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18 Commits

Author SHA1 Message Date
Adhemerval Zanella
06be6368da nptl: Define __PTHREAD_MUTEX_{NUSERS_AFTER_KIND,USE_UNION} 
This patch adds two new internal defines to set the internal
pthread_mutex_t layout required by the supported ABIS:

  1. __PTHREAD_MUTEX_NUSERS_AFTER_KIND which control whether to define
     __nusers fields before or after __kind.  The preferred value for
     is 0 for new ports and it sets __nusers before __kind.

  2. __PTHREAD_MUTEX_USE_UNION which control whether internal __spins and
     __list members will be place inside an union for linuxthreads
     compatibility.  The preferred value is 0 for ports and it sets
     to not use an union to define both fields.

It fixes the wrong offsets value for __kind value on x86_64-linux-gnu-x32.
Checked with a make check run-built-tests=no on all afected ABIs.

	[BZ #22298]
	* nptl/allocatestack.c (allocate_stack): Check if
	__PTHREAD_MUTEX_HAVE_PREV is non-zero, instead if
	__PTHREAD_MUTEX_HAVE_PREV is defined.
	* nptl/descr.h (pthread): Likewise.
	* nptl/nptl-init.c (__pthread_initialize_minimal_internal):
	Likewise.
	* nptl/pthread_create.c (START_THREAD_DEFN): Likewise.
	* sysdeps/nptl/fork.c (__libc_fork): Likewise.
	* sysdeps/nptl/pthread.h (PTHREAD_MUTEX_INITIALIZER): Likewise.
	* sysdeps/nptl/bits/thread-shared-types.h
	(__PTHREAD_MUTEX_NUSERS_AFTER_KIND, __PTHREAD_MUTEX_USE_UNION): New
	defines.
	(__pthread_internal_list): Check __PTHREAD_MUTEX_USE_UNION instead
	of __WORDSIZE for internal layout.
	(__pthread_mutex_s): Check __PTHREAD_MUTEX_NUSERS_AFTER_KIND instead
	of __WORDSIZE for internal __nusers layout and __PTHREAD_MUTEX_USE_UNION
	instead of __WORDSIZE whether to use an union for __spins and __list
	fields.
	(__PTHREAD_MUTEX_HAVE_PREV): Define also for __PTHREAD_MUTEX_USE_UNION
	case.
	* sysdeps/aarch64/nptl/bits/pthreadtypes-arch.h
	(__PTHREAD_MUTEX_NUSERS_AFTER_KIND, __PTHREAD_MUTEX_USE_UNION): New
	defines.
	* sysdeps/alpha/nptl/bits/pthreadtypes-arch.h
	(__PTHREAD_MUTEX_NUSERS_AFTER_KIND, __PTHREAD_MUTEX_USE_UNION):
	Likewise.
	* sysdeps/arm/nptl/bits/pthreadtypes-arch.h
	(__PTHREAD_MUTEX_NUSERS_AFTER_KIND, __PTHREAD_MUTEX_USE_UNION):
	Likewise.
	* sysdeps/hppa/nptl/bits/pthreadtypes-arch.h
	(__PTHREAD_MUTEX_NUSERS_AFTER_KIND, __PTHREAD_MUTEX_USE_UNION):
	Likewise.
	* sysdeps/ia64/nptl/bits/pthreadtypes-arch.h
	(__PTHREAD_MUTEX_NUSERS_AFTER_KIND, __PTHREAD_MUTEX_USE_UNION):
	Likewise.
	* sysdeps/m68k/nptl/bits/pthreadtypes-arch.h
	(__PTHREAD_MUTEX_NUSERS_AFTER_KIND, __PTHREAD_MUTEX_USE_UNION):
	Likewise.
	* sysdeps/microblaze/nptl/bits/pthreadtypes-arch.h
	(__PTHREAD_MUTEX_NUSERS_AFTER_KIND, __PTHREAD_MUTEX_USE_UNION):
	Likewise.
	* sysdeps/mips/nptl/bits/pthreadtypes-arch.h
	(__PTHREAD_MUTEX_NUSERS_AFTER_KIND, __PTHREAD_MUTEX_USE_UNION):
	Likewise.
	* sysdeps/nios2/nptl/bits/pthreadtypes-arch.h
	(__PTHREAD_MUTEX_NUSERS_AFTER_KIND, __PTHREAD_MUTEX_USE_UNION):
	Likewise.
	* sysdeps/powerpc/nptl/bits/pthreadtypes-arch.h
	(__PTHREAD_MUTEX_NUSERS_AFTER_KIND, __PTHREAD_MUTEX_USE_UNION):
	Likewise.
	* sysdeps/s390/nptl/bits/pthreadtypes-arch.h
	(__PTHREAD_MUTEX_NUSERS_AFTER_KIND, __PTHREAD_MUTEX_USE_UNION):
	Likewise.
	* sysdeps/sh/nptl/bits/pthreadtypes-arch.h
	(__PTHREAD_MUTEX_NUSERS_AFTER_KIND, __PTHREAD_MUTEX_USE_UNION):
	Likewise.
	* sysdeps/sparc/nptl/bits/pthreadtypes-arch.h
	(__PTHREAD_MUTEX_NUSERS_AFTER_KIND, __PTHREAD_MUTEX_USE_UNION):
	Likewise.
	* sysdeps/tile/nptl/bits/pthreadtypes-arch.h
	(__PTHREAD_MUTEX_NUSERS_AFTER_KIND, __PTHREAD_MUTEX_USE_UNION):
	Likewise.
	* sysdeps/x86/nptl/bits/pthreadtypes-arch.h
	(__PTHREAD_MUTEX_NUSERS_AFTER_KIND, __PTHREAD_MUTEX_USE_UNION):
	Likewise.

