread_barrier *) &b2;
bar->in = START;
bar->out = START;
}
}
return NULL;
}
static int
do_test (void)
{
pthread_attr_t at;
int cnt;
if (pthread_attr_init (&at) != 0)
{
puts ("attr_init failed");
return 1;
}
if (pthread_attr_setstacksize (&at, 1 * 1024 * 1024) != 0)
{
puts ("attr_setstacksize failed");
return 1;
}
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], &at, tf, NULL) != 0)
{
puts ("pthread_create failed");
return 1;
}
if (pthread_attr_destroy (&at) != 0)
{
puts ("attr_destroy 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"

15
sysdeps/nptl/internaltypes.h
View File

@ -92,15 +92,18 @@ struct pthread_rwlockattr
};
/* Barrier data structure. */
/* Barrier data structure. See pthread_barrier_wait for a description
of how these fields are used. */
struct pthread_barrier
{
unsigned int curr_event;
int lock;
unsigned int left;
unsigned int init_count;
int private;
unsigned int in;
unsigned int current_round;
unsigned int count;
int shared;
unsigned int out;
};
/* See pthread_barrier_wait for a description. */
#define BARRIER_IN_THRESHOLD (UINT_MAX/2)
/* Barrier variable attribute data structure. */

44
sysdeps/sparc/nptl/pthread_barrier_destroy.c
View File

@ -1,44 +0,0 @@
/* Copyright (C) 2002-2016 Free Software Foundation, Inc.
This file is part of the GNU C Library.
Contributed by Ulrich Drepper <drepper@redhat.com>, 2002.
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 <errno.h>
#include "pthreadP.h"
#include <lowlevellock.h>
#include <sparc-nptl.h>
int
pthread_barrier_destroy (pthread_barrier_t *barrier)
{
union sparc_pthread_barrier *ibarrier;
int result = EBUSY;
ibarrier = (union sparc_pthread_barrier *) barrier;
int private = ibarrier->s.pshared ? LLL_SHARED : LLL_PRIVATE;
lll_lock (ibarrier->b.lock, private);
if (__glibc_likely (ibarrier->b.left == ibarrier->b.init_count))
/* The barrier is not used anymore. */
result = 0;
else
/* Still used, return with an error. */
lll_unlock (ibarrier->b.lock, private);
return result;
}

54
sysdeps/sparc/nptl/pthread_barrier_init.c
View File

@ -1,54 +0,0 @@
/* Copyright (C) 2002-2016 Free Software Foundation, Inc.
This file is part of the GNU C Library.
Contributed by Ulrich Drepper <drepper@redhat.com>, 2002.
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 <errno.h>
#include "pthreadP.h"
#include <lowlevellock.h>
#include <futex-internal.h>
#include <sparc-nptl.h>
int
__pthread_barrier_init (pthread_barrier_t *barrier,
const pthread_barrierattr_t *attr, unsigned int count)
{
union sparc_pthread_barrier *ibarrier;
if (__glibc_unlikely (count == 0))
return EINVAL;
struct pthread_barrierattr *iattr = (struct pthread_barrierattr *) attr;
if (iattr != NULL)
{
int err = futex_supports_pshared (iattr->pshared);
if (err != 0)
return err;
}
ibarrier = (union sparc_pthread_barrier *) barrier;
/* Initialize the individual fields. */
ibarrier->b.lock = LLL_LOCK_INITIALIZER;
ibarrier->b.left = count;
ibarrier->b.init_count = count;
ibarrier->b.curr_event = 0;
ibarrier->s.left_lock = 0;
ibarrier->s.pshared = (iattr && iattr->pshared == PTHREAD_PROCESS_SHARED);
return 0;
}
weak_alias (__pthread_barrier_init, pthread_barrier_init)

