S/390: Port of lock elision to System/z

  Hi,

this is a port of the lock elision implementation of Intel to System/z.
This is the continuation of Dominik Vogts patch
(https://sourceware.org/ml/libc-alpha/2013-11/msg00546.html).
The lock elision code is only built with --enable-lock-elision=yes.
Then default mutexes are elided via __builtin_tbegin, if the cpu
supports transactions. By default lock elision is not enabled and the
elision code is not built (Intel always builds the elision code).
This is necessary in order to compile glibc on S/390 with an gcc
without transactions-support. The requirements on gcc are
checked by configure-script. Binutils are needed in version 2.24,
which is already checked by configure-script.
The patch is tested on S390 / S390x with lock-elision enabled /disabled.

This implementation breaks pthread_mutex_destroy in the same way as 
described in Bug 16657.

Ok?

Bye

---
2014-04-24  Stefan Liebler  <stli@linux.vnet.ibm.com>

	* config.make.in (enable-lock-elision): New Makefile variable.
	* configure.ac: Likewise.
	* configure: Regenerate.
	* sysdeps/s390/configure.ac:
	Add check for gcc transactions support.
	* sysdeps/s390/configure: Regenerate.
	* nptl/sysdeps/unix/sysv/linux/s390/Makefile: New file.
	Build elision files if enabled.
	* nptl/sysdeps/unix/sysv/linux/s390/elision-conf.c: New file.
	Add lock elision support for s390.
	* nptl/sysdeps/unix/sysv/linux/s390/elision-conf.h: Likewise.
	* nptl/sysdeps/unix/sysv/linux/s390/elision-lock.c: Likewise.
	* nptl/sysdeps/unix/sysv/linux/s390/elision-timed.c: Likewise.
	* nptl/sysdeps/unix/sysv/linux/s390/elision-trylock.c: Likewise.
	* nptl/sysdeps/unix/sysv/linux/s390/elision-unlock.c: Likewise.
	* nptl/sysdeps/unix/sysv/linux/s390/force-elision.h: Likewise.
	* nptl/sysdeps/unix/sysv/linux/s390/pthread_mutex_cond_lock.c:
	Likewise.
	* nptl/sysdeps/unix/sysv/linux/s390/pthread_mutex_lock.c:
	Likewise.
	* nptl/sysdeps/unix/sysv/linux/s390/pthread_mutex_timedlock.c:
	Likewise.
	* nptl/sysdeps/unix/sysv/linux/s390/pthread_mutex_trylock.c:
	Likewise.
	* nptl/sysdeps/unix/sysv/linux/s390/pthread_mutex_unlock.c:
	Likewise.
	* nptl/sysdeps/unix/sysv/linux/s390/lowlevellock.h:
	(__lll_timedlock_elision, __lll_lock_elision)
	(__lll_unlock_elision, __lll_trylock_elision)
	(lll_timedlock_elision, lll_lock_elision)
	(lll_unlock_elision, lll_trylock_elision): Add.
	* nptl/sysdeps/unix/sysv/linux/s390/bits/pthreadtypes.h
	(pthread_mutex_t): Add lock elision support for s390.
---
  

Stefan Liebler <stli@linux.vnet.ibm.com> writes:
>
> This implementation breaks pthread_mutex_destroy in the same way as
> described in Bug 16657.

Patch looks ok to me from a quick read.

-Andi
  

Hi Stefan

I think the patch adds to much code duplication based on x86 version, it calls for 
some refactoring.  Just comments below:


