Add generic versions of pthread_spin_lock and pthread_spin_trylock.

14 files changed, 123 insertions, 166 deletions

diff --git a/nptl/ChangeLog b/nptl/ChangeLog
index 1deaa6a276..0f31b4dbe4 100644
--- a/nptl/ChangeLog
+++ b/nptl/ChangeLog
@@ -1,3 +1,8 @@
+2012-08-15  Maxim Kuvyrkov  <maxim@codesourcery.com>
+
+	* pthread_spin_lock.c: New file.
+	* pthread_spin_trylock.c: New file.
+
 2012-08-08  Joseph Myers  <joseph@codesourcery.com>
 
 	* allocatestack.c (setxid_signal_thread) [__ASSUME_TGKILL]: Make
diff --git a/nptl/pthread_spin_lock.c b/nptl/pthread_spin_lock.c
new file mode 100644
index 0000000000..91733fb7f1
--- /dev/null
+++ b/nptl/pthread_spin_lock.c
@@ -0,0 +1,69 @@
+/* pthread_spin_lock -- lock a spin lock.  Generic version.
+   Copyright (C) 2012 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 <atomic.h>
+#include "pthreadP.h"
+
+/* A machine-specific version can define SPIN_LOCK_READS_BETWEEN_CMPXCHG
+  to the number of plain reads that it's optimal to spin on between uses
+  of atomic_compare_and_exchange_val_acq.  If spinning forever is optimal
+  then use -1.  If no plain reads here would ever be optimal, use 0.  */
+#ifndef SPIN_LOCK_READS_BETWEEN_CMPXCHG
+# warning machine-dependent file should define SPIN_LOCK_READS_BETWEEN_CMPXCHG
+# define SPIN_LOCK_READS_BETWEEN_CMPXCHG 1000
+#endif
+
+int
+pthread_spin_lock (pthread_spinlock_t *lock)
+{
+  /* atomic_exchange usually takes less instructions than
+     atomic_compare_and_exchange.  On the other hand,
+     atomic_compare_and_exchange potentially generates less bus traffic
+     when the lock is locked.
+     We assume that the first try mostly will be successful, and we use
+     atomic_exchange.  For the subsequent tries we use
+     atomic_compare_and_exchange.  */
+  if (atomic_exchange_acq (lock, 1) == 0)
+    return 0;
+
+  do
+    {
+      /* The lock is contended and we need to wait.  Going straight back
+	 to cmpxchg is not a good idea on many targets as that will force
+	 expensive memory synchronizations among processors and penalize other
+	 running threads.
+	 On the other hand, we do want to update memory state on the local core
+	 once in a while to avoid spinning indefinitely until some event that
+	 will happen to update local memory as a side-effect.  */
+      if (SPIN_LOCK_READS_BETWEEN_CMPXCHG >= 0)
+	{
+	  int wait = SPIN_LOCK_READS_BETWEEN_CMPXCHG;
+
+	  while (*lock != 0 && wait > 0)
+	    --wait;
+	}
+      else
+	{
+	  while (*lock != 0)
+	    ;
+	}
+    }
+  while (atomic_compare_and_exchange_val_acq (lock, 1, 0) != 0);
+
+  return 0;
+}
diff --git a/ports/sysdeps/arm/nptl/pthread_spin_trylock.c b/nptl/pthread_spin_trylock.c
index 7d3118071e..db9372cb58 100644
--- a/ports/sysdeps/arm/nptl/pthread_spin_trylock.c
+++ b/nptl/pthread_spin_trylock.c
@@ -1,4 +1,5 @@
-/* Copyright (C) 2008 Free Software Foundation, Inc.
+/* pthread_spin_trylock -- trylock a spin lock.  Generic version.
+   Copyright (C) 2012 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
@@ -12,7 +13,7 @@
    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
+   License along with the GNU C Library; if not, see
    <http://www.gnu.org/licenses/>.  */
 
