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[PATCH 02/11] Add the low level infrastructure for pthreads lock elision with TSX
- From: Andi Kleen <andi at firstfloor dot org>
- To: libc-alpha at sourceware dot org
- Cc: Andi Kleen <ak at linux dot jf dot intel dot com>
- Date: Tue, 11 Jun 2013 09:50:07 -0700
- Subject: [PATCH 02/11] Add the low level infrastructure for pthreads lock elision with TSX
- References: <1370969416-8337-1-git-send-email-andi at firstfloor dot org>
From: Andi Kleen <ak@linux.intel.com>
Lock elision using TSX is a technique to optimize lock scaling
It allows to run locks in parallel using hardware support for
a transactional execution mode in upcoming Intel CPUs.
See http://software.intel.com/file/41604 for the full
specification.
This patch implements a simple adaptive lock elision algorithm based
on RTM. It enables elision for the pthread mutexes and rwlocks.
The algorithm keeps track whether a mutex successfully elides or not,
and stops eliding for some time when it is not.
When the CPU supports RTM the elision path is automatically tried,
otherwise any elision is disabled.
The adaptation algorithm and its tuning is currently preliminary.
The code adds some checks to the lock fast paths. Micro-benchmarks
show little to no difference without RTM.
Lock elision can be enabled/disabled using environment variables.
It can be also enabled or disabled using new lock types for
mutex and rwlocks. The adaptation parameters are also tunable.
This patch implements the low level "lll_" code for lock elision.
Followon patches hook this into the pthread implement.
Changes with the RTM mutexes:
-----------------------------
Lock elision in pthreads is generally compatible with existing programs.
There are some obscure exceptions, which are expected to be uncommon.
See the manual for more details.
- A broken program that unlocks a free lock will crash.
There are ways around this with some tradeoffs (more code in hot paths)
This will also happen on systems without RTM with the patchkit.
I'm still undecided on what approach to take here; have to wait for testing reports.
- pthread_mutex_destroy of a lock mutex will not return EBUSY but 0.
- mutex appears free when elided.
pthread_mutex_lock(mutex);
if (pthread_mutex_trylock(mutex) != 0) do_something
will not do something when the lock elided.
However note that if the check is an assert it works as expected because the
assert failure aborts and the region is re-executed non transactionally,
with the old behaviour.
The same change applies to write locks for rwlocks.
[This is now only done for mutexes that have elision explicitely enabled,
standard mutexes abort in this situation]
- There's also a similar situation with trylock outside the mutex,
"knowing" that the mutex must be held due to some other condition.
In this case an assert failure cannot be recovered. This situation is
usually an existing bug in the program.
- Same applies to the rwlocks. Some of the return values changes
(for example there is no EDEADLK for an elided lock, unless it aborts.
However when elided it will also never deadlock of course)
- Timing changes, so broken programs that make assumptions about specific timing
may expose already existing latent problems. Note that these broken programs will
break in other situations too (loaded system, new faster hardware, compiler
optimizations etc.)
Currently elision is enabled by default on systems that support RTM,
unless explicitely disabled either in the program or by the user.
This patch implements the basic infrastructure for elision.
Open issues:
- XTEST or not XTEST in unlock, see above.
- Adaptation for rwlocks
- Condition variables don't use elision so far
- Adaptation tuning
2013-05-16 Andi Kleen <ak@linux.intel.com>
Hongjiu Lu <hongjiu.lu@intel.com>
* nptl-init.c (__pthread_force_elision): Add.
* pthreadP.h (__pthread_force_elision): Add.
* sysdeps/unix/sysv/linux/i386/lowlevellock.h (__lll_timedwait_tid,
lll_timedlock_elision, __lll_lock_elision, __lll_unlock_elision,
__lll_trylock_elision, lll_lock_elision, lll_unlock_elision,
lll_trylock_elision): Add.
* sysdeps/unix/sysv/linux/x86/Makefile: Imply x86
* sysdeps/unix/sysv/linux/x86/elision-conf.c: New file.
* sysdeps/unix/sysv/linux/x86/elision-conf.h: New file.
* sysdeps/unix/sysv/linux/x86/elision-lock.c: New file.