On 24-04-2014 11:42, Stefan Liebler wrote:
> Hi,
>
> this is a port of the lock elision implementation of Intel to System/z.
> This is the continuation of Dominik Vogts patch
> (https://sourceware.org/ml/libc-alpha/2013-11/msg00546.html).
> The lock elision code is only built with --enable-lock-elision=yes.
> Then default mutexes are elided via __builtin_tbegin, if the cpu
> supports transactions. By default lock elision is not enabled and the
> elision code is not built (Intel always builds the elision code).
> This is necessary in order to compile glibc on S/390 with an gcc
> without transactions-support. The requirements on gcc are
> checked by configure-script. Binutils are needed in version 2.24,
> which is already checked by configure-script.
> The patch is tested on S390 / S390x with lock-elision enabled /disabled.
>
> This implementation breaks pthread_mutex_destroy in the same way as described in Bug 16657.
>
> Ok?
>
> Bye
>
> ---
> 2014-04-24  Stefan Liebler  <stli@linux.vnet.ibm.com>
>
>     * config.make.in (enable-lock-elision): New Makefile variable.
>     * configure.ac: Likewise.
>     * configure: Regenerate.
>     * sysdeps/s390/configure.ac:
>     Add check for gcc transactions support.
>     * sysdeps/s390/configure: Regenerate.
>     * nptl/sysdeps/unix/sysv/linux/s390/Makefile: New file.
>     Build elision files if enabled.
>     * nptl/sysdeps/unix/sysv/linux/s390/elision-conf.c: New file.
>     Add lock elision support for s390.
>     * nptl/sysdeps/unix/sysv/linux/s390/elision-conf.h: Likewise.
>     * nptl/sysdeps/unix/sysv/linux/s390/elision-lock.c: Likewise.
>     * nptl/sysdeps/unix/sysv/linux/s390/elision-timed.c: Likewise.
>     * nptl/sysdeps/unix/sysv/linux/s390/elision-trylock.c: Likewise.
>     * nptl/sysdeps/unix/sysv/linux/s390/elision-unlock.c: Likewise.
>     * nptl/sysdeps/unix/sysv/linux/s390/force-elision.h: Likewise.
>     * nptl/sysdeps/unix/sysv/linux/s390/pthread_mutex_cond_lock.c:
>     Likewise.
>     * nptl/sysdeps/unix/sysv/linux/s390/pthread_mutex_lock.c:
>     Likewise.
>     * nptl/sysdeps/unix/sysv/linux/s390/pthread_mutex_timedlock.c:
>     Likewise.
>     * nptl/sysdeps/unix/sysv/linux/s390/pthread_mutex_trylock.c:
>     Likewise.
>     * nptl/sysdeps/unix/sysv/linux/s390/pthread_mutex_unlock.c:
>     Likewise.
>     * nptl/sysdeps/unix/sysv/linux/s390/lowlevellock.h:
>     (__lll_timedlock_elision, __lll_lock_elision)
>     (__lll_unlock_elision, __lll_trylock_elision)
>     (lll_timedlock_elision, lll_lock_elision)
>     (lll_unlock_elision, lll_trylock_elision): Add.
>     * nptl/sysdeps/unix/sysv/linux/s390/bits/pthreadtypes.h
>     (pthread_mutex_t): Add lock elision support for s390.
> ---
>
> diff --git a/nptl/sysdeps/unix/sysv/linux/s390/elision-conf.c b/nptl/sysdeps/unix/sysv/linux/s390/elision-conf.c
> new file mode 100644
> index 0000000..b92e0ea
> --- /dev/null
> +++ b/nptl/sysdeps/unix/sysv/linux/s390/elision-conf.c
> @@ -0,0 +1,81 @@
> +/* Lock elision tunable parameters.
> +   Copyright (C) 2014 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/>.  */
> +
> +#include <config.h>
> +#include <pthreadP.h>
> +#include <elision-conf.h>
> +#include <unistd.h>
> +#include <dl-procinfo.h>
> +
> +/* Reasonable initial tuning values, may be revised in the future.
> +   This is a conservative initial value.  */
> +
> +struct elision_config __elision_aconf =
> +  {
> +    /* How often to not attempt to use elision if a transaction aborted
> +       because the lock is already acquired.  Expressed in number of lock
> +       acquisition attempts.  */
> +    .skip_lock_busy = 3,
> +    /* How often to not attempt to use elision if a transaction aborted due
> +       to reasons other than other threads' memory accesses.  Expressed in
> +       number of lock acquisition attempts.  */
> +    .skip_lock_internal_abort = 3,
> +    /* How often to not attempt to use elision if a lock used up all retries
> +       without success.  Expressed in number of lock acquisition attempts.  */
> +    .skip_lock_out_of_tbegin_retries = 3,
> +    /* How often we try using elision if there is chance for the transaction
> +       to finish execution (e.g., it wasn't aborted due to the lock being
> +       already acquired.  */
> +    .try_tbegin = 3,
> +    /* Same as SKIP_LOCK_INTERNAL_ABORT but for trylock.  */
> +    .skip_trylock_internal_abort = 3,
> +  };
> +
> +/* Force elision for all new locks.  This is used to decide whether existing
> +   DEFAULT locks should be automatically upgraded to elision in
> +   pthread_mutex_lock().  Disabled for suid programs.  Only used when elision
> +   is available.  */
> +
> +int __pthread_force_elision attribute_hidden = 0;
> +
> +/* Initialize elison.  */
> +
> +static void
> +elision_init (int argc __attribute__ ((unused)),
> +	      char **argv  __attribute__ ((unused)),
> +	      char **environ)
> +{
> +  /* Set when the CPU supports elision. When false elision is never attempted.  */
> +  int elision_available = (GLRO (dl_hwcap) & HWCAP_S390_TE) ? 1 : 0;
> +
> +  __pthread_force_elision = __libc_enable_secure ? 0 : elision_available;
> +}
> +
> +#ifdef SHARED
> +# define INIT_SECTION ".init_array"
> +# define MAYBE_CONST
> +#else
> +# define INIT_SECTION ".preinit_array"
> +# define MAYBE_CONST const
> +#endif
> +
> +void (*MAYBE_CONST __pthread_init_array []) (int, char **, char **)
> +  __attribute__ ((section (INIT_SECTION), aligned (sizeof (void *)))) =
> +{
> +  &elision_init
> +};