80
sysdeps/sparc/nptl/pthread_barrier_wait.c
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@ -1,80 +0,0 @@
/* Copyright (C) 2003-2016 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 <errno.h>
#include <sysdep.h>
#include <lowlevellock.h>
#include <pthreadP.h>
#include <sparc-nptl.h>
#include <futex-internal.h>
/* Wait on barrier. */
int
__pthread_barrier_wait (pthread_barrier_t *barrier)
{
union sparc_pthread_barrier *ibarrier
= (union sparc_pthread_barrier *) barrier;
int result = 0;
int private = ibarrier->s.pshared ? LLL_SHARED : LLL_PRIVATE;
int futex_private = ibarrier->s.pshared ? FUTEX_SHARED : FUTEX_PRIVATE;
/* Make sure we are alone. */
lll_lock (ibarrier->b.lock, private);
/* One more arrival. */
--ibarrier->b.left;
/* Are these all? */
if (ibarrier->b.left == 0)
{
/* Yes. Increment the event counter to avoid invalid wake-ups and
tell the current waiters that it is their turn. */
++ibarrier->b.curr_event;
/* Wake up everybody. */
futex_wake (&ibarrier->b.curr_event, INT_MAX, futex_private);
/* This is the thread which finished the serialization. */
result = PTHREAD_BARRIER_SERIAL_THREAD;
}
else
{
/* The number of the event we are waiting for. The barrier's event
number must be bumped before we continue. */
unsigned int event = ibarrier->b.curr_event;
/* Before suspending, make the barrier available to others. */
lll_unlock (ibarrier->b.lock, private);
/* Wait for the event counter of the barrier to change. */
do
futex_wait_simple (&ibarrier->b.curr_event, event, futex_private);
while (event == ibarrier->b.curr_event);
}
/* Make sure the init_count is stored locally or in a register. */
unsigned int init_count = ibarrier->b.init_count;
/* If this was the last woken thread, unlock. */
if (atomic_increment_val (&ibarrier->b.left) == init_count)
/* We are done. */
lll_unlock (ibarrier->b.lock, private);
return result;
}
weak_alias (__pthread_barrier_wait, pthread_barrier_wait)

97
sysdeps/sparc/sparc32/pthread_barrier_wait.c
View File

@ -1,96 +1 @@
/* Copyright (C) 2003-2016 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 <errno.h>
#include <sysdep.h>
#include <lowlevellock.h>
#include <pthreadP.h>
#include <sparc-nptl.h>
#include <futex-internal.h>
/* Wait on barrier. */
int
__pthread_barrier_wait (pthread_barrier_t *barrier)
{
union sparc_pthread_barrier *ibarrier
= (union sparc_pthread_barrier *) barrier;
int result = 0;
int private = ibarrier->s.pshared ? LLL_SHARED : LLL_PRIVATE;
int futex_private = ibarrier->s.pshared ? FUTEX_SHARED : FUTEX_PRIVATE;
/* Make sure we are alone. */
lll_lock (ibarrier->b.lock, private);
/* One more arrival. */
--ibarrier->b.left;
/* Are these all? */
if (ibarrier->b.left == 0)
{
/* Yes. Increment the event counter to avoid invalid wake-ups and
tell the current waiters that it is their turn. */
++ibarrier->b.curr_event;
/* Wake up everybody. */
futex_wake (&ibarrier->b.curr_event, INT_MAX, futex_private);
/* This is the thread which finished the serialization. */
result = PTHREAD_BARRIER_SERIAL_THREAD;
}
else
{
/* The number of the event we are waiting for. The barrier's event
number must be bumped before we continue. */
unsigned int event = ibarrier->b.curr_event;
/* Before suspending, make the barrier available to others. */
lll_unlock (ibarrier->b.lock, private);
/* Wait for the event counter of the barrier to change. */
do
futex_wait_simple (&ibarrier->b.curr_event, event, futex_private);
while (event == ibarrier->b.curr_event);
}
/* Make sure the init_count is stored locally or in a register. */
unsigned int init_count = ibarrier->b.init_count;
/* If this was the last woken thread, unlock. */
if (__atomic_is_v9 || ibarrier->s.pshared == 0)
{
if (atomic_increment_val (&ibarrier->b.left) == init_count)
/* We are done. */
lll_unlock (ibarrier->b.lock, private);
}
else
{
unsigned int left;
/* Slightly more complicated. On pre-v9 CPUs, atomic_increment_val
is only atomic for threads within the same process, not for
multiple processes. */
__sparc32_atomic_do_lock24 (&ibarrier->s.left_lock);
left = ++ibarrier->b.left;
__sparc32_atomic_do_unlock24 (&ibarrier->s.left_lock);
if (left == init_count)
/* We are done. */
lll_unlock (ibarrier->b.lock, private);
}
return result;
}
weak_alias (__pthread_barrier_wait, pthread_barrier_wait)
#error No support for pthread barriers on pre-v9 sparc.