 #include <errno.h>
@@ -22,5 +23,5 @@
 int
 pthread_spin_trylock (pthread_spinlock_t *lock)
 {
-  return atomic_compare_and_exchange_val_acq (lock, 1, 0) ? EBUSY : 0;
+  return atomic_exchange_acq (lock, 1) ? EBUSY : 0;
 }
diff --git a/ports/ChangeLog.arm b/ports/ChangeLog.arm
index bb38c15398..359bd0d68a 100644
--- a/ports/ChangeLog.arm
+++ b/ports/ChangeLog.arm
@@ -1,3 +1,8 @@
+2012-08-15  Maxim Kuvyrkov  <maxim@codesourcery.com>
+
+	* sysdeps/arm/nptl/pthread_spin_lock.c: Use generic code.
+	* sysdeps/arm/nptl/pthread_spin_trylock.c: Remove, use generic version.
+
 2012-08-14  Roland McGrath  <roland@hack.frob.com>
 
 	* sysdeps/unix/sysv/linux/arm/nptl/bits/atomic.h: Renamed to ...
diff --git a/ports/ChangeLog.hppa b/ports/ChangeLog.hppa
index 0501211127..a28fbceb37 100644
--- a/ports/ChangeLog.hppa
+++ b/ports/ChangeLog.hppa
@@ -1,3 +1,8 @@
+2012-08-15  Maxim Kuvyrkov  <maxim@codesourcery.com>
+
+	* sysdeps/hppa/nptl/pthread_spin_lock.c: Use generic code.
+	* sysdeps/hppa/nptl/pthread_spin_trylock.c: Remove, use generic version.
+
 2012-08-12  Mike Frysinger  <vapier@gentoo.org>
 
 	* sysdeps/unix/sysv/linux/hppa/syscalls.list: Add prlimit64.
diff --git a/ports/ChangeLog.m68k b/ports/ChangeLog.m68k
index 9fc9d387f4..62a8eb3bb6 100644
--- a/ports/ChangeLog.m68k
+++ b/ports/ChangeLog.m68k
@@ -1,3 +1,8 @@
+2012-08-15  Maxim Kuvyrkov  <maxim@codesourcery.com>
+
+	* sysdeps/m68k/nptl/pthread_spin_lock.c: Use generic code.
+	* sysdeps/m68k/nptl/pthread_spin_trylock.c: Remove, use generic version.
+
 2012-08-10  Andreas Schwab  <schwab@linux-m68k.org>
 
 	* sysdeps/m68k/ldsodefs.h (m68k_gnu_pltenter): Remove const on
diff --git a/ports/ChangeLog.mips b/ports/ChangeLog.mips
index b69846f996..518777223c 100644
--- a/ports/ChangeLog.mips
+++ b/ports/ChangeLog.mips
@@ -1,3 +1,9 @@
+2012-08-15  Maxim Kuvyrkov  <maxim@codesourcery.com>
+
+	* sysdeps/mips/nptl/pthread_spin_lock.S: Remove, use generic version.
+	* sysdeps/mips/nptl/pthread_spin_lock.c: New file.
+	* sysdeps/mips/nptl/pthread_spin_trylock.S: Remove, use generic version.
+
 2012-08-15  Joseph Myers  <joseph@codesourcery.com>
 
 	* sysdeps/mips/dl-lookup.c: Update from generic version.
diff --git a/ports/sysdeps/arm/nptl/pthread_spin_lock.c b/ports/sysdeps/arm/nptl/pthread_spin_lock.c
index 3a23bd31a5..4f81571735 100644
--- a/ports/sysdeps/arm/nptl/pthread_spin_lock.c
+++ b/ports/sysdeps/arm/nptl/pthread_spin_lock.c
@@ -1,4 +1,4 @@
-/* Copyright (C) 2008 Free Software Foundation, Inc.
+/* Copyright (C) 2008-2012 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
@@ -15,15 +15,9 @@
    License along with the GNU C Library.  If not, see
    <http://www.gnu.org/licenses/>.  */
 
-#include <atomic.h>
-#include "pthreadP.h"
+#define SPIN_LOCK_READS_BETWEEN_CMPXCHG 1000
 