Although correct, this code shared a lot of logic with x86 version.  I wonder if we could
use a common base to avoid code duplication.

> diff --git a/nptl/sysdeps/unix/sysv/linux/s390/elision-lock.c b/nptl/sysdeps/unix/sysv/linux/s390/elision-lock.c
> new file mode 100644
> index 0000000..89b647c
> --- /dev/null
> +++ b/nptl/sysdeps/unix/sysv/linux/s390/elision-lock.c
> @@ -0,0 +1,123 @@
> +/* Elided pthread mutex lock.
> +   Copyright (C) 2014 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/>.  */
> +
> +#include <pthread.h>
> +#include <pthreadP.h>
> +#include <lowlevellock.h>
> +#include <htmintrin.h>
> +#include <elision-conf.h>
> +#include <stdint.h>
> +
> +#if !defined(LLL_LOCK) && !defined(EXTRAARG)
> +/* Make sure the configuration code is always linked in for static
> +   libraries.  */
> +#include "elision-conf.c"
> +#endif
> +
> +#ifndef EXTRAARG
> +#define EXTRAARG
> +#endif
> +#ifndef LLL_LOCK
> +#define LLL_LOCK(a,b) lll_lock(a,b), 0
> +#endif
> +
> +#define aconf __elision_aconf
> +
> +/* Adaptive lock using transactions.
> +   By default the lock region is run as a transaction, and when it
> +   aborts or the lock is busy the lock adapts itself.  */
> +
> +int
> +__lll_lock_elision (int *futex, short *adapt_count, EXTRAARG int private)
> +{
> +  if (*adapt_count <= 0)
> +    {
> +      __asm__ volatile (".machinemode \"zarch_nohighgprs\"\n\t"
> +			".machine \"all\""
> +			: : : "memory");
> +
> +      int try_tbegin;
> +      for (try_tbegin = aconf.try_tbegin;
> +	   try_tbegin > 0;
> +	   try_tbegin--)
> +	{
> +	  unsigned status;
> +	  if (__builtin_expect
> +	      ((status = __builtin_tbegin((void *)0)) == _HTM_TBEGIN_STARTED, 1))
> +	    {
> +	      if (*futex == 0)
> +		return 0;
> +	      /* Lock was busy.  Fall back to normal locking.  */
> +	      if (__builtin_expect (__builtin_tx_nesting_depth (), 1))
> +		{
> +		  /* In a non-nested transaction there is no need to abort,
> +		     which is expensive.  */
> +		  __builtin_tend ();
> +		  if (aconf.skip_lock_busy > 0)
> +		    *adapt_count = aconf.skip_lock_busy;
> +		  goto use_lock;
> +		}
> +	      else /* nesting depth is > 1 */
> +		{
> +		  /* A nested transaction will abort eventually because it
> +		     cannot make any progress before *futex changes back to 0.
> +		     So we may as well abort immediately.
> +		     This persistently aborts the outer transaction to force
> +		     the outer mutex use the default lock instead of retrying
> +		     with transactions until the try_tbegin of the outer mutex
> +		     is zero.
> +		     The adapt_count of this inner mutex is not changed,
> +		     because using the default lock with the inner mutex
> +		     would abort the outer transaction.
> +		  */
> +		  __builtin_tabort (_HTM_FIRST_USER_ABORT_CODE + 1);
> +		}
> +	    }
> +	  else
> +	    {
> +	      asm volatile ("" ::: "f0", "f1", "f2", "f3", "f4", "f5", "f6",
> +			    "f7", "f8", "f9", "f10", "f11", "f12", "f13",
> +			    "f14", "f15", "cc", "memory");

Just curious: why do you need this asm assembly? Some arch specific memory barrier? 