* sysdeps/unix/sysv/linux/x86/elision-timed.c: New file.
* sysdeps/unix/sysv/linux/x86/elision-trylock.c: New file.
* sysdeps/unix/sysv/linux/x86/elision-unlock.c: New file
* sysdeps/unix/sysv/linux/x86_64/lowlevellock.h (__lll_timedwait_tid,
lll_timedlock_elision, __lll_lock_elision, __lll_unlock_elision,
__lll_trylock_elision, lll_lock_elision, lll_unlock_elision,
lll_trylock_elision): Add.
* nptl/sysdeps/unix/sysv/linux/x86/hle.h: New file.
* elision-conf.h: New file.
---
nptl/elision-conf.h | 1 +
nptl/nptl-init.c | 2 +
nptl/pthreadP.h | 2 +
nptl/sysdeps/unix/sysv/linux/i386/lowlevellock.h | 22 +++
nptl/sysdeps/unix/sysv/linux/x86/Makefile | 3 +
nptl/sysdeps/unix/sysv/linux/x86/elision-conf.c | 211 +++++++++++++++++++++
nptl/sysdeps/unix/sysv/linux/x86/elision-conf.h | 53 ++++++
nptl/sysdeps/unix/sysv/linux/x86/elision-lock.c | 95 ++++++++++
nptl/sysdeps/unix/sysv/linux/x86/elision-timed.c | 8 +
nptl/sysdeps/unix/sysv/linux/x86/elision-trylock.c | 72 +++++++
nptl/sysdeps/unix/sysv/linux/x86/elision-unlock.c | 33 ++++
nptl/sysdeps/unix/sysv/linux/x86/hle.h | 75 ++++++++
nptl/sysdeps/unix/sysv/linux/x86_64/lowlevellock.h | 23 +++
13 files changed, 600 insertions(+)
create mode 100644 nptl/elision-conf.h
create mode 100644 nptl/sysdeps/unix/sysv/linux/x86/Makefile
create mode 100644 nptl/sysdeps/unix/sysv/linux/x86/elision-conf.c
create mode 100644 nptl/sysdeps/unix/sysv/linux/x86/elision-conf.h
create mode 100644 nptl/sysdeps/unix/sysv/linux/x86/elision-lock.c
create mode 100644 nptl/sysdeps/unix/sysv/linux/x86/elision-timed.c
create mode 100644 nptl/sysdeps/unix/sysv/linux/x86/elision-trylock.c
create mode 100644 nptl/sysdeps/unix/sysv/linux/x86/elision-unlock.c
create mode 100644 nptl/sysdeps/unix/sysv/linux/x86/hle.h
diff --git a/nptl/elision-conf.h b/nptl/elision-conf.h
new file mode 100644
index 0000000..40a8c17
--- /dev/null
+++ b/nptl/elision-conf.h
@@ -0,0 +1 @@
+/* empty */
diff --git a/nptl/nptl-init.c b/nptl/nptl-init.c
index 63fb729..1cc74e6 100644
--- a/nptl/nptl-init.c
+++ b/nptl/nptl-init.c
@@ -36,6 +36,8 @@
#include <lowlevellock.h>
#include <kernel-features.h>
+/* Force elision for all new locks. */
+int __pthread_force_elision attribute_hidden;
/* Size and alignment of static TLS block. */
size_t __static_tls_size;
diff --git a/nptl/pthreadP.h b/nptl/pthreadP.h
index fd52b07..31cae86 100644
--- a/nptl/pthreadP.h
+++ b/nptl/pthreadP.h
@@ -571,6 +571,8 @@ extern void __free_stacks (size_t limit) attribute_hidden;
extern void __wait_lookup_done (void) attribute_hidden;
+extern int __pthread_force_elision attribute_hidden;
+
#ifdef SHARED
# define PTHREAD_STATIC_FN_REQUIRE(name)
#else
diff --git a/nptl/sysdeps/unix/sysv/linux/i386/lowlevellock.h b/nptl/sysdeps/unix/sysv/linux/i386/lowlevellock.h
index f665ac9..cef9588 100644
--- a/nptl/sysdeps/unix/sysv/linux/i386/lowlevellock.h
+++ b/nptl/sysdeps/unix/sysv/linux/i386/lowlevellock.h
@@ -430,6 +430,12 @@ LLL_STUB_UNWIND_INFO_END
: "memory"); \
result; })
+extern int __lll_timedlock_elision (int *futex, short *try_lock,
+ const struct timespec *timeout,
