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| author | Maxim Kuvyrkov <maxim@codesourcery.com> | 2012-08-15 16:44:30 -0700 |
|---|---|---|
| committer | Maxim Kuvyrkov <maxim@codesourcery.com> | 2012-08-15 16:44:30 -0700 |
| commit | 309becf120640bb0fdd1a16e65996c23d0542590 (patch) | |
| tree | 6adbada4d391a306dd2e4558626f759a7cadbed7 /ports | |
| parent | ef4009734b84903615be28b38638c166e5455692 (diff) | |
| download | glibc-309becf120640bb0fdd1a16e65996c23d0542590.tar.gz glibc-309becf120640bb0fdd1a16e65996c23d0542590.tar.xz glibc-309becf120640bb0fdd1a16e65996c23d0542590.zip | |
Optimize __libc_lock_lock and __libc_lock_trylock for MIPS.
Diffstat (limited to 'ports')
| -rw-r--r-- | ports/ChangeLog.mips | 6 | ||||
| -rw-r--r-- | ports/sysdeps/unix/sysv/linux/mips/nptl/lowlevellock.h | 39 |
2 files changed, 43 insertions, 2 deletions
diff --git a/ports/ChangeLog.mips b/ports/ChangeLog.mips index 518777223c..f8c18b3275 100644 --- a/ports/ChangeLog.mips +++ b/ports/ChangeLog.mips @@ -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. diff --git a/ports/sysdeps/unix/sysv/linux/mips/nptl/lowlevellock.h b/ports/sysdeps/unix/sysv/linux/mips/nptl/lowlevellock.h index 88b601eadd..d368ae1b66 100644 --- a/ports/sysdeps/unix/sysv/linux/mips/nptl/lowlevellock.h +++ b/ports/sysdeps/unix/sysv/linux/mips/nptl/lowlevellock.h @@ -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 */ |