> +
> +	      if (status != _HTM_TBEGIN_TRANSIENT)
> +		{
> +		  /* A persistent abort (cc 1 or 3) indicates that a retry is
> +		     probably futile.  Use the normal locking now and for the
> +		     next couple of calls.
> +		     Be careful to avoid writing to the lock.  */
> +		  if (aconf.skip_lock_internal_abort > 0)
> +		    *adapt_count = aconf.skip_lock_internal_abort;
> +		  goto use_lock;
> +		}
> +	    }
> +	}
> +      /* Same logic as above, but for for a number of tepmorary failures in a
> +	 row.  */
> +      if (aconf.skip_lock_out_of_tbegin_retries > 0 && aconf.try_tbegin > 0)
> +	*adapt_count = aconf.skip_lock_out_of_tbegin_retries;
> +    }
> +  else
> +    {
> +      /* Lost updates are possible, but harmless.  Due to races this might lead
> +	 to *adapt_count becoming less than zero.  */
> +      (*adapt_count)--;
> +    }
> +
> +  use_lock:
> +  return LLL_LOCK ((*futex), private);
> +}
> diff --git a/nptl/sysdeps/unix/sysv/linux/s390/elision-timed.c b/nptl/sysdeps/unix/sysv/linux/s390/elision-timed.c
> new file mode 100644
> index 0000000..a8d8b2a
> --- /dev/null
> +++ b/nptl/sysdeps/unix/sysv/linux/s390/elision-timed.c
> @@ -0,0 +1,26 @@
> +/* Lock elision timed lock.
> +   Copyright (C) 2014 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/>.  */
> +
> +#include <time.h>
> +#include <elision-conf.h>
> +#include <lowlevellock.h>
> +#define __lll_lock_elision __lll_timedlock_elision
> +#define EXTRAARG const struct timespec *t,
> +#undef LLL_LOCK
> +#define LLL_LOCK(a, b) lll_timedlock(a, t, b)
> +#include "elision-lock.c"
> diff --git a/nptl/sysdeps/unix/sysv/linux/s390/elision-trylock.c b/nptl/sysdeps/unix/sysv/linux/s390/elision-trylock.c
> new file mode 100644
> index 0000000..8ec8c71
> --- /dev/null
> +++ b/nptl/sysdeps/unix/sysv/linux/s390/elision-trylock.c
> @@ -0,0 +1,97 @@
> +/* Elided pthread mutex trylock.
> +   Copyright (C) 2014 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/>.  */
> +
> +#include <pthread.h>
> +#include <pthreadP.h>
> +#include <lowlevellock.h>
> +#include <htmintrin.h>
> +#include <elision-conf.h>
> +
> +#define aconf __elision_aconf
> +
> +/* Try to elide a futex trylock.  FUTEX is the futex variable.  ADAPT_COUNT is
> +   the adaptation counter in the mutex.  */
> +
> +int
> +__lll_trylock_elision (int *futex, short *adapt_count)
> +{
> +  __asm__ volatile (".machinemode \"zarch_nohighgprs\"\n\t"
> +		    ".machine \"all\""
> +		    : : : "memory");
> +
> +  /* Implement POSIX semantics by forbiding nesting elided trylocks.
> +     Sorry.  After the abort the code is re-executed
> +     non transactional and if the lock was already locked
> +     return an error.  */
> +  if (__builtin_tx_nesting_depth () > 0)
> +    {
> +      /* Note that this abort may terminate an outermost transaction that
> +	 was created outside glibc.
> +	 This persistently aborts the current transactions to force
> +	 them to use the default lock instead of retrying transactions
> +	 until their try_tbegin is zero.
> +      */
> +      __builtin_tabort (_HTM_FIRST_USER_ABORT_CODE + 1);
> +    }
> +
> +  /* Only try a transaction if it's worth it.  */
> +  if (*adapt_count <= 0)
> +    {
> +      unsigned status;
> +
> +      if (__builtin_expect
> +	  ((status = __builtin_tbegin ((void *)0)) == _HTM_TBEGIN_STARTED, 1))
> +	{
> +	  if (*futex == 0)