+ int private) attribute_hidden;
+
+#define lll_timedlock_elision(futex, try_lock, timeout, private) \
+ __lll_timedlock_elision(&(futex), &(try_lock), timeout, private)
#define lll_robust_timedlock(futex, timeout, id, private) \
({ int result, ignore1, ignore2, ignore3; \
@@ -583,6 +589,22 @@ extern int __lll_timedwait_tid (int *tid, const struct timespec *abstime)
} \
__result; })
+extern int __lll_lock_elision (int *futex, short *try_lock, int private)
+ attribute_hidden;
+
+extern int __lll_unlock_elision(int *lock, int private)
+ attribute_hidden;
+
+extern int __lll_trylock_elision(int *lock, short *try_lock, int upgrade)
+ attribute_hidden;
+
+#define lll_lock_elision(futex, try_lock, private) \
+ __lll_lock_elision (&(futex), &(try_lock), private)
+#define lll_unlock_elision(futex, private) \
+ __lll_unlock_elision (&(futex), private)
+#define lll_trylock_elision(futex, try_lock, upgrade) \
+ __lll_trylock_elision(&(futex), &(try_lock), upgrade)
+
#endif /* !__ASSEMBLER__ */
#endif /* lowlevellock.h */
diff --git a/nptl/sysdeps/unix/sysv/linux/x86/Makefile b/nptl/sysdeps/unix/sysv/linux/x86/Makefile
new file mode 100644
index 0000000..61b7552
--- /dev/null
+++ b/nptl/sysdeps/unix/sysv/linux/x86/Makefile
@@ -0,0 +1,3 @@
+libpthread-sysdep_routines += init-arch
+libpthread-sysdep_routines += elision-lock elision-unlock elision-timed \
+ elision-trylock
diff --git a/nptl/sysdeps/unix/sysv/linux/x86/elision-conf.c b/nptl/sysdeps/unix/sysv/linux/x86/elision-conf.c
new file mode 100644
index 0000000..a7f5e15
--- /dev/null
+++ b/nptl/sysdeps/unix/sysv/linux/x86/elision-conf.c
@@ -0,0 +1,211 @@
+/* elision-conf.c: Lock elision tunable parameters.
+ Copyright (C) 2013 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 <sys/fcntl.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <init-arch.h>
+#include <elision-conf.h>
+#include <glibc-var.h>
+
+struct elision_config __elision_aconf =
+ {
+ .skip_lock_busy = 3,
+ .skip_lock_internal_abort = 3,
+ .retry_try_xbegin = 3,
+ .skip_trylock_internal_abort = 3,
+ };
+
+struct tune
+{
+ const char *name;
+ unsigned offset;
+ int len;
+};
+
+#define FIELD(x) { #x, offsetof(struct elision_config, x), sizeof(#x)-1 }
+
+static const struct tune tunings[] =
+ {
+ FIELD(skip_lock_busy),
+ FIELD(skip_lock_internal_abort),
+ FIELD(retry_try_xbegin),
+ FIELD(skip_trylock_internal_abort),
+ {}
+ };
+
+#define PAIR(x) x, sizeof (x)-1
+
+/* Complain. */
+
+static void
+complain (const char *msg, int len)
+{
+ INTERNAL_SYSCALL_DECL (err);
+ INTERNAL_SYSCALL (write, err, 3, 2, (char *)msg, len);
+}
+
+/* Parse configuration information. */
+
+static void
+elision_aconf_setup (const char *s)
+{
+ int i;
+
+ while (*s)
+ {
+ for (i = 0; tunings[i].name != NULL; i++)
+ {
+ int nlen = tunings[i].len;
+
+ if (strncmp (tunings[i].name, s, nlen) == 0)
+ {
+ char *end;
+ int val;
+
+ if (s[nlen] != '=')
+ {
+ complain (PAIR ("pthreads: invalid GLIBC_PTHREAD_MUTEX syntax: missing =\n"));
+ return;
+ }
+ s += nlen + 1;
+ val = strtoul (s, &end, 0);
+ if (end == s)
+ {
