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authorPeter Zijlstra <a.p.zijlstra@chello.nl>2011-04-05 17:23:40 +0200
committerIngo Molnar <mingo@elte.hu>2011-04-14 08:52:32 +0200
commit3ca7a440da394808571dad32d33d3bc0389982e6 (patch)
treeed749666030d201249f62a8dcb93224271d43241
parent184748cc50b2dceb8287f9fb657eda48ff8fcfe7 (diff)
downloadlinaro-lsk-3ca7a440da394808571dad32d33d3bc0389982e6.tar.gz
sched: Always provide p->on_cpu
Always provide p->on_cpu so that we can determine if its on a cpu without having to lock the rq. Reviewed-by: Frank Rowand <frank.rowand@am.sony.com> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Mike Galbraith <efault@gmx.de> Cc: Nick Piggin <npiggin@kernel.dk> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andrew Morton <akpm@linux-foundation.org> Link: http://lkml.kernel.org/r/20110405152728.785452014@chello.nl Signed-off-by: Ingo Molnar <mingo@elte.hu>
-rw-r--r--include/linux/sched.h4
-rw-r--r--kernel/sched.c46
2 files changed, 30 insertions, 20 deletions
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 758e27afcda..3435837e89f 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1200,9 +1200,7 @@ struct task_struct {
int lock_depth; /* BKL lock depth */
#ifdef CONFIG_SMP
-#ifdef __ARCH_WANT_UNLOCKED_CTXSW
- int oncpu;
-#endif
+ int on_cpu;
#endif
int prio, static_prio, normal_prio;
diff --git a/kernel/sched.c b/kernel/sched.c
index a187c3fe027..cd2593e1a3e 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -838,18 +838,39 @@ static inline int task_current(struct rq *rq, struct task_struct *p)
return rq->curr == p;
}
-#ifndef __ARCH_WANT_UNLOCKED_CTXSW
static inline int task_running(struct rq *rq, struct task_struct *p)
{
+#ifdef CONFIG_SMP
+ return p->on_cpu;
+#else
return task_current(rq, p);
+#endif
}
+#ifndef __ARCH_WANT_UNLOCKED_CTXSW
static inline void prepare_lock_switch(struct rq *rq, struct task_struct *next)
{
+#ifdef CONFIG_SMP
+ /*
+ * We can optimise this out completely for !SMP, because the
+ * SMP rebalancing from interrupt is the only thing that cares
+ * here.
+ */
+ next->on_cpu = 1;
+#endif
}
static inline void finish_lock_switch(struct rq *rq, struct task_struct *prev)
{
+#ifdef CONFIG_SMP
+ /*
+ * After ->on_cpu is cleared, the task can be moved to a different CPU.
+ * We must ensure this doesn't happen until the switch is completely
+ * finished.
+ */
+ smp_wmb();
+ prev->on_cpu = 0;
+#endif
#ifdef CONFIG_DEBUG_SPINLOCK
/* this is a valid case when another task releases the spinlock */
rq->lock.owner = current;
@@ -865,15 +886,6 @@ static inline void finish_lock_switch(struct rq *rq, struct task_struct *prev)
}
#else /* __ARCH_WANT_UNLOCKED_CTXSW */
-static inline int task_running(struct rq *rq, struct task_struct *p)
-{
-#ifdef CONFIG_SMP
- return p->oncpu;
-#else
- return task_current(rq, p);
-#endif
-}
-
static inline void prepare_lock_switch(struct rq *rq, struct task_struct *next)
{
#ifdef CONFIG_SMP
@@ -882,7 +894,7 @@ static inline void prepare_lock_switch(struct rq *rq, struct task_struct *next)
* SMP rebalancing from interrupt is the only thing that cares
* here.
*/
- next->oncpu = 1;
+ next->on_cpu = 1;
#endif
#ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW
raw_spin_unlock_irq(&rq->lock);
@@ -895,12 +907,12 @@ static inline void finish_lock_switch(struct rq *rq, struct task_struct *prev)
{
#ifdef CONFIG_SMP
/*
- * After ->oncpu is cleared, the task can be moved to a different CPU.
+ * After ->on_cpu is cleared, the task can be moved to a different CPU.
* We must ensure this doesn't happen until the switch is completely
* finished.
*/
smp_wmb();
- prev->oncpu = 0;
+ prev->on_cpu = 0;
#endif
#ifndef __ARCH_WANT_INTERRUPTS_ON_CTXSW
local_irq_enable();
@@ -2686,8 +2698,8 @@ void sched_fork(struct task_struct *p, int clone_flags)
if (likely(sched_info_on()))
memset(&p->sched_info, 0, sizeof(p->sched_info));
#endif
-#if defined(CONFIG_SMP) && defined(__ARCH_WANT_UNLOCKED_CTXSW)
- p->oncpu = 0;
+#if defined(CONFIG_SMP)
+ p->on_cpu = 0;
#endif
#ifdef CONFIG_PREEMPT
/* Want to start with kernel preemption disabled. */
@@ -5776,8 +5788,8 @@ void __cpuinit init_idle(struct task_struct *idle, int cpu)
rcu_read_unlock();
rq->curr = rq->idle = idle;
-#if defined(CONFIG_SMP) && defined(__ARCH_WANT_UNLOCKED_CTXSW)
- idle->oncpu = 1;
+#if defined(CONFIG_SMP)
+ idle->on_cpu = 1;
#endif
raw_spin_unlock_irqrestore(&rq->lock, flags);