> +	    return 0;
> +	  /* Lock was busy.  Fall back to normal locking.  */
> +	  /* Since we are in a non-nested transaction there is no need to abort,
> +	     which is expensive.  */
> +	  __builtin_tend ();
> +	  /* Note: Changing the adapt_count here might abort a transaction on a
> +	     different cpu, but that could happen anyway when the futex is
> +	     acquired, so there's no need to check the nesting depth here.  */
> +	  if (aconf.skip_lock_busy > 0)
> +	    *adapt_count = aconf.skip_lock_busy;
> +	}
> +      else
> +	{
> +	  asm volatile ("" ::: "f0", "f1", "f2", "f3", "f4", "f5", "f6", "f7",
> +			"f8", "f9", "f10", "f11", "f12", "f13", "f14", "f15",
> +			"cc", "memory");
> +	  if (status != _HTM_TBEGIN_TRANSIENT)
> +	    {
> +	      /* A persistent abort (cc 1 or 3) indicates that a retry is
> +		 probably futile.  Use the normal locking now and for the
> +		 next couple of calls.
> +		 Be careful to avoid writing to the lock.  */
> +	      if (aconf.skip_trylock_internal_abort > 0)
> +		*adapt_count = aconf.skip_trylock_internal_abort;
> +	    }
> +	}
> +      /* Could do some retries here.  */
> +    }
> +  else
> +    {
> +      /* Lost updates are possible, but harmless.  Due to races this might lead
> +	 to *adapt_count becoming less than zero.  */
> +      (*adapt_count)--;
> +    }
> +
> +  return lll_trylock (*futex);
> +}
> diff --git a/nptl/sysdeps/unix/sysv/linux/s390/elision-unlock.c b/nptl/sysdeps/unix/sysv/linux/s390/elision-unlock.c
> new file mode 100644
> index 0000000..44d05cb
> --- /dev/null
> +++ b/nptl/sysdeps/unix/sysv/linux/s390/elision-unlock.c
> @@ -0,0 +1,38 @@
> +/* Commit an elided pthread lock.
> +   Copyright (C) 2014 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/>.  */
> +
> +#include <pthreadP.h>
> +#include <lowlevellock.h>
> +
> +int
> +__lll_unlock_elision(int *lock, int private)
> +{
> +  /* If the lock is free, we elided the lock earlier.  This does not
> +     necessarily mean that we are in a transaction, because the user code may
> +     have closed the transaction, but that is impossible to detect reliably.  */
> +  if (*lock == 0)
> +    {
> +      __asm__ volatile (".machinemode \"zarch_nohighgprs\"\n\t"
> +			".machine \"all\""
> +			: : : "memory");
> +      __builtin_tend();
> +    }
> +  else
> +    lll_unlock ((*lock), private);
> +  return 0;
> +}
> diff --git a/nptl/sysdeps/unix/sysv/linux/s390/force-elision.h b/nptl/sysdeps/unix/sysv/linux/s390/force-elision.h
> new file mode 100644
> index 0000000..8fd7684
> --- /dev/null
> +++ b/nptl/sysdeps/unix/sysv/linux/s390/force-elision.h
> @@ -0,0 +1,33 @@
> +/* Automatic enabling of elision for mutexes
> +   Copyright (C) 2014 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/>.  */
> +
> +#ifdef ENABLE_LOCK_ELISION
> +/* Check for elision on this lock without upgrading.  */
> +#define DO_ELISION(m)							\
> +  (__pthread_force_elision						\
> +   && (m->__data.__kind & PTHREAD_MUTEX_NO_ELISION_NP) == 0)		\
> +
> +/* Automatically enable elision for existing user lock kinds.  */
> +#define FORCE_ELISION(m, s)						\
> +  if (__pthread_force_elision						\
> +      && (m->__data.__kind & PTHREAD_MUTEX_ELISION_FLAGS_NP) == 0)	\
> +    {									\
> +      mutex->__data.__kind |= PTHREAD_MUTEX_ELISION_NP;			\
> +      s;								\
> +    }
> +#endif