+ complain (PAIR ("pthreads: invalid GLIBC_PTHREAD_MUTEX syntax: missing number\n"));
+ return;
+ }
+ *(int *)(((char *)&__elision_aconf) + tunings[i].offset) = val;
+ s = end;
+ if (*s == ',' || *s == ':')
+ s++;
+ else if (*s)
+ {
+ complain (PAIR ("pthreads: invalid GLIBC_PTHREAD_MUTEX syntax: garbage after number\n"));
+ return;
+ }
+ break;
+ }
+ }
+ if (tunings[i].name == NULL)
+ {
+ complain (PAIR ("pthreads: invalid GLIBC_PTHREAD_MUTEX syntax: unknown tunable\n"));
+ return;
+ }
+ }
+}
+
+/* Elided rwlock toggle. */
+
+int __rwlock_rtm_enabled attribute_hidden;
+
+/* Retries for elided rwlocks. */
+
+int __rwlock_rtm_read_retries attribute_hidden = 3;
+
+/* Global elision check switch. */
+
+int __elision_available attribute_hidden;
+
+/* Initialize elision mutex. */
+
+static void
+elision_mutex_init (const char *s)
+{
+ if (s == NULL)
+ {
+ __pthread_force_elision = __elision_available;
+ return;
+ }
+
+ if (strncmp (s, "adaptive", 8) == 0 && (s[8] == 0 || s[8] == ':'))
+ {
+ __pthread_force_elision = __elision_available;
+ if (s[8] == ':')
+ elision_aconf_setup (s + 9);
+ }
+ else if (strncmp (s, "elision", 7) == 0 && (s[7] == 0 || s[7] == ':'))
+ {
+ __pthread_force_elision = __elision_available;
+ if (s[7] == ':')
+ elision_aconf_setup (s + 8);
+ }
+ else if (strncmp (s, "none", 4) == 0 && s[4] == 0)
+ __pthread_force_elision = 0;
+ else
+ complain (PAIR ("pthreads: Unknown setting for GLIBC_PTHREAD_MUTEX\n"));
+}
+
+/* Initialize elision rwlock. */
+
+static void
+elision_rwlock_init (const char *s)
+{
+ if (s == NULL)
+ {
+ __rwlock_rtm_enabled = __elision_available;
+ return;
+ }
+ if (strncmp (s, "elision", 7) == 0)
+ {
+ __rwlock_rtm_enabled = __elision_available;
+ if (s[7] == ':')
+ {
+ char *end;
+ int n;
+
+ n = strtoul (s + 8, &end, 0);
+ if (end == s + 8)
+ complain (PAIR ("pthreads: Bad retry number for GLIBC_PTHREAD_RWLOCK\n"));
+ else
+ __rwlock_rtm_read_retries = n;
+ }
+ }
+ else if (strcmp (s, "none") == 0)
+ __rwlock_rtm_enabled = 0;
+ else
+ complain (PAIR ("pthreads: Unknown setting for GLIBC_PTHREAD_RWLOCK\n"));
+}
+
+/* Initialize elison. */
+
+static void
+elision_init (int argc __attribute__ ((unused)),
+ char **argv __attribute__ ((unused)),
+ char **environ)
+{
+ __elision_available = HAS_RTM;
+
+ /* For static builds need to call this explicitely. Noop for dynamic. */
+ __glibc_var_init (argc, argv, environ);
+ elision_mutex_init (_dl_glibc_var[GLIBC_VAR_PTHREAD_MUTEX].val);
+ elision_rwlock_init (_dl_glibc_var[GLIBC_VAR_PTHREAD_RWLOCK].val);
+}
+
+#ifdef SHARED
+# define INIT_SECTION ".init_array"
+#else
+# define INIT_SECTION ".preinit_array"
+#endif
+
+void (*const __pthread_init_array []) (int, char **, char **)
+ __attribute__ ((section (INIT_SECTION), aligned (sizeof (void *)))) =
+{
+ &elision_init
+};
diff --git a/nptl/sysdeps/unix/sysv/linux/x86/elision-conf.h b/nptl/sysdeps/unix/sysv/linux/x86/elision-conf.h
new file mode 100644
index 0000000..9a540b9
--- /dev/null
+++ b/nptl/sysdeps/unix/sysv/linux/x86/elision-conf.h
@@ -0,0 +1,53 @@
+/* elision-conf.h: Lock elision tunable parameters.