Signed-off-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
 2017-11-07 09:48:41 -02:00
Adhemerval Zanella
dff91cd45e nptl: Add tests for internal pthread_mutex_t offsets 
This patch adds a new build test to check for internal fields
offsets for user visible internal field.  Although currently
the only field which is statically initialized to a non zero value
is pthread_mutex_t.__data.__kind value, the tests also check the
offset of __kind, __spins, __elision (if supported), and __list
internal member.  A internal header (pthread-offset.h) is added
to each major ABI with the reference value.

Checked on x86_64-linux-gnu and with a build check for all affected
ABIs (aarch64-linux-gnu, alpha-linux-gnu, arm-linux-gnueabihf,
hppa-linux-gnu, i686-linux-gnu, ia64-linux-gnu, m68k-linux-gnu,
microblaze-linux-gnu, mips64-linux-gnu, mips64-n32-linux-gnu,
mips-linux-gnu, powerpc64le-linux-gnu, powerpc-linux-gnu,
s390-linux-gnu, s390x-linux-gnu, sh4-linux-gnu, sparc64-linux-gnu,
sparcv9-linux-gnu, tilegx-linux-gnu, tilegx-linux-gnu-x32,
tilepro-linux-gnu, x86_64-linux-gnu, and x86_64-linux-x32).

	* nptl/pthreadP.h (ASSERT_PTHREAD_STRING,
	ASSERT_PTHREAD_INTERNAL_OFFSET): New macro.
	* nptl/pthread_mutex_init.c (__pthread_mutex_init): Add build time
	checks for internal pthread_mutex_t offsets.
	* sysdeps/aarch64/nptl/pthread-offsets.h
	(__PTHREAD_MUTEX_NUSERS_OFFSET, __PTHREAD_MUTEX_KIND_OFFSET,
	__PTHREAD_MUTEX_SPINS_OFFSET, __PTHREAD_MUTEX_ELISION_OFFSET,
	__PTHREAD_MUTEX_LIST_OFFSET): New macro.
	* sysdeps/alpha/nptl/pthread-offsets.h: Likewise.
	* sysdeps/arm/nptl/pthread-offsets.h: Likewise.
	* sysdeps/hppa/nptl/pthread-offsets.h: Likewise.
	* sysdeps/i386/nptl/pthread-offsets.h: Likewise.
	* sysdeps/ia64/nptl/pthread-offsets.h: Likewise.
	* sysdeps/m68k/nptl/pthread-offsets.h: Likewise.
	* sysdeps/microblaze/nptl/pthread-offsets.h: Likewise.
	* sysdeps/mips/nptl/pthread-offsets.h: Likewise.
	* sysdeps/nios2/nptl/pthread-offsets.h: Likewise.
	* sysdeps/powerpc/nptl/pthread-offsets.h: Likewise.
	* sysdeps/s390/nptl/pthread-offsets.h: Likewise.
	* sysdeps/sh/nptl/pthread-offsets.h: Likewise.
	* sysdeps/sparc/nptl/pthread-offsets.h: Likewise.
	* sysdeps/tile/nptl/pthread-offsets.h: Likewise.
	* sysdeps/x86_64/nptl/pthread-offsets.h: Likewise.

Signed-off-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
 2017-11-07 09:48:28 -02:00
Stefan Liebler
12d2dd7060 Optimize generic spinlock code and use C11 like atomic macros. 
This patch optimizes the generic spinlock code.

The type pthread_spinlock_t is a typedef to volatile int on all archs.
Passing a volatile pointer to the atomic macros which are not mapped to the
C11 atomic builtins can lead to extra stores and loads to stack if such
a macro creates a temporary variable by using "__typeof (*(mem)) tmp;".
Thus, those macros which are used by spinlock code - atomic_exchange_acquire,
atomic_load_relaxed, atomic_compare_exchange_weak - have to be adjusted.
According to the comment from  Szabolcs Nagy, the type of a cast expression is
unqualified (see http://www.open-std.org/jtc1/sc22/wg14/www/docs/dr_423.htm):
__typeof ((__typeof (*(mem)) *(mem)) tmp;
Thus from spinlock perspective the variable tmp is of type int instead of
type volatile int.  This patch adjusts those macros in include/atomic.h.
With this construct GCC >= 5 omits the extra stores and loads.

The atomic macros are replaced by the C11 like atomic macros and thus
the code is aligned to it.  The pthread_spin_unlock implementation is now
using release memory order instead of sequentially consistent memory order.
The issue with passed volatile int pointers applies to the C11 like atomic
macros as well as the ones used before.

I've added a glibc_likely hint to the first atomic exchange in
pthread_spin_lock in order to return immediately to the caller if the lock is
free.  Without the hint, there is an additional jump if the lock is free.

I've added the atomic_spin_nop macro within the loop of plain reads.
The plain reads are also realized by C11 like atomic_load_relaxed macro.

