Commit-ID: 335d7afbfb71faac833734a94240c1e07cf0ead8 Gitweb: http://git.kernel.org/tip/335d7afbfb71faac833734a94240c1e07cf0ead8 Author: Gerald Schaefer <gerald.schaefer@xxxxxxxxxx> AuthorDate: Mon, 22 Nov 2010 15:47:36 +0100 Committer: Ingo Molnar <mingo@xxxxxxx> CommitDate: Fri, 26 Nov 2010 15:05:34 +0100 mutexes, sched: Introduce arch_mutex_cpu_relax() The spinning mutex implementation uses cpu_relax() in busy loops as a compiler barrier. Depending on the architecture, cpu_relax() may do more than needed in this specific mutex spin loops. On System z we also give up the time slice of the virtual cpu in cpu_relax(), which prevents effective spinning on the mutex. This patch replaces cpu_relax() in the spinning mutex code with arch_mutex_cpu_relax(), which can be defined by each architecture that selects HAVE_ARCH_MUTEX_CPU_RELAX. The default is still cpu_relax(), so this patch should not affect other architectures than System z for now. Signed-off-by: Gerald Schaefer <gerald.schaefer@xxxxxxxxxx> Signed-off-by: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx> LKML-Reference: <1290437256.7455.4.camel@thinkpad> Signed-off-by: Ingo Molnar <mingo@xxxxxxx> --- arch/Kconfig | 3 +++ arch/s390/Kconfig | 1 + arch/s390/include/asm/mutex.h | 2 ++ include/linux/mutex.h | 4 ++++ kernel/mutex.c | 2 +- kernel/sched.c | 3 ++- 6 files changed, 13 insertions(+), 2 deletions(-) diff --git a/arch/Kconfig b/arch/Kconfig index 8bf0fa65..f78c2be 100644 --- a/arch/Kconfig +++ b/arch/Kconfig @@ -175,4 +175,7 @@ config HAVE_PERF_EVENTS_NMI config HAVE_ARCH_JUMP_LABEL bool +config HAVE_ARCH_MUTEX_CPU_RELAX + bool + source "kernel/gcov/Kconfig" diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig index e0b98e7..6c6d7b3 100644 --- a/arch/s390/Kconfig +++ b/arch/s390/Kconfig @@ -99,6 +99,7 @@ config S390 select HAVE_KERNEL_LZMA select HAVE_KERNEL_LZO select HAVE_GET_USER_PAGES_FAST + select HAVE_ARCH_MUTEX_CPU_RELAX select ARCH_INLINE_SPIN_TRYLOCK select ARCH_INLINE_SPIN_TRYLOCK_BH select ARCH_INLINE_SPIN_LOCK diff --git a/arch/s390/include/asm/mutex.h b/arch/s390/include/asm/mutex.h index 458c1f7..688271f 100644 --- a/arch/s390/include/asm/mutex.h +++ b/arch/s390/include/asm/mutex.h @@ -7,3 +7,5 @@ */ #include <asm-generic/mutex-dec.h> + +#define arch_mutex_cpu_relax() barrier() diff --git a/include/linux/mutex.h b/include/linux/mutex.h index f363bc8..94b48bd 100644 --- a/include/linux/mutex.h +++ b/include/linux/mutex.h @@ -160,4 +160,8 @@ extern int mutex_trylock(struct mutex *lock); extern void mutex_unlock(struct mutex *lock); extern int atomic_dec_and_mutex_lock(atomic_t *cnt, struct mutex *lock); +#ifndef CONFIG_HAVE_ARCH_MUTEX_CPU_RELAX +#define arch_mutex_cpu_relax() cpu_relax() +#endif + #endif diff --git a/kernel/mutex.c b/kernel/mutex.c index 200407c..a5889fb 100644 --- a/kernel/mutex.c +++ b/kernel/mutex.c @@ -199,7 +199,7 @@ __mutex_lock_common(struct mutex *lock, long state, unsigned int subclass, * memory barriers as we'll eventually observe the right * values at the cost of a few extra spins. */ - cpu_relax(); + arch_mutex_cpu_relax(); } #endif spin_lock_mutex(&lock->wait_lock, flags); diff --git a/kernel/sched.c b/kernel/sched.c index 3e8a7db..abe7aec 100644 --- a/kernel/sched.c +++ b/kernel/sched.c @@ -75,6 +75,7 @@ #include <asm/tlb.h> #include <asm/irq_regs.h> +#include <asm/mutex.h> #include "sched_cpupri.h" #include "workqueue_sched.h" @@ -3888,7 +3889,7 @@ int mutex_spin_on_owner(struct mutex *lock, struct thread_info *owner) if (task_thread_info(rq->curr) != owner || need_resched()) return 0; - cpu_relax(); + arch_mutex_cpu_relax(); } return 1; -- To unsubscribe from this list: send the line "unsubscribe linux-tip-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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