+ Copyright (C) 2013 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/>. */
+#ifndef _ELISION_CONF_H
+#define _ELISION_CONF_H 1
+
+#include <pthread.h>
+#include <cpuid.h>
+#include <time.h>
+
+/* Should make sure there is no false sharing on this. */
+
+struct elision_config
+{
+ int skip_lock_busy;
+ int skip_lock_internal_abort;
+ int retry_try_xbegin;
+ int skip_trylock_internal_abort;
+};
+
+extern struct elision_config __elision_aconf attribute_hidden;
+
+extern int __rwlock_rtm_enabled;
+extern int __elision_available;
+
+extern int __pthread_mutex_timedlock_nortm (pthread_mutex_t *mutex, const struct timespec *);
+extern int __pthread_mutex_timedlock_rtm (pthread_mutex_t *mutex, const struct timespec *);
+extern int __pthread_mutex_timedlock (pthread_mutex_t *mutex, const struct timespec *);
+extern int __pthread_mutex_lock_nortm (pthread_mutex_t *mutex);
+extern int __pthread_mutex_lock_rtm (pthread_mutex_t *mutex);
+extern int __pthread_mutex_lock (pthread_mutex_t *mutex);
+extern int __pthread_mutex_trylock_nortm (pthread_mutex_t *);
+extern int __pthread_mutex_trylock_rtm (pthread_mutex_t *);
+extern int __pthread_mutex_trylock (pthread_mutex_t *);
+
+/* Tell the test suite to test elision for this architecture. */
+#define HAVE_ELISION 1
+
+#endif
diff --git a/nptl/sysdeps/unix/sysv/linux/x86/elision-lock.c b/nptl/sysdeps/unix/sysv/linux/x86/elision-lock.c
new file mode 100644
index 0000000..faffe78
--- /dev/null
+++ b/nptl/sysdeps/unix/sysv/linux/x86/elision-lock.c
@@ -0,0 +1,95 @@
+/* elision-lock.c: Elided pthread mutex lock.
+ Copyright (C) 2011, 2012, 2013 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 "hle.h"
+#include <elision-conf.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 *try_lock, EXTRAARG int private)
+{
+ if (*try_lock <= 0)
+ {
+ unsigned status;
+ int try_xbegin;
+
+ for (try_xbegin = aconf.retry_try_xbegin;
+ try_xbegin > 0;
+ try_xbegin--)
+ {
+ if ((status = _xbegin()) == _XBEGIN_STARTED)
+ {
+ if (*futex == 0)
+ return 0;
+
+ /* Lock was busy. Fall back to normal locking.
+ Could also _xend here but xabort with 0xff code
+ is more visible in the profiler. */
+ _xabort (_ABORT_LOCK_BUSY);
+ }
+
+ if (!(status & _XABORT_RETRY))
+ {
+ if ((status & _XABORT_EXPLICIT)
+ && _XABORT_CODE (status) == _ABORT_LOCK_BUSY)
+ {
+ /* Right now we skip here. Better would be to wait a bit
+ and retry. This likely needs some spinning. */
+ if (*try_lock != aconf.skip_lock_busy)
+ *try_lock = aconf.skip_lock_busy;
+ }
+ /* Internal abort. There is no chance for retry.
+ Use the normal locking and next time use lock.
+ Be careful to avoid writing to the lock. */
+ else if (*try_lock != aconf.skip_lock_internal_abort)
+ *try_lock = aconf.skip_lock_internal_abort;
+ break;
+ }
+ }
+ }
+ else
+ {
+ /* Use a normal lock until the threshold counter runs out.