The new define ATOMIC_EXCHANGE_USES_CAS determines if the first try to acquire
the spinlock in pthread_spin_lock or pthread_spin_trylock is an exchange
or a CAS.  This is defined in atomic-machine.h for all architectures.

The define SPIN_LOCK_READS_BETWEEN_CMPXCHG is now removed.
There is no technical reason for throwing in a CAS every now and then,
and so far we have no evidence that it can improve performance.
If that would be the case, we have to adjust other spin-waiting loops
elsewhere, too!  Using a CAS loop without plain reads is not a good idea
on many targets and wasn't used by one.  Thus there is now no option to
do so.

Architectures are now using the generic spinlock automatically if they
do not provide an own implementation.  Thus the pthread_spin_lock.c files
in sysdeps folder are deleted.

ChangeLog:

	* NEWS: Mention new spinlock implementation.
	* include/atomic.h:
	(__atomic_val_bysize): Cast type to omit volatile qualifier.
	(atomic_exchange_acq): Likewise.
	(atomic_load_relaxed): Likewise.
	(ATOMIC_EXCHANGE_USES_CAS): Check definition.
	* nptl/pthread_spin_init.c (pthread_spin_init):
	Use atomic_store_relaxed.
	* nptl/pthread_spin_lock.c (pthread_spin_lock):
	Use C11-like atomic macros.
	* nptl/pthread_spin_trylock.c (pthread_spin_trylock):
	Likewise.
	* nptl/pthread_spin_unlock.c (pthread_spin_unlock):
	Use atomic_store_release.
	* sysdeps/aarch64/nptl/pthread_spin_lock.c: Delete File.
	* sysdeps/arm/nptl/pthread_spin_lock.c: Likewise.
	* sysdeps/hppa/nptl/pthread_spin_lock.c: Likewise.
	* sysdeps/m68k/nptl/pthread_spin_lock.c: Likewise.
	* sysdeps/microblaze/nptl/pthread_spin_lock.c: Likewise.
	* sysdeps/mips/nptl/pthread_spin_lock.c: Likewise.
	* sysdeps/nios2/nptl/pthread_spin_lock.c: Likewise.
	* sysdeps/aarch64/atomic-machine.h (ATOMIC_EXCHANGE_USES_CAS): Define.
	* sysdeps/alpha/atomic-machine.h: Likewise.
	* sysdeps/arm/atomic-machine.h: Likewise.
	* sysdeps/i386/atomic-machine.h: Likewise.
	* sysdeps/ia64/atomic-machine.h: Likewise.
	* sysdeps/m68k/coldfire/atomic-machine.h: Likewise.
	* sysdeps/m68k/m680x0/m68020/atomic-machine.h: Likewise.
	* sysdeps/microblaze/atomic-machine.h: Likewise.
	* sysdeps/mips/atomic-machine.h: Likewise.
	* sysdeps/powerpc/powerpc32/atomic-machine.h: Likewise.
	* sysdeps/powerpc/powerpc64/atomic-machine.h: Likewise.
	* sysdeps/s390/atomic-machine.h: Likewise.
	* sysdeps/sparc/sparc32/atomic-machine.h: Likewise.
	* sysdeps/sparc/sparc32/sparcv9/atomic-machine.h: Likewise.
	* sysdeps/sparc/sparc64/atomic-machine.h: Likewise.
	* sysdeps/tile/tilegx/atomic-machine.h: Likewise.
	* sysdeps/tile/tilepro/atomic-machine.h: Likewise.
	* sysdeps/unix/sysv/linux/hppa/atomic-machine.h: Likewise.
	* sysdeps/unix/sysv/linux/m68k/coldfire/atomic-machine.h: Likewise.
	* sysdeps/unix/sysv/linux/nios2/atomic-machine.h: Likewise.
	* sysdeps/unix/sysv/linux/sh/atomic-machine.h: Likewise.
	* sysdeps/x86_64/atomic-machine.h: Likewise.
 2017-06-06 09:41:56 +02:00
Adhemerval Zanella
eab380d8ec Move shared pthread definitions to common headers 
This patch removes all the replicated pthread definition accross the
architectures and consolidates it on shared headers.  The new
organization is as follow:

  * Architecture specific definition (such as pthread types sizes) are
    place in the new pthreadtypes-arch.h header in arch specific path.

  * All shared structure definition are moved to a common NPTL header
    at sysdeps/nptl/bits/pthreadtypes.h (with now includes the arch
    specific one for internal definitions).

  * Also, for C11 future thread support, both mutex and condition
    definition are placed in a common header at
    sysdeps/nptl/bits/thread-shared-types.h.

It is also a refactor patch without expected functional changes.
Checked with a build for all major ABI (aarch64-linux-gnu, alpha-linux-gnu,
arm-linux-gnueabi, i386-linux-gnu, ia64-linux-gnu,
m68k-linux-gnu, microblaze-linux-gnu, mips{64}-linux-gnu, nios2-linux-gnu,
powerpc{64le}-linux-gnu, s390{x}-linux-gnu, sparc{64}-linux-gnu,
tile{pro,gx}-linux-gnu, and x86_64-linux-gnu).