Again a lot of duplicated code from x86.  I don't think it is a good move to maintainability.

> diff --git a/nptl/sysdeps/unix/sysv/linux/s390/lowlevellock.h b/nptl/sysdeps/unix/sysv/linux/s390/lowlevellock.h
> index 864dcbc..3b6bc6e 100644
> --- a/nptl/sysdeps/unix/sysv/linux/s390/lowlevellock.h
> +++ b/nptl/sysdeps/unix/sysv/linux/s390/lowlevellock.h
> @@ -285,6 +285,15 @@ __lll_timedlock (int *futex, const struct timespec *abstime, int private)
>  #define lll_timedlock(futex, abstime, private) \
>    __lll_timedlock (&(futex), abstime, private)
>
> +#ifdef ENABLE_LOCK_ELISION
> +extern int __lll_timedlock_elision
> +  (int *futex, short *adapt_count, const struct timespec *timeout, int private)
> +  attribute_hidden;
> +
> +# define lll_timedlock_elision(futex, adapt_count, timeout, private)	\
> +  __lll_timedlock_elision(&(futex), &(adapt_count), timeout, private)
> +#endif
> +
>  static inline int
>  __attribute__ ((always_inline))
>  __lll_robust_timedlock (int *futex, const struct timespec *abstime,
> @@ -360,4 +369,22 @@ extern int __lll_timedwait_tid (int *, const struct timespec *)
>      __res;								      \
>    })
>
> +#ifdef ENABLE_LOCK_ELISION
> +extern int __lll_lock_elision (int *futex, short *adapt_count, int private)
> +  attribute_hidden;
> +
> +extern int __lll_unlock_elision(int *lock, int private)
> +  attribute_hidden;
> +
> +extern int __lll_trylock_elision(int *lock, short *adapt_count)
> +  attribute_hidden;
> +
> +# define lll_lock_elision(futex, adapt_count, private) \
> +  __lll_lock_elision (&(futex), &(adapt_count), private)
> +# define lll_unlock_elision(futex, private) \
> +  __lll_unlock_elision (&(futex), private)
> +# define lll_trylock_elision(futex, adapt_count) \
> +  __lll_trylock_elision(&(futex), &(adapt_count))
> +#endif
> +
>  #endif	/* lowlevellock.h */
> diff --git a/nptl/sysdeps/unix/sysv/linux/s390/pthread_mutex_cond_lock.c b/nptl/sysdeps/unix/sysv/linux/s390/pthread_mutex_cond_lock.c
> new file mode 100644
> index 0000000..6fc0f96
> --- /dev/null
> +++ b/nptl/sysdeps/unix/sysv/linux/s390/pthread_mutex_cond_lock.c
> @@ -0,0 +1,22 @@
> +/* Copyright (C) 2014 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/>.  */
> +
> +/* The cond lock is not actually elided yet, but we still need to handle
> +   already elided locks.  */
> +#include <elision-conf.h>
> +
> +#include <nptl/sysdeps/unix/sysv/linux/pthread_mutex_cond_lock.c>

Although the path to include differs, this is pretty much a copy of x86 version.  I think we
should consolidate both.

> diff --git a/nptl/sysdeps/unix/sysv/linux/s390/pthread_mutex_lock.c b/nptl/sysdeps/unix/sysv/linux/s390/pthread_mutex_lock.c
> new file mode 100644
> index 0000000..6fd6a98
> --- /dev/null
> +++ b/nptl/sysdeps/unix/sysv/linux/s390/pthread_mutex_lock.c
> @@ -0,0 +1,22 @@
> +/* Elided version of pthread_mutex_lock.
> +   Copyright (C) 2014 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/>.  */
> +
> +#include <elision-conf.h>
> +#include <force-elision.h>
> +
> +#include <nptl/pthread_mutex_lock.c>

Ditto.

> diff --git a/nptl/sysdeps/unix/sysv/linux/s390/pthread_mutex_timedlock.c b/nptl/sysdeps/unix/sysv/linux/s390/pthread_mutex_timedlock.c
> new file mode 100644
> index 0000000..d0e6537
> --- /dev/null
> +++ b/nptl/sysdeps/unix/sysv/linux/s390/pthread_mutex_timedlock.c
> @@ -0,0 +1,22 @@
> +/* Elided version of pthread_mutex_timedlock.
> +   Copyright (C) 2014 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/>.  */
> +
> +#include <elision-conf.h>
> +#include <force-elision.h>
> +
> +#include <nptl/pthread_mutex_timedlock.c>

Ditto.