+ Lost updates possible. */
+ (*try_lock)--;
+ }
+
+ /* Use a normal lock here. */
+ return LLL_LOCK ((*futex), private);
+}
diff --git a/nptl/sysdeps/unix/sysv/linux/x86/elision-timed.c b/nptl/sysdeps/unix/sysv/linux/x86/elision-timed.c
new file mode 100644
index 0000000..3e95623
--- /dev/null
+++ b/nptl/sysdeps/unix/sysv/linux/x86/elision-timed.c
@@ -0,0 +1,8 @@
+#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/x86/elision-trylock.c b/nptl/sysdeps/unix/sysv/linux/x86/elision-trylock.c
new file mode 100644
index 0000000..97b13b3
--- /dev/null
+++ b/nptl/sysdeps/unix/sysv/linux/x86/elision-trylock.c
@@ -0,0 +1,72 @@
+/* elision-trylock.c: Lock eliding trylock for pthreads.
+ Copyright (C) 2013 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 "hle.h"
+#include <elision-conf.h>
+
+#define aconf __elision_aconf
+
+/* Try to elide a futex trylock. FUTEX is the futex variable. TRY_LOCK is the
+ adaptation counter in the mutex. UPGRADED is != 0 when this is for an
+ automatically upgraded lock. */
+
+int
+__lll_trylock_elision (int *futex, short *try_lock, int upgraded)
+{
+ /* Only try a transaction if it's worth it. */
+ if (*try_lock <= 0)
+ {
+ unsigned status;
+
+ /* When this could be a nested trylock that is not explicitely
+ declared an elided lock abort. This makes us follow POSIX
+ paper semantics. */
+ if (upgraded)
+ _xabort (_ABORT_NESTED_TRYLOCK);
+
+ if ((status = _xbegin()) == _XBEGIN_STARTED)
+ {
+ if (*futex == 0)
+ return 0;
+
+ /* Lock was busy. Fall back to normal locking.
+ Could also _xend here but xabort with 0xff code
+ is more visible in the profiler. */
+ _xabort (_ABORT_LOCK_BUSY);
+ }
+
+ if (!(status & _XABORT_RETRY))
+ {
+ /* Internal abort. No chance for retry. For future
+ locks don't try speculation for some time. */
+ if (*try_lock != aconf.skip_trylock_internal_abort)
+ *try_lock = aconf.skip_trylock_internal_abort;
+ }
+ /* Could do some retries here. */
+ }
+ else
+ {
+ /* Lost updates are possible, but harmless. */
+ (*try_lock)--;
+ }
+
+ return lll_trylock (*futex);
+}
diff --git a/nptl/sysdeps/unix/sysv/linux/x86/elision-unlock.c b/nptl/sysdeps/unix/sysv/linux/x86/elision-unlock.c
new file mode 100644
index 0000000..bb13c6b
--- /dev/null
+++ b/nptl/sysdeps/unix/sysv/linux/x86/elision-unlock.c
@@ -0,0 +1,33 @@
+/* elision-unlock.c: Commit an elided pthread lock.
+ Copyright (C) 2013 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"
+#include "hle.h"
+
+int
+__lll_unlock_elision(int *lock, int private)
+{
+ /* When the lock was free we're in a transaction.
+ When you crash here you unlocked a free lock. */
+ if (*lock == 0)
+ _xend();
+ else
+ lll_unlock ((*lock), private);
+ return 0;
+}
diff --git a/nptl/sysdeps/unix/sysv/linux/x86/hle.h b/nptl/sysdeps/unix/sysv/linux/x86/hle.h
new file mode 100644
index 0000000..a08f0fa
--- /dev/null
+++ b/nptl/sysdeps/unix/sysv/linux/x86/hle.h
@@ -0,0 +1,75 @@
+/* Shared RTM header. Emulate TSX intrinsics for compilers and assemblers
+ that do not support the intrinsics and instructions yet. */
+#ifndef _HLE_H
+#define _HLE_H 1
+
+#ifdef __ASSEMBLER__
+
+.macro XBEGIN target
+ .byte 0xc7,0xf8
+ .long \target-1f
+1:
+.endm
+
+.macro XEND
+ .byte 0x0f,0x01,0xd5
+.endm
+
+.macro XABORT code
+ .byte 0xc6,0xf8,\code
+.endm
+
+.macro XTEST
+ .byte 0x0f,0x01,0xd6
+.endm
+
+#endif
+
+/* Official RTM intrinsics interface matching gcc/icc, but works
+ on older gcc compatible compilers and binutils.