	* posix/Makefile (headers): Add pthreadtypes-arch.h and
	thread-shared-types.h.
	* sysdeps/aarch64/nptl/bits/pthreadtypes-arch.h: New file: arch
	specific thread definition.
	* sysdeps/alpha/nptl/bits/pthreadtypes-arch.h: Likewise.
	* sysdeps/arm/nptl/bits/pthreadtypes-arch.h: Likewise.
	* sysdeps/hppa/nptl/bits/pthreadtypes-arch.h: Likewise.
	* sysdeps/ia64/nptl/bits/pthreadtypes-arch.h: Likewise.
	* sysdeps/m68k/nptl/bits/pthreadtypes-arch.h: Likewise.
	* sysdeps/microblaze/nptl/bits/pthreadtypes-arch.h: Likewise.
	* sysdeps/mips/nptl/bits/pthreadtypes-arch.h: Likewise.
	* sysdeps/nios2/nptl/bits/pthreadtypes-arch.h: Likewise.
	* sysdeps/powerpc/nptl/bits/pthreadtypes-arch.h: Likewise.
	* sysdeps/s390/nptl/bits/pthreadtypes-arch.h: Likewise.
	* sysdeps/sh/nptl/bits/pthreadtypes-arch.h: Likewise.
	* sysdeps/sparc/nptl/bits/pthreadtypes-arch.h: Likewise.
	* sysdeps/tile/nptl/bits/pthreadtypes-arch.h: Likewise.
	* sysdeps/x86/nptl/bits/pthreadtypes-arch.h: Likewise.
	* sysdeps/nptl/bits/thread-shared-types.h: New file: shared
	thread definition between POSIX and C11.
	* sysdeps/aarch64/nptl/bits/pthreadtypes.h.: Remove file.
	* sysdeps/alpha/nptl/bits/pthreadtypes.h: Likewise.
	* sysdeps/arm/nptl/bits/pthreadtypes.h: Likewise.
	* sysdeps/hppa/nptl/bits/pthreadtypes.h: Likewise.
	* sysdeps/m68k/nptl/bits/pthreadtypes.h: Likewise.
	* sysdeps/microblaze/nptl/bits/pthreadtypes.h: Likewise.
	* sysdeps/mips/nptl/bits/pthreadtypes.h: Likewise.
	* sysdeps/nios2/nptl/bits/pthreadtypes.h: Likewise.
	* sysdeps/ia64/nptl/bits/pthreadtypes.h: Likewise.
	* sysdeps/powerpc/nptl/bits/pthreadtypes.h: Likewise.
	* sysdeps/s390/nptl/bits/pthreadtypes.h: Likewise.
	* sysdeps/sh/nptl/bits/pthreadtypes.h: Likewise.
	* sysdeps/sparc/nptl/bits/pthreadtypes.h: Likewise.
	* sysdeps/tile/nptl/bits/pthreadtypes.h: Likewise.
	* sysdeps/x86/nptl/bits/pthreadtypes.h: Likewise.
	* sysdeps/nptl/bits/pthreadtypes.h: New file: common thread
	definitions shared across all architectures.
 2017-05-09 17:49:17 -03:00
Torvald Riegel
cc25c8b4c1 New pthread rwlock that is more scalable. 
This replaces the pthread rwlock with a new implementation that uses a
more scalable algorithm (primarily through not using a critical section
anymore to make state changes).  The fast path for rdlock acquisition and
release is now basically a single atomic read-modify write or CAS and a few
branches.  See nptl/pthread_rwlock_common.c for details.