2
sysdeps/sparc/sparc32/sparcv9/pthread_barrier_wait.c
View File

@ -1 +1 @@
#include <sysdeps/sparc/nptl/pthread_barrier_wait.c>
#include <nptl/pthread_barrier_wait.c>

187
sysdeps/unix/sysv/linux/i386/pthread_barrier_wait.S
View File

@ -1,187 +0,0 @@
/* Copyright (C) 2002-2016 Free Software Foundation, Inc.
This file is part of the GNU C Library.
Contributed by Ulrich Drepper <drepper@redhat.com>, 2002.
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 <sysdep.h>
#include <lowlevellock.h>
#include <lowlevelbarrier.h>
.text
.globl __pthread_barrier_wait
.type __pthread_barrier_wait,@function
.align 16
__pthread_barrier_wait:
cfi_startproc
pushl %ebx
cfi_adjust_cfa_offset(4)
cfi_offset(%ebx, -8)
movl 8(%esp), %ebx
/* Get the mutex. */
movl $1, %edx
xorl %eax, %eax
LOCK
cmpxchgl %edx, MUTEX(%ebx)
jnz 1f
/* One less waiter. If this was the last one needed wake
everybody. */
2: subl $1, LEFT(%ebx)
je 3f
/* There are more threads to come. */
pushl %esi
cfi_adjust_cfa_offset(4)
cfi_offset(%esi, -12)
#if CURR_EVENT == 0
movl (%ebx), %edx
#else
movl CURR_EVENT(%ebx), %edx
#endif
/* Release the mutex. */
LOCK
subl $1, MUTEX(%ebx)
jne 6f
/* Wait for the remaining threads. The call will return immediately
if the CURR_EVENT memory has meanwhile been changed. */
7:
#if FUTEX_WAIT == 0
movl PRIVATE(%ebx), %ecx
#else
movl $FUTEX_WAIT, %ecx
orl PRIVATE(%ebx), %ecx
#endif
xorl %esi, %esi
8: movl $SYS_futex, %eax
ENTER_KERNEL
/* Don't return on spurious wakeups. The syscall does not change
any register except %eax so there is no need to reload any of
them. */
#if CURR_EVENT == 0
cmpl %edx, (%ebx)
#else
cmpl %edx, CURR_EVENT(%ebx)
#endif
je 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 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. */
10: movl %esi, %eax /* != PTHREAD_BARRIER_SERIAL_THREAD */
popl %esi
cfi_adjust_cfa_offset(-4)
cfi_restore(%esi)
popl %ebx
cfi_adjust_cfa_offset(-4)
cfi_restore(%ebx)
ret
cfi_adjust_cfa_offset(4)
cfi_offset(%ebx, -8)
/* The necessary number of threads arrived. */
3:
#if CURR_EVENT == 0
addl $1, (%ebx)
#else
addl $1, CURR_EVENT(%ebx)
#endif
/* Wake up all waiters. The count is a signed number in the kernel
so 0x7fffffff is the highest value. */
movl $0x7fffffff, %edx
movl $FUTEX_WAKE, %ecx
orl PRIVATE(%ebx), %ecx
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 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. */
LOCK
subl $1, MUTEX(%ebx)
jne 4f
5: orl $-1, %eax /* == PTHREAD_BARRIER_SERIAL_THREAD */
popl %ebx
cfi_adjust_cfa_offset(-4)
cfi_restore(%ebx)
ret
cfi_adjust_cfa_offset(4)
cfi_offset(%ebx, -8)
1: movl PRIVATE(%ebx), %ecx
leal MUTEX(%ebx), %edx
xorl $LLL_SHARED, %ecx
call __lll_lock_wait
jmp 2b
4: movl PRIVATE(%ebx), %ecx
leal MUTEX(%ebx), %eax
xorl $LLL_SHARED, %ecx
call __lll_unlock_wake
jmp 5b
cfi_adjust_cfa_offset(4)
cfi_offset(%esi, -12)
6: movl PRIVATE(%ebx), %ecx
leal MUTEX(%ebx), %eax
xorl $LLL_SHARED, %ecx
call __lll_unlock_wake
jmp 7b
9: movl PRIVATE(%ebx), %ecx
leal MUTEX(%ebx), %eax
xorl $LLL_SHARED, %ecx
call __lll_unlock_wake
jmp 10b
cfi_endproc
.size __pthread_barrier_wait,.-__pthread_barrier_wait
weak_alias (__pthread_barrier_wait, pthread_barrier_wait)