> diff --git a/nptl/sysdeps/unix/sysv/linux/s390/pthread_mutex_trylock.c b/nptl/sysdeps/unix/sysv/linux/s390/pthread_mutex_trylock.c
> new file mode 100644
> index 0000000..ea8a8ff
> --- /dev/null
> +++ b/nptl/sysdeps/unix/sysv/linux/s390/pthread_mutex_trylock.c
> @@ -0,0 +1,22 @@
> +/* Elided version of pthread_mutex_trylock.
> +   Copyright (C) 2014 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/>.  */
> +
> +#include <elision-conf.h>
> +#include <force-elision.h>
> +
> +#include <nptl/pthread_mutex_trylock.c>

Ditto.

> diff --git a/nptl/sysdeps/unix/sysv/linux/s390/pthread_mutex_unlock.c b/nptl/sysdeps/unix/sysv/linux/s390/pthread_mutex_unlock.c
> new file mode 100644
> index 0000000..d244dca
> --- /dev/null
> +++ b/nptl/sysdeps/unix/sysv/linux/s390/pthread_mutex_unlock.c
> @@ -0,0 +1,19 @@
> +/* Elided version of pthread_mutex_trylock.
> +   Copyright (C) 2014 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/>.  */
> +
> +#include <nptl/pthread_mutex_unlock.c>

This file is not really doing anything, let sysdep dir build select the default one.

> diff --git a/sysdeps/s390/configure b/sysdeps/s390/configure
> index c2d05f7..6948cc2 100644
> --- a/sysdeps/s390/configure
> +++ b/sysdeps/s390/configure
> @@ -68,5 +68,41 @@ if test $ac_verc_fail = yes; then
>  fi
>
>
> +
> +{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for __builtin_tbegin" >&5
> +$as_echo_n "checking for __builtin_tbegin... " >&6; }
> +if ${libc_cv_gcc_builtin_tbegin+:} false; then :
> +  $as_echo_n "(cached) " >&6
> +else
> +  cat > conftest.c <<\EOF
> +#include <htmintrin.h>
> +void testtransaction ()
> +{
> +  if (__builtin_tbegin (0) == _HTM_TBEGIN_STARTED)
> +    {
> +      __builtin_tend ();
> +    }
> +}
> +EOF
> +if { ac_try='${CC-cc} -mhtm -O2 -S conftest.c -o - | grep -w tbegin > /dev/null'
> +  { { eval echo "\"\$as_me\":${as_lineno-$LINENO}: \"$ac_try\""; } >&5
> +  (eval $ac_try) 2>&5
> +  ac_status=$?
> +  $as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
> +  test $ac_status = 0; }; } ;
> +then
> +  libc_cv_gcc_builtin_tbegin=yes
> +else
> +  libc_cv_gcc_builtin_tbegin=no
> +fi
> +rm -f conftest*
> +fi
> +{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $libc_cv_gcc_builtin_tbegin" >&5
> +$as_echo "$libc_cv_gcc_builtin_tbegin" >&6; }
> +
> +if test "$enable_lock_elision" = yes && test "$libc_cv_gcc_builtin_tbegin" = no ; then
> +   critic_missing="$critic_missing The used GCC has no support for __builtin_tbegin, which is needed for lock-elision on target S390."
> +fi
> +
>  test -n "$critic_missing" && as_fn_error $? "
>  *** $critic_missing" "$LINENO" 5
> diff --git a/sysdeps/s390/configure.ac b/sysdeps/s390/configure.ac
> index 59cfdd1..493e9a4 100644
> --- a/sysdeps/s390/configure.ac
> +++ b/sysdeps/s390/configure.ac
> @@ -10,5 +10,31 @@ AC_CHECK_PROG_VER(AS, $AS, --version,
>  		  [GNU assembler.* \([0-9]*\.[0-9.]*\)],
>  		  [2.2[4-9]*|2.[3-9][0-9]*|[3-9].*|[1-9][0-9]*], critic_missing="$critic_missing The program AS is required in version >= 2.24 for target S390.")
>
> +
> +AC_CACHE_CHECK(for __builtin_tbegin, libc_cv_gcc_builtin_tbegin, [dnl
> +cat > conftest.c <<\EOF
> +#include <htmintrin.h>
> +void testtransaction ()
> +{
> +  if (__builtin_tbegin (0) == _HTM_TBEGIN_STARTED)
> +    {
> +      __builtin_tend ();
> +    }
> +}
> +EOF
> +dnl
> +dnl test, if the tbegin instruction is used by __builtin_tbegin
> +if AC_TRY_COMMAND([${CC-cc} -mhtm -O2 -S conftest.c -o - | grep -w tbegin > /dev/null]) ;
> +then
> +  libc_cv_gcc_builtin_tbegin=yes
> +else
> +  libc_cv_gcc_builtin_tbegin=no
> +fi
> +rm -f conftest* ])
> +
> +if test "$enable_lock_elision" = yes && test "$libc_cv_gcc_builtin_tbegin" = no ; then
> +   critic_missing="$critic_missing The used GCC has no support for __builtin_tbegin, which is needed for lock-elision on target S390."
> +fi
> +
>  test -n "$critic_missing" && AC_MSG_ERROR([
>  *** $critic_missing])
  