-int
-pthread_spin_lock (pthread_spinlock_t *lock)
-{
-  while (atomic_compare_and_exchange_val_acq (lock, 1, 0) != 0)
-   while (*lock != 0)
-    ;
-
-  return 0;
-}
+/* We can't use the normal "#include <nptl/pthread_spin_lock.c>" because
+   it will resolve to this very file.  Using "sysdeps/.." as reference to the
+   top level directory does the job.  */
+#include <sysdeps/../nptl/pthread_spin_lock.c>
diff --git a/ports/sysdeps/hppa/nptl/pthread_spin_lock.c b/ports/sysdeps/hppa/nptl/pthread_spin_lock.c
index bcf22408da..e011853130 100644
--- a/ports/sysdeps/hppa/nptl/pthread_spin_lock.c
+++ b/ports/sysdeps/hppa/nptl/pthread_spin_lock.c
@@ -1,4 +1,4 @@
-/* Copyright (C) 2005 Free Software Foundation, Inc.
+/* Copyright (C) 2005-2012 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
@@ -15,23 +15,9 @@
    License along with the GNU C Library.  If not, see
    <http://www.gnu.org/licenses/>.  */
 
-#include <atomic.h>
-#include "pthreadP.h"
+#define SPIN_LOCK_READS_BETWEEN_CMPXCHG 1000
 
-int
-pthread_spin_lock (pthread_spinlock_t *lock)
-{
-#if 0
-  volatile unsigned int *addr = __ldcw_align (lock);
-
-  while (__ldcw (addr) == 0)
-    while (*addr == 0) ;
-
-  return 0;
-#endif
-
-  while (atomic_compare_and_exchange_val_acq(lock, 1, 0) == 1)
-    while (*lock == 1);
-  
-  return 0;
-}
+/* We can't use the normal "#include <nptl/pthread_spin_lock.c>" because
+   it will resolve to this very file.  Using "sysdeps/.." as reference to the
+   top level directory does the job.  */
+#include <sysdeps/../nptl/pthread_spin_lock.c>
diff --git a/ports/sysdeps/hppa/nptl/pthread_spin_trylock.c b/ports/sysdeps/hppa/nptl/pthread_spin_trylock.c
deleted file mode 100644
index a802861012..0000000000
--- a/ports/sysdeps/hppa/nptl/pthread_spin_trylock.c
+++ /dev/null
@@ -1,33 +0,0 @@
-/* Copyright (C) 2005 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 <errno.h>
-#include <atomic.h>
-#include "pthreadP.h"
-
-int
-pthread_spin_trylock (pthread_spinlock_t *lock)
-{
-#if 0
-  volatile unsigned int *a = __ldcw_align (lock);
-
-  return __ldcw (a) ? 0 : EBUSY;
-#endif
-
-  return atomic_compare_and_exchange_val_acq(lock, 1, 0) ? EBUSY : 0;
-
-}
diff --git a/ports/sysdeps/m68k/nptl/pthread_spin_lock.c b/ports/sysdeps/m68k/nptl/pthread_spin_lock.c
index 90a8262b24..2616a7f2a2 100644
--- a/ports/sysdeps/m68k/nptl/pthread_spin_lock.c
+++ b/ports/sysdeps/m68k/nptl/pthread_spin_lock.c
@@ -1,4 +1,4 @@
-/* Copyright (C) 2010 Free Software Foundation, Inc.
+/* Copyright (C) 2010-2012 Free Software Foundation, Inc.
    This file is part of the GNU C Library.
    Contributed by Maxim Kuvyrkov <maxim@codesourcery.com>, 2010.
 