161
sysdeps/unix/sysv/linux/x86_64/pthread_barrier_wait.S
View File

@ -1,161 +0,0 @@
/* Copyright (C) 2002-2016 Free Software Foundation, Inc.
This file is part of the GNU C Library.
Contributed by Ulrich Drepper <drepper@redhat.com>, 2002.
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 <sysdep.h>
#include <lowlevellock.h>
#include <lowlevelbarrier.h>
.text
.globl __pthread_barrier_wait
.type __pthread_barrier_wait,@function
.align 16
__pthread_barrier_wait:
/* Get the mutex. */
xorl %eax, %eax
movl $1, %esi
LOCK
cmpxchgl %esi, MUTEX(%rdi)
jnz 1f
/* One less waiter. If this was the last one needed wake
everybody. */
2: decl LEFT(%rdi)
je 3f
/* There are more threads to come. */
#if CURR_EVENT == 0
movl (%rdi), %edx
#else
movl CURR_EVENT(%rdi), %edx
#endif
/* Release the mutex. */
LOCK
decl MUTEX(%rdi)
jne 6f
/* Wait for the remaining threads. The call will return immediately
if the CURR_EVENT memory has meanwhile been changed. */
7:
#if FUTEX_WAIT == 0
movl PRIVATE(%rdi), %esi
#else
movl $FUTEX_WAIT, %esi
orl PRIVATE(%rdi), %esi
#endif
xorq %r10, %r10
8: movl $SYS_futex, %eax
syscall
/* Don't return on spurious wakeups. The syscall does not change
any register except %eax so there is no need to reload any of
them. */
#if CURR_EVENT == 0
cmpl %edx, (%rdi)
#else
cmpl %edx, CURR_EVENT(%rdi)
#endif
je 8b
/* 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:
#if CURR_EVENT == 0
incl (%rdi)
#else
incl CURR_EVENT(%rdi)
#endif
/* Wake up all waiters. The count is a signed number in the kernel
so 0x7fffffff is the highest value. */
movl $0x7fffffff, %edx
movl $FUTEX_WAKE, %esi
orl PRIVATE(%rdi), %esi
movl $SYS_futex, %eax
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. */
LOCK
decl MUTEX(%rdi)
jne 4f
5: orl $-1, %eax /* == PTHREAD_BARRIER_SERIAL_THREAD */
retq
1: movl PRIVATE(%rdi), %esi
addq $MUTEX, %rdi
xorl $LLL_SHARED, %esi
callq __lll_lock_wait
subq $MUTEX, %rdi
jmp 2b
4: movl PRIVATE(%rdi), %esi
addq $MUTEX, %rdi
xorl $LLL_SHARED, %esi
callq __lll_unlock_wake
jmp 5b
6: movl PRIVATE(%rdi), %esi
addq $MUTEX, %rdi
xorl $LLL_SHARED, %esi
callq __lll_unlock_wake
subq $MUTEX, %rdi
jmp 7b
9: movl PRIVATE(%rdi), %esi
addq $MUTEX, %rdi
xorl $LLL_SHARED, %esi
callq __lll_unlock_wake
jmp 10b
.size __pthread_barrier_wait,.-__pthread_barrier_wait
weak_alias (__pthread_barrier_wait, pthread_barrier_wait)