	* nptl/DESIGN-rwlock.txt: Remove.
	* nptl/lowlevelrwlock.sym: Remove.
	* nptl/Makefile: Add new tests.
	* nptl/pthread_rwlock_common.c: New file.  Contains the new rwlock.
	* nptl/pthreadP.h (PTHREAD_RWLOCK_PREFER_READER_P): Remove.
	(PTHREAD_RWLOCK_WRPHASE, PTHREAD_RWLOCK_WRLOCKED,
	PTHREAD_RWLOCK_RWAITING, PTHREAD_RWLOCK_READER_SHIFT,
	PTHREAD_RWLOCK_READER_OVERFLOW, PTHREAD_RWLOCK_WRHANDOVER,
	PTHREAD_RWLOCK_FUTEX_USED): New.
	* nptl/pthread_rwlock_init.c (__pthread_rwlock_init): Adapt to new
	implementation.
	* nptl/pthread_rwlock_rdlock.c (__pthread_rwlock_rdlock_slow): Remove.
	(__pthread_rwlock_rdlock): Adapt.
	* nptl/pthread_rwlock_timedrdlock.c
	(pthread_rwlock_timedrdlock): Adapt.
	* nptl/pthread_rwlock_timedwrlock.c
	(pthread_rwlock_timedwrlock): Adapt.
	* nptl/pthread_rwlock_trywrlock.c (pthread_rwlock_trywrlock): Adapt.
	* nptl/pthread_rwlock_tryrdlock.c (pthread_rwlock_tryrdlock): Adapt.
	* nptl/pthread_rwlock_unlock.c (pthread_rwlock_unlock): Adapt.
	* nptl/pthread_rwlock_wrlock.c (__pthread_rwlock_wrlock_slow): Remove.
	(__pthread_rwlock_wrlock): Adapt.
	* nptl/tst-rwlock10.c: Adapt.
	* nptl/tst-rwlock11.c: Adapt.
	* nptl/tst-rwlock17.c: New file.
	* nptl/tst-rwlock18.c: New file.
	* nptl/tst-rwlock19.c: New file.
	* nptl/tst-rwlock2b.c: New file.
	* nptl/tst-rwlock8.c: Adapt.
	* nptl/tst-rwlock9.c: Adapt.
	* sysdeps/aarch64/nptl/bits/pthreadtypes.h (pthread_rwlock_t): Adapt.
	* sysdeps/arm/nptl/bits/pthreadtypes.h (pthread_rwlock_t): Adapt.
	* sysdeps/hppa/nptl/bits/pthreadtypes.h (pthread_rwlock_t): Adapt.
	* sysdeps/ia64/nptl/bits/pthreadtypes.h (pthread_rwlock_t): Adapt.
	* sysdeps/m68k/nptl/bits/pthreadtypes.h (pthread_rwlock_t): Adapt.
	* sysdeps/microblaze/nptl/bits/pthreadtypes.h (pthread_rwlock_t): Adapt.
	* sysdeps/mips/nptl/bits/pthreadtypes.h (pthread_rwlock_t): Adapt.
	* sysdeps/nios2/nptl/bits/pthreadtypes.h (pthread_rwlock_t): Adapt.
	* sysdeps/s390/nptl/bits/pthreadtypes.h (pthread_rwlock_t): Adapt.
	* sysdeps/sh/nptl/bits/pthreadtypes.h (pthread_rwlock_t): Adapt.
	* sysdeps/sparc/nptl/bits/pthreadtypes.h (pthread_rwlock_t): Adapt.
	* sysdeps/tile/nptl/bits/pthreadtypes.h (pthread_rwlock_t): Adapt.
	* sysdeps/unix/sysv/linux/alpha/bits/pthreadtypes.h
	(pthread_rwlock_t): Adapt.
	* sysdeps/unix/sysv/linux/powerpc/bits/pthreadtypes.h
	(pthread_rwlock_t): Adapt.
	* sysdeps/x86/bits/pthreadtypes.h (pthread_rwlock_t): Adapt.
	* nptl/nptl-printers.py (): Adapt.
	* nptl/nptl_lock_constants.pysym: Adapt.
	* nptl/test-rwlock-printers.py: Adapt.
	* nptl/test-rwlockattr-printers.c: Adapt.
	* nptl/test-rwlockattr-printers.py: Adapt.
 2017-01-10 11:50:17 +01:00
Joseph Myers
bfff8b1bec Update copyright dates with scripts/update-copyrights. 2017-01-01 00:14:16 +00:00
Torvald Riegel
ed19993b5b New condvar implementation that provides stronger ordering guarantees. 
This is a new implementation for condition variables, required
after http://austingroupbugs.net/view.php?id=609 to fix bug 13165.  In
essence, we need to be stricter in which waiters a signal or broadcast
is required to wake up; this couldn't be solved using the old algorithm.
ISO C++ made a similar clarification, so this also fixes a bug in
current libstdc++, for example.

We can't use the old algorithm anymore because futexes do not guarantee
to wake in FIFO order.  Thus, when we wake, we can't simply let any
waiter grab a signal, but we need to ensure that one of the waiters
happening before the signal is woken up.  This is something the previous
algorithm violated (see bug 13165).

There's another issue specific to condvars: ABA issues on the underlying
futexes.  Unlike mutexes that have just three states, or semaphores that
have no tokens or a limited number of them, the state of a condvar is
the *order* of the waiters.  A waiter on a semaphore can grab a token
whenever one is available; a condvar waiter must only consume a signal
if it is eligible to do so as determined by the relative order of the
waiter and the signal.
Therefore, this new algorithm maintains two groups of waiters: Those
eligible to consume signals (G1), and those that have to wait until
previous waiters have consumed signals (G2).  Once G1 is empty, G2
becomes the new G1.  64b counters are used to avoid ABA issues.

This condvar doesn't yet use a requeue optimization (ie, on a broadcast,
waking just one thread and requeueing all others on the futex of the
mutex supplied by the program).  I don't think doing the requeue is
necessarily the right approach (but I haven't done real measurements
yet):
* If a program expects to wake many threads at the same time and make
that scalable, a condvar isn't great anyway because of how it requires
waiters to operate mutually exclusive (due to the mutex usage).  Thus, a
thundering herd problem is a scalability problem with or without the
optimization.  Using something like a semaphore might be more
appropriate in such a case.
* The scalability problem is actually at the mutex side; the condvar
could help (and it tries to with the requeue optimization), but it
should be the mutex who decides how that is done, and whether it is done
at all.
* Forcing all but one waiter into the kernel-side wait queue of the
mutex prevents/avoids the use of lock elision on the mutex.  Thus, it
prevents the only cure against the underlying scalability problem
inherent to condvars.
* If condvars use short critical sections (ie, hold the mutex just to
check a binary flag or such), which they should do ideally, then forcing
all those waiter to proceed serially with kernel-based hand-off (ie,
futex ops in the mutex' contended state, via the futex wait queues) will
be less efficient than just letting a scalable mutex implementation take
care of it.  Our current mutex impl doesn't employ spinning at all, but
if critical sections are short, spinning can be much better.
* Doing the requeue stuff requires all waiters to always drive the mutex
into the contended state.  This leads to each waiter having to call
futex_wake after lock release, even if this wouldn't be necessary.

