From: Heiko Carstens <heiko.carst...@de.ibm.com> 3.12-stable review patch. If anyone has any objections, please let me know.
=============== commit 03b8c7b623c80af264c4c8d6111e5c6289933666 upstream. If an architecture has futex_atomic_cmpxchg_inatomic() implemented and there is no runtime check necessary, allow to skip the test within futex_init(). This allows to get rid of some code which would always give the same result, and also allows the compiler to optimize a couple of if statements away. Signed-off-by: Heiko Carstens <heiko.carst...@de.ibm.com> Cc: Finn Thain <fth...@telegraphics.com.au> Cc: Geert Uytterhoeven <ge...@linux-m68k.org> Link: http://lkml.kernel.org/r/20140302120947.GA3641@osiris Signed-off-by: Thomas Gleixner <t...@linutronix.de> [geert: Backported to v3.10..v3.13] Signed-off-by: Geert Uytterhoeven <ge...@linux-m68k.org> Signed-off-by: Jiri Slaby <jsl...@suse.cz> --- arch/s390/Kconfig | 1 + include/linux/futex.h | 4 ++++ init/Kconfig | 7 +++++++ kernel/futex.c | 14 ++++++++++++-- 4 files changed, 24 insertions(+), 2 deletions(-) diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig index 3e01afa21710..6671e8db1861 100644 --- a/arch/s390/Kconfig +++ b/arch/s390/Kconfig @@ -116,6 +116,7 @@ config S390 select HAVE_FUNCTION_GRAPH_TRACER select HAVE_FUNCTION_TRACER select HAVE_FUNCTION_TRACE_MCOUNT_TEST + select HAVE_FUTEX_CMPXCHG if FUTEX select HAVE_KERNEL_BZIP2 select HAVE_KERNEL_GZIP select HAVE_KERNEL_LZ4 diff --git a/include/linux/futex.h b/include/linux/futex.h index b0d95cac826e..6435f46d6e13 100644 --- a/include/linux/futex.h +++ b/include/linux/futex.h @@ -55,7 +55,11 @@ union futex_key { #ifdef CONFIG_FUTEX extern void exit_robust_list(struct task_struct *curr); extern void exit_pi_state_list(struct task_struct *curr); +#ifdef CONFIG_HAVE_FUTEX_CMPXCHG +#define futex_cmpxchg_enabled 1 +#else extern int futex_cmpxchg_enabled; +#endif #else static inline void exit_robust_list(struct task_struct *curr) { diff --git a/init/Kconfig b/init/Kconfig index 3ecd8a1178f1..d42dc7c6ba64 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -1406,6 +1406,13 @@ config FUTEX support for "fast userspace mutexes". The resulting kernel may not run glibc-based applications correctly. +config HAVE_FUTEX_CMPXCHG + bool + help + Architectures should select this if futex_atomic_cmpxchg_inatomic() + is implemented and always working. This removes a couple of runtime + checks. + config EPOLL bool "Enable eventpoll support" if EXPERT default y diff --git a/kernel/futex.c b/kernel/futex.c index 231754863a87..d8347b7a064f 100644 --- a/kernel/futex.c +++ b/kernel/futex.c @@ -68,7 +68,9 @@ #include "rtmutex_common.h" +#ifndef CONFIG_HAVE_FUTEX_CMPXCHG int __read_mostly futex_cmpxchg_enabled; +#endif #define FUTEX_HASHBITS (CONFIG_BASE_SMALL ? 4 : 8) @@ -2731,10 +2733,10 @@ SYSCALL_DEFINE6(futex, u32 __user *, uaddr, int, op, u32, val, return do_futex(uaddr, op, val, tp, uaddr2, val2, val3); } -static int __init futex_init(void) +static void __init futex_detect_cmpxchg(void) { +#ifndef CONFIG_HAVE_FUTEX_CMPXCHG u32 curval; - int i; /* * This will fail and we want it. Some arch implementations do @@ -2748,6 +2750,14 @@ static int __init futex_init(void) */ if (cmpxchg_futex_value_locked(&curval, NULL, 0, 0) == -EFAULT) futex_cmpxchg_enabled = 1; +#endif +} + +static int __init futex_init(void) +{ + int i; + + futex_detect_cmpxchg(); for (i = 0; i < ARRAY_SIZE(futex_queues); i++) { plist_head_init(&futex_queues[i].chain); -- 1.9.2 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
