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authorGerald Schaefer <gerald.schaefer@de.ibm.com>2010-11-22 09:47:36 -0500
committerIngo Molnar <mingo@elte.hu>2010-11-26 09:05:34 -0500
commit335d7afbfb71faac833734a94240c1e07cf0ead8 (patch)
tree483a24c6005af6eb25a256d92a697411d94a7458 /kernel/sched.c
parent22a867d81707b0a2720bb5f65255265b95d30526 (diff)
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@de.ibm.com> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> LKML-Reference: <1290437256.7455.4.camel@thinkpad> Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'kernel/sched.c')
-rw-r--r--kernel/sched.c3
1 files changed, 2 insertions, 1 deletions
diff --git a/kernel/sched.c b/kernel/sched.c
index 3e8a7db951a6..abe7aec55763 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -75,6 +75,7 @@
75 75
76#include <asm/tlb.h> 76#include <asm/tlb.h>
77#include <asm/irq_regs.h> 77#include <asm/irq_regs.h>
78#include <asm/mutex.h>
78 79
79#include "sched_cpupri.h" 80#include "sched_cpupri.h"
80#include "workqueue_sched.h" 81#include "workqueue_sched.h"
@@ -3888,7 +3889,7 @@ int mutex_spin_on_owner(struct mutex *lock, struct thread_info *owner)
3888 if (task_thread_info(rq->curr) != owner || need_resched()) 3889 if (task_thread_info(rq->curr) != owner || need_resched())
3889 return 0; 3890 return 0;
3890 3891
3891 cpu_relax(); 3892 arch_mutex_cpu_relax();
3892 } 3893 }
3893 3894
3894 return 1; 3895 return 1;