	[BZ #13165]
	* nptl/pthread_cond_broadcast.c (__pthread_cond_broadcast): Rewrite to
	use new algorithm.
	* nptl/pthread_cond_destroy.c (__pthread_cond_destroy): Likewise.
	* nptl/pthread_cond_init.c (__pthread_cond_init): Likewise.
	* nptl/pthread_cond_signal.c (__pthread_cond_signal): Likewise.
	* nptl/pthread_cond_wait.c (__pthread_cond_wait): Likewise.
	(__pthread_cond_timedwait): Move here from pthread_cond_timedwait.c.
	(__condvar_confirm_wakeup, __condvar_cancel_waiting,
	__condvar_cleanup_waiting, __condvar_dec_grefs,
	__pthread_cond_wait_common): New.
	(__condvar_cleanup): Remove.
	* npt/pthread_condattr_getclock.c (pthread_condattr_getclock): Adapt.
	* npt/pthread_condattr_setclock.c (pthread_condattr_setclock):
	Likewise.
	* npt/pthread_condattr_getpshared.c (pthread_condattr_getpshared):
	Likewise.
	* npt/pthread_condattr_init.c (pthread_condattr_init): Likewise.
	* nptl/tst-cond1.c: Add comment.
	* nptl/tst-cond20.c (do_test): Adapt.
	* nptl/tst-cond22.c (do_test): Likewise.
	* sysdeps/aarch64/nptl/bits/pthreadtypes.h (pthread_cond_t): Adapt
	structure.
	* sysdeps/arm/nptl/bits/pthreadtypes.h (pthread_cond_t): Likewise.
	* sysdeps/ia64/nptl/bits/pthreadtypes.h (pthread_cond_t): Likewise.
	* sysdeps/m68k/nptl/bits/pthreadtypes.h (pthread_cond_t): Likewise.
	* sysdeps/microblaze/nptl/bits/pthreadtypes.h (pthread_cond_t):
	Likewise.
	* sysdeps/mips/nptl/bits/pthreadtypes.h (pthread_cond_t): Likewise.
	* sysdeps/nios2/nptl/bits/pthreadtypes.h (pthread_cond_t): Likewise.
	* sysdeps/s390/nptl/bits/pthreadtypes.h (pthread_cond_t): Likewise.
	* sysdeps/sh/nptl/bits/pthreadtypes.h (pthread_cond_t): Likewise.
	* sysdeps/tile/nptl/bits/pthreadtypes.h (pthread_cond_t): Likewise.
	* sysdeps/unix/sysv/linux/alpha/bits/pthreadtypes.h (pthread_cond_t):
	Likewise.
	* sysdeps/unix/sysv/linux/powerpc/bits/pthreadtypes.h (pthread_cond_t):
	Likewise.
	* sysdeps/x86/bits/pthreadtypes.h (pthread_cond_t): Likewise.
	* sysdeps/nptl/internaltypes.h (COND_NWAITERS_SHIFT): Remove.
	(COND_CLOCK_BITS): Adapt.
	* sysdeps/nptl/pthread.h (PTHREAD_COND_INITIALIZER): Adapt.
	* nptl/pthreadP.h (__PTHREAD_COND_CLOCK_MONOTONIC_MASK,
	__PTHREAD_COND_SHARED_MASK): New.
	* nptl/nptl-printers.py (CLOCK_IDS): Remove.
	(ConditionVariablePrinter, ConditionVariableAttributesPrinter): Adapt.
	* nptl/nptl_lock_constants.pysym: Adapt.
	* nptl/test-cond-printers.py: Adapt.
	* sysdeps/unix/sysv/linux/hppa/internaltypes.h (cond_compat_clear,
	cond_compat_check_and_clear): Adapt.
	* sysdeps/unix/sysv/linux/hppa/pthread_cond_timedwait.c: Remove file ...
	* sysdeps/unix/sysv/linux/hppa/pthread_cond_wait.c
	(__pthread_cond_timedwait): ... and move here.
	* nptl/DESIGN-condvar.txt: Remove file.
	* nptl/lowlevelcond.sym: Likewise.
	* nptl/pthread_cond_timedwait.c: Likewise.
	* sysdeps/unix/sysv/linux/i386/i486/pthread_cond_broadcast.S: Likewise.
	* sysdeps/unix/sysv/linux/i386/i486/pthread_cond_signal.S: Likewise.
	* sysdeps/unix/sysv/linux/i386/i486/pthread_cond_timedwait.S: Likewise.
	* sysdeps/unix/sysv/linux/i386/i486/pthread_cond_wait.S: Likewise.
	* sysdeps/unix/sysv/linux/i386/i586/pthread_cond_broadcast.S: Likewise.
	* sysdeps/unix/sysv/linux/i386/i586/pthread_cond_signal.S: Likewise.
	* sysdeps/unix/sysv/linux/i386/i586/pthread_cond_timedwait.S: Likewise.
	* sysdeps/unix/sysv/linux/i386/i586/pthread_cond_wait.S: Likewise.
	* sysdeps/unix/sysv/linux/i386/i686/pthread_cond_broadcast.S: Likewise.
	* sysdeps/unix/sysv/linux/i386/i686/pthread_cond_signal.S: Likewise.
	* sysdeps/unix/sysv/linux/i386/i686/pthread_cond_timedwait.S: Likewise.
	* sysdeps/unix/sysv/linux/i386/i686/pthread_cond_wait.S: Likewise.
	* sysdeps/unix/sysv/linux/x86_64/pthread_cond_broadcast.S: Likewise.
	* sysdeps/unix/sysv/linux/x86_64/pthread_cond_signal.S: Likewise.
	* sysdeps/unix/sysv/linux/x86_64/pthread_cond_timedwait.S: Likewise.
	* sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S: Likewise.
 2016-12-31 14:56:47 +01:00
Adhemerval Zanella
c579f48edb Remove cached PID/TID in clone 
This patch remove the PID cache and usage in current GLIBC code.  Current
usage is mainly used a performance optimization to avoid the syscall,
however it adds some issues:

