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Optimize __libc_lock_lock and __libc_lock_trylock for MIPS.

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This commit is contained in:
Maxim Kuvyrkov 2012-08-15 16:44:30 -07:00
parent ef4009734b
commit 309becf120
4 changed files with 57 additions and 4 deletions
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6
nptl/ChangeLog
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@ -1,3 +1,9 @@
2012-08-15 Tom de Vries <vries@codesourcery.com>
Maxim Kuvyrkov <maxim@codesourcery.com>
* sysdeps/pthread/bits/libc-lockP.h (__libc_lock_lock)
(__libc_lock_trylock): Allow pre-existing definitions.
2012-08-15 Maxim Kuvyrkov <maxim@codesourcery.com>
* pthread_spin_lock.c: New file.

10
nptl/sysdeps/pthread/bits/libc-lockP.h
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@ -176,9 +176,12 @@ typedef pthread_key_t __libc_key_t;
/* Lock the named lock variable. */
#if !defined NOT_IN_libc || defined IS_IN_libpthread
# define __libc_lock_lock(NAME) \
# ifndef __libc_lock_lock
# define __libc_lock_lock(NAME) \
({ lll_lock (NAME, LLL_PRIVATE); 0; })
# endif
#else
# undef __libc_lock_lock
# define __libc_lock_lock(NAME) \
__libc_maybe_call (__pthread_mutex_lock, (&(NAME)), 0)
#endif
@ -189,9 +192,12 @@ typedef pthread_key_t __libc_key_t;
/* Try to lock the named lock variable. */
#if !defined NOT_IN_libc || defined IS_IN_libpthread
# define __libc_lock_trylock(NAME) \
# ifndef __libc_lock_trylock
# define __libc_lock_trylock(NAME) \
lll_trylock (NAME)
# endif
#else
# undef __libc_lock_trylock
# define __libc_lock_trylock(NAME) \
__libc_maybe_call (__pthread_mutex_trylock, (&(NAME)), 0)
#endif

6
ports/ChangeLog.mips
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@ -1,3 +1,9 @@
2012-08-15 Tom de Vries <vries@codesourcery.com>
Maxim Kuvyrkov <maxim@codesourcery.com>
* sysdeps/unix/sysv/linux/mips/nptl/lowlevellock.h (__libc_lock_lock)
(__libc_lock_trylock): Define versions optimized for MIPS.
2012-08-15 Maxim Kuvyrkov <maxim@codesourcery.com>
* sysdeps/mips/nptl/pthread_spin_lock.S: Remove, use generic version.

39
ports/sysdeps/unix/sysv/linux/mips/nptl/lowlevellock.h
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@ -1,5 +1,4 @@
/* Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008,
2009 Free Software Foundation, Inc.
/* Copyright (C) 2003-2012 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
@ -291,4 +290,40 @@ extern int __lll_timedwait_tid (int *, const struct timespec *)
__res; \
})
/* Implement __libc_lock_lock using exchange_and_add, which expands into
a single instruction on XLP processors. We enable this for all MIPS
processors as atomic_exchange_and_add_acq and
atomic_compare_and_exchange_acq take the same time to execute.
This is a simplified expansion of ({ lll_lock (NAME, LLL_PRIVATE); 0; }).
Note: __lll_lock_wait_private() resets lock value to '2', which prevents
unbounded increase of the lock value and [with billions of threads]
overflow. */
#define __libc_lock_lock(NAME) \
({ \
int *__futex = &(NAME); \
if (__builtin_expect (atomic_exchange_and_add_acq (__futex, 1), 0)) \
__lll_lock_wait_private (__futex); \
0; \
})
#ifdef _MIPS_ARCH_XLP
/* The generic version using a single atomic_compare_and_exchange_acq takes
less time for non-XLP processors, so we use below for XLP only. */
# define __libc_lock_trylock(NAME) \
({ \
int *__futex = &(NAME); \
int __result = atomic_exchange_and_add_acq (__futex, 1); \
/* If __result == 0, we succeeded in acquiring the lock. \
If __result == 1, we switched the lock to 'contended' state, which \
will cause a [possibly unnecessary] call to lll_futex_wait. This is \
unlikely, so we accept the possible inefficiency. \
If __result >= 2, we need to set the lock to 'contended' state to avoid \
unbounded increase from subsequent trylocks. */ \
if (__result >= 2) \
__result = atomic_exchange_acq (__futex, 2); \
__result; \
})
#endif
#endif /* lowlevellock.h */