@@ -16,15 +16,9 @@
    License along with the GNU C Library.  If not, see
    <http://www.gnu.org/licenses/>.  */
 
-#include <atomic.h>
-#include "pthreadP.h"
+#define SPIN_LOCK_READS_BETWEEN_CMPXCHG 1000
 
-int
-pthread_spin_lock (pthread_spinlock_t *lock)
-{
-  while (atomic_compare_and_exchange_val_acq(lock, 1, 0) != 0)
-   while (*lock != 0)
-    ;
-
-  return 0;
-}
+/* We can't use the normal "#include <nptl/pthread_spin_lock.c>" because
+   it will resolve to this very file.  Using "sysdeps/.." as reference to the
+   top level directory does the job.  */
+#include <sysdeps/../nptl/pthread_spin_lock.c>
diff --git a/ports/sysdeps/mips/nptl/pthread_spin_lock.S b/ports/sysdeps/mips/nptl/pthread_spin_lock.S
deleted file mode 100644
index a8504f1636..0000000000
--- a/ports/sysdeps/mips/nptl/pthread_spin_lock.S
+++ /dev/null
@@ -1,36 +0,0 @@
-/* Copyright (C) 2005 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 <sys/asm.h>
-#include <sysdep.h>
-#include <sgidefs.h>
-
-ENTRY (pthread_spin_lock)
-	.set	push
-#if _MIPS_SIM == _ABIO32
-	.set	mips2
-#endif
-1:	ll	a2, 0(a0)
-	li	a1, 1
-	bnez	a2, 1b
-	sc	a1, 0(a0)
-	beqz	a1, 1b
-	MIPS_SYNC
-	.set	pop
-	li	v0, 0
-	ret
-PSEUDO_END (pthread_spin_lock)
diff --git a/ports/sysdeps/m68k/nptl/pthread_spin_trylock.c b/ports/sysdeps/mips/nptl/pthread_spin_lock.c
index f4b0c0d0a3..f39b0182bc 100644
--- a/ports/sysdeps/m68k/nptl/pthread_spin_trylock.c
+++ b/ports/sysdeps/mips/nptl/pthread_spin_lock.c
@@ -1,6 +1,5 @@
-/* Copyright (C) 2010 Free Software Foundation, Inc.
+/* Copyright (C) 2012 Free Software Foundation, Inc.
    This file is part of the GNU C Library.
-   Contributed by Maxim Kuvyrkov <maxim@codesourcery.com>, 2010.
 
    The GNU C Library is free software; you can redistribute it and/or
    modify it under the terms of the GNU Lesser General Public
@@ -16,12 +15,9 @@
    License along with the GNU C Library.  If not, see
    <http://www.gnu.org/licenses/>.  */
 
-#include <errno.h>
-#include <atomic.h>
-#include "pthreadP.h"
+#define SPIN_LOCK_READS_BETWEEN_CMPXCHG 1000
 
-int
-pthread_spin_trylock (pthread_spinlock_t *lock)
-{
-  return atomic_compare_and_exchange_val_acq(lock, 1, 0) ? EBUSY : 0;
-}
+/* We can't use the normal "#include <nptl/pthread_spin_lock.c>" because
+   it will resolve to this very file.  Using "sysdeps/.." as reference to the
+   top level directory does the job.  */
+#include <sysdeps/../nptl/pthread_spin_lock.c>
diff --git a/ports/sysdeps/mips/nptl/pthread_spin_trylock.S b/ports/sysdeps/mips/nptl/pthread_spin_trylock.S
deleted file mode 100644
index 95b55c3d4e..0000000000
--- a/ports/sysdeps/mips/nptl/pthread_spin_trylock.S
+++ /dev/null
@@ -1,40 +0,0 @@
-/* Copyright (C) 2005 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 <sys/asm.h>
-#include <sysdep.h>
-#define _ERRNO_H 1
-#include <bits/errno.h>
-#include <sgidefs.h>
-
-ENTRY (pthread_spin_trylock)
-	.set	push
-#if _MIPS_SIM == _ABIO32
-	.set	mips2
-#endif
-	ll	a2, 0(a0)
-	li	a1, 1
-	bnez	a2, 1f
-	sc	a1, 0(a0)
-	beqz	a1, 1f
-	MIPS_SYNC
-	.set	pop
-	li	v0, 0
-	ret
-1:	li	v0, EBUSY
-	ret
-PSEUDO_END (pthread_spin_trylock)