  - The exposed clone syscall will try to set pid/tid to make the new
    thread somewhat compatible with current GLIBC assumptions.  This cause
    a set of issue with new workloads and usecases (such as BZ#17214 and
    [1]) as well for new internal usage of clone to optimize other algorithms
    (such as clone plus CLONE_VM for posix_spawn, BZ#19957).

  - The caching complexity also added some bugs in the past [2] [3] and
    requires more effort of each port to handle such requirements (for
    both clone and vfork implementation).

  - Caching performance gain in mainly on getpid and some specific
    code paths.  The getpid performance leverage is questionable [4],
    either by the idea of getpid being a hotspot as for the getpid
    implementation itself (if it is indeed a justifiable hotspot a
    vDSO symbol could let to a much more simpler solution).

    Other usage is mainly for non usual code paths, such as pthread
    cancellation signal and handling.

For thread creation (on stack allocation) the code simplification in fact
adds some performance gain due the no need of transverse the stack cache
and invalidate each element pid.

Other thread usages will require a direct getpid syscall, such as
cancellation/setxid signal, thread cancellation, thread fail path (at
create_thread), and thread signal (pthread_kill and pthread_sigqueue).
However these are hardly usual hotspots and I think adding a syscall is
justifiable.

It also simplifies both the clone and vfork arch-specific implementation.
And by review each fork implementation there are some discrepancies that
this patch also solves:

  - microblaze clone/vfork does not set/reset the pid/tid field
  - hppa uses the default vfork implementation that fallback to fork.
    Since vfork is deprecated I do not think we should bother with it.

The patch also removes the TID caching in clone. My understanding for
such semantic is try provide some pthread usage after a user program
issue clone directly (as done by thread creation with CLONE_PARENT_SETTID
and pthread tid member).  However, as stated before in multiple discussions
threads, GLIBC provides clone syscalls without further supporting all this
semantics.

I ran a full make check on x86_64, x32, i686, armhf, aarch64, and powerpc64le.
For sparc32, sparc64, and mips I ran the basic fork and vfork tests from
posix/ folder (on a qemu system).  So it would require further testing
on alpha, hppa, ia64, m68k, nios2, s390, sh, and tile (I excluded microblaze
because it is already implementing the patch semantic regarding clone/vfork).

[1] https://codereview.chromium.org/800183004/
[2] https://sourceware.org/ml/libc-alpha/2006-07/msg00123.html
[3] https://sourceware.org/bugzilla/show_bug.cgi?id=15368
[4] http://yarchive.net/comp/linux/getpid_caching.html