On Thu, 2014-04-24 at 17:54 -0300, Adhemerval Zanella wrote:
> On 24-04-2014 11:42, Stefan Liebler wrote:
> > +	  else
> > +	    {
> > +	      asm volatile ("" ::: "f0", "f1", "f2", "f3", "f4", "f5", "f6",
> > +			    "f7", "f8", "f9", "f10", "f11", "f12", "f13",
> > +			    "f14", "f15", "cc", "memory");
> 
> Just curious: why do you need this asm assembly? Some arch specific memory barrier? 

Unlike on Power, the S390 HTM doesn't rollback any changes to the FP
registers that were made in the failed transaction, so they have to
marked as clobbered.

Peter
  

On 04/24/2014 02:55 PM, Peter Bergner wrote:
> On Thu, 2014-04-24 at 17:54 -0300, Adhemerval Zanella wrote:
>> On 24-04-2014 11:42, Stefan Liebler wrote:
>>> +	  else
>>> +	    {
>>> +	      asm volatile ("" ::: "f0", "f1", "f2", "f3", "f4", "f5", "f6",
>>> +			    "f7", "f8", "f9", "f10", "f11", "f12", "f13",
>>> +			    "f14", "f15", "cc", "memory");
>>
>> Just curious: why do you need this asm assembly? Some arch specific memory barrier? 
> 
> Unlike on Power, the S390 HTM doesn't rollback any changes to the FP
> registers that were made in the failed transaction, so they have to
> marked as clobbered.

GCC takes care of adding clobbers as part of the tbegin builtin.

I see that it doesn't add the non-call-saved FPRs, which is exactly
what you're clobbering here.  But if this is in fact necessary, I
think you should really work that out with the compiler, rather than
leaving this hack here.



r~
  

Adhemerval Zanella <azanella@linux.vnet.ibm.com> writes:

> Hi Stefan
>
> I think the patch adds to much code duplication based on x86 version, it calls for 
> some refactoring.  Just comments below:

This was discussed some time ago.

The lock elision algorithms will likely evolve over time, and it's
doubtful they will change in the same ways for very different architectures

So I think it's better to keep it separated.

See it like everyone deserves their own optimized memcpy ...

-Andi
  

On 04/25/2014 12:14 AM, Richard Henderson wrote:
> On 04/24/2014 02:55 PM, Peter Bergner wrote:
>> On Thu, 2014-04-24 at 17:54 -0300, Adhemerval Zanella wrote:
>>> On 24-04-2014 11:42, Stefan Liebler wrote:
>>>> +	  else
>>>> +	    {
>>>> +	      asm volatile ("" ::: "f0", "f1", "f2", "f3", "f4", "f5", "f6",
>>>> +			    "f7", "f8", "f9", "f10", "f11", "f12", "f13",
>>>> +			    "f14", "f15", "cc", "memory");
>>>
>>> Just curious: why do you need this asm assembly? Some arch specific memory barrier? 
>>
>> Unlike on Power, the S390 HTM doesn't rollback any changes to the FP
>> registers that were made in the failed transaction, so they have to
>> marked as clobbered.
> 
> GCC takes care of adding clobbers as part of the tbegin builtin.
> 
> I see that it doesn't add the non-call-saved FPRs, which is exactly
> what you're clobbering here.  But if this is in fact necessary, I
> think you should really work that out with the compiler, rather than
> leaving this hack here.

The GCC builtin clobbers all FPRs. So I don't think the asm should be necessary at all. In fact it
probably doesn't even have the desired effect under all circumstances. GCC could decide to just wrap
the FPR save and restore operations around the inline asm.

cc is set by tbegin anyway. Mentioning it in the clobber list is not required.

The memory clobber might have been useful for cases where the transaction code does
non-transactional stores to values being read in the abort code. But we do not seem to have
something like this anymore.

-Andreas-