+ We should somehow detect if the compiler supports it, because
+ it may be able to generate slightly better code. */
+
+#define _XBEGIN_STARTED (~0u)
+#define _XABORT_EXPLICIT (1 << 0)
+#define _XABORT_RETRY (1 << 1)
+#define _XABORT_CONFLICT (1 << 2)
+#define _XABORT_CAPACITY (1 << 3)
+#define _XABORT_DEBUG (1 << 4)
+#define _XABORT_NESTED (1 << 5)
+#define _XABORT_CODE(x) (((x) >> 24) & 0xff)
+
+#define _ABORT_LOCK_BUSY 0xff
+#define _ABORT_LOCK_IS_LOCKED 0xfe
+#define _ABORT_NESTED_TRYLOCK 0xfd
+
+#ifndef __ASSEMBLER__
+
+#define __force_inline __attribute__((__always_inline__)) inline
+
+static __force_inline int _xbegin(void)
+{
+ int ret = _XBEGIN_STARTED;
+ asm volatile (".byte 0xc7,0xf8 ; .long 0" : "+a" (ret) :: "memory");
+ return ret;
+}
+
+static __force_inline void _xend(void)
+{
+ asm volatile (".byte 0x0f,0x01,0xd5" ::: "memory");
+}
+
+static __force_inline void _xabort(const unsigned int status)
+{
+ asm volatile (".byte 0xc6,0xf8,%P0" :: "i" (status) : "memory");
+}
+
+static __force_inline int _xtest(void)
+{
+ unsigned char out;
+ asm volatile (".byte 0x0f,0x01,0xd6 ; setnz %0" : "=r" (out) :: "memory");
+ return out;
+}
+
+#endif
+#endif
diff --git a/nptl/sysdeps/unix/sysv/linux/x86_64/lowlevellock.h b/nptl/sysdeps/unix/sysv/linux/x86_64/lowlevellock.h
index 7a176ae..6f0a886 100644
--- a/nptl/sysdeps/unix/sysv/linux/x86_64/lowlevellock.h
+++ b/nptl/sysdeps/unix/sysv/linux/x86_64/lowlevellock.h
@@ -427,6 +427,13 @@ LLL_STUB_UNWIND_INFO_END
: "memory", "cx", "cc", "r10", "r11"); \
result; })
+extern int __lll_timedlock_elision (int *futex, short *try_lock,
+ const struct timespec *timeout,
+ int private) attribute_hidden;
+
+#define lll_timedlock_elision(futex, try_lock, timeout, private) \
+ __lll_timedlock_elision(&(futex), &(try_lock), timeout, private)
+
#define lll_robust_timedlock(futex, timeout, id, private) \
({ int result, ignore1, ignore2, ignore3; \
__asm __volatile (LOCK_INSTR "cmpxchgl %1, %4\n\t" \
@@ -597,6 +604,22 @@ extern int __lll_timedwait_tid (int *tid, const struct timespec *abstime)
} \
__result; })
+extern int __lll_lock_elision (int *futex, short *try_lock, int private)
+ attribute_hidden;
+
+extern int __lll_unlock_elision (int *lock, int private)
+ attribute_hidden;
+
+extern int __lll_trylock_elision (int *lock, short *try_lock, int upgraded)
+ attribute_hidden;
+
+#define lll_lock_elision(futex, try_lock, private) \
+ __lll_lock_elision (&(futex), &(try_lock), private)
+#define lll_unlock_elision(futex, private) \
+ __lll_unlock_elision (&(futex), private)
+#define lll_trylock_elision(futex, try_lock, upgraded) \
+ __lll_trylock_elision (&(futex), &(try_lock), upgraded)
+
#endif /* !__ASSEMBLER__ */
#endif /* lowlevellock.h */
--
1.8.1.4