	* sysdeps/nptl/fork.c (__libc_fork): Remove pid cache setting.
	* nptl/allocatestack.c (allocate_stack): Likewise.
	(__reclaim_stacks): Likewise.
	(setxid_signal_thread): Obtain pid through syscall.
	* nptl/nptl-init.c (sigcancel_handler): Likewise.
	(sighandle_setxid): Likewise.
	* nptl/pthread_cancel.c (pthread_cancel): Likewise.
	* sysdeps/unix/sysv/linux/pthread_kill.c (__pthread_kill): Likewise.
	* sysdeps/unix/sysv/linux/pthread_sigqueue.c (pthread_sigqueue):
	Likewise.
	* sysdeps/unix/sysv/linux/createthread.c (create_thread): Likewise.
	* sysdeps/unix/sysv/linux/getpid.c: Remove file.
	* nptl/descr.h (struct pthread): Change comment about pid value.
	* nptl/pthread_getattr_np.c (pthread_getattr_np): Remove thread
	pid assert.
	* sysdeps/unix/sysv/linux/pthread-pids.h (__pthread_initialize_pids):
	Do not set pid value.
	* nptl_db/td_ta_thr_iter.c (iterate_thread_list): Remove thread
	pid cache check.
	* nptl_db/td_thr_validate.c (td_thr_validate): Likewise.
	* sysdeps/aarch64/nptl/tcb-offsets.sym: Remove pid offset.
	* sysdeps/alpha/nptl/tcb-offsets.sym: Likewise.
	* sysdeps/arm/nptl/tcb-offsets.sym: Likewise.
	* sysdeps/hppa/nptl/tcb-offsets.sym: Likewise.
	* sysdeps/i386/nptl/tcb-offsets.sym: Likewise.
	* sysdeps/ia64/nptl/tcb-offsets.sym: Likewise.
	* sysdeps/m68k/nptl/tcb-offsets.sym: Likewise.
	* sysdeps/microblaze/nptl/tcb-offsets.sym: Likewise.
	* sysdeps/mips/nptl/tcb-offsets.sym: Likewise.
	* sysdeps/nios2/nptl/tcb-offsets.sym: Likewise.
	* sysdeps/powerpc/nptl/tcb-offsets.sym: Likewise.
	* sysdeps/s390/nptl/tcb-offsets.sym: Likewise.
	* sysdeps/sh/nptl/tcb-offsets.sym: Likewise.
	* sysdeps/sparc/nptl/tcb-offsets.sym: Likewise.
	* sysdeps/tile/nptl/tcb-offsets.sym: Likewise.
	* sysdeps/x86_64/nptl/tcb-offsets.sym: Likewise.
	* sysdeps/unix/sysv/linux/aarch64/clone.S: Remove pid and tid caching.
	* sysdeps/unix/sysv/linux/alpha/clone.S: Likewise.
	* sysdeps/unix/sysv/linux/arm/clone.S: Likewise.
	* sysdeps/unix/sysv/linux/hppa/clone.S: Likewise.
	* sysdeps/unix/sysv/linux/i386/clone.S: Likewise.
	* sysdeps/unix/sysv/linux/ia64/clone2.S: Likewise.
	* sysdeps/unix/sysv/linux/mips/clone.S: Likewise.
	* sysdeps/unix/sysv/linux/nios2/clone.S: Likewise.
	* sysdeps/unix/sysv/linux/powerpc/powerpc32/clone.S: Likewise.
	* sysdeps/unix/sysv/linux/powerpc/powerpc64/clone.S: Likewise.
	* sysdeps/unix/sysv/linux/s390/s390-32/clone.S: Likewise.
	* sysdeps/unix/sysv/linux/s390/s390-64/clone.S: Likewise.
	* sysdeps/unix/sysv/linux/sh/clone.S: Likewise.
	* sysdeps/unix/sysv/linux/sparc/sparc32/clone.S: Likewise.
	* sysdeps/unix/sysv/linux/sparc/sparc64/clone.S: Likewise.
	* sysdeps/unix/sysv/linux/tile/clone.S: Likewise.
	* sysdeps/unix/sysv/linux/x86_64/clone.S: Likewise.
	* sysdeps/unix/sysv/linux/aarch64/vfork.S: Remove pid set and reset.
	* sysdeps/unix/sysv/linux/alpha/vfork.S: Likewise.
	* sysdeps/unix/sysv/linux/arm/vfork.S: Likewise.
	* sysdeps/unix/sysv/linux/i386/vfork.S: Likewise.
	* sysdeps/unix/sysv/linux/ia64/vfork.S: Likewise.
	* sysdeps/unix/sysv/linux/m68k/clone.S: Likewise.
	* sysdeps/unix/sysv/linux/m68k/vfork.S: Likewise.
	* sysdeps/unix/sysv/linux/mips/vfork.S: Likewise.
	* sysdeps/unix/sysv/linux/nios2/vfork.S: Likewise.
	* sysdeps/unix/sysv/linux/powerpc/powerpc32/vfork.S: Likewise.
	* sysdeps/unix/sysv/linux/powerpc/powerpc64/vfork.S: Likewise.
	* sysdeps/unix/sysv/linux/s390/s390-32/vfork.S: Likewise.
	* sysdeps/unix/sysv/linux/s390/s390-64/vfork.S: Likewise.
	* sysdeps/unix/sysv/linux/sh/vfork.S: Likewise.
	* sysdeps/unix/sysv/linux/sparc/sparc32/vfork.S: Likewise.
	* sysdeps/unix/sysv/linux/sparc/sparc64/vfork.S: Likewise.
	* sysdeps/unix/sysv/linux/tile/vfork.S: Likewise.
	* sysdeps/unix/sysv/linux/x86_64/vfork.S: Likewise.
	* sysdeps/unix/sysv/linux/tst-clone2.c (f): Remove direct pthread
	struct access.
	(clone_test): Remove function.
	(do_test): Rewrite to take in consideration pid is not cached anymore.
 2016-11-24 19:38:51 -02:00
Florian Weimer
c74940f2a7 nptl: Document the reason why __kind in pthread_mutex_t is part of the ABI 2016-11-07 20:24:32 +01:00
Florian Weimer
aca1daef29 elf: Consolidate machine-agnostic DTV definitions in <dl-dtv.h> 
Identical definitions of dtv_t and TLS_DTV_UNALLOCATED were
repeated for all architectures using DTVs.
 2016-06-20 14:31:40 +02:00
Joseph Myers
f7a9f785e5 Update copyright dates with scripts/update-copyrights. 2016-01-04 16:05:18 +00:00
Joseph Myers
b168057aaa Update copyright dates with scripts/update-copyrights. 2015-01-02 16:29:47 +00:00
Roland McGrath
15bed4728f m68k: Consolidate nptl/ subdirectories under linux/... 2014-06-23 09:24:18 -07:00
Roland McGrath
d752f0ccd7 m68k: Define TLS_DEFINE_INIT_TP 2014-06-09 15:54:19 -07:00
Andreas Schwab
774f928582 Remove second argument from TLS_INIT_TP macro 2014-05-27 14:48:46 +02:00
Roland McGrath
e0db65176f Clean up __exit_thread. 2014-05-13 09:49:20 -07:00
Roland McGrath
498a22333b Compile with -Wundef. 2014-03-14 11:32:51 -07:00
Andreas Schwab
73588a7223 Move m68k from ports to libc 2014-02-10 20:22:40 +01:00