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authorPaul E. McKenney <paul.mckenney@linaro.org>2012-03-27 16:02:08 -0700
committerPaul E. McKenney <paulmck@linux.vnet.ibm.com>2012-05-02 14:43:23 -0700
commit616c310e83b872024271c915c1b9ab505b9efad9 (patch)
tree1339bc7b3bef920b4641a5af2f182e9dfa2a6632 /kernel
parent66f75a5d028beaf67c931435fdc3e7823125730c (diff)
downloadlinux-616c310e83b872024271c915c1b9ab505b9efad9.tar.gz
rcu: Move PREEMPT_RCU preemption to switch_to() invocation
Currently, PREEMPT_RCU readers are enqueued upon entry to the scheduler. This is inefficient because enqueuing is required only if there is a context switch, and entry to the scheduler does not guarantee a context switch. The commit therefore moves the enqueuing to immediately precede the call to switch_to() from the scheduler. Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Tested-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/rcutree.c1
-rw-r--r--kernel/rcutree.h1
-rw-r--r--kernel/rcutree_plugin.h14
-rw-r--r--kernel/sched/core.c1
4 files changed, 4 insertions, 13 deletions
diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index 1050d6d3922..61351505ec7 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -192,7 +192,6 @@ void rcu_note_context_switch(int cpu)
{
trace_rcu_utilization("Start context switch");
rcu_sched_qs(cpu);
- rcu_preempt_note_context_switch(cpu);
trace_rcu_utilization("End context switch");
}
EXPORT_SYMBOL_GPL(rcu_note_context_switch);
diff --git a/kernel/rcutree.h b/kernel/rcutree.h
index cdd1be0a407..d6b70b08a01 100644
--- a/kernel/rcutree.h
+++ b/kernel/rcutree.h
@@ -423,7 +423,6 @@ DECLARE_PER_CPU(char, rcu_cpu_has_work);
/* Forward declarations for rcutree_plugin.h */
static void rcu_bootup_announce(void);
long rcu_batches_completed(void);
-static void rcu_preempt_note_context_switch(int cpu);
static int rcu_preempt_blocked_readers_cgp(struct rcu_node *rnp);
#ifdef CONFIG_HOTPLUG_CPU
static void rcu_report_unblock_qs_rnp(struct rcu_node *rnp,
diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h
index c023464816b..b1ac22e6fa3 100644
--- a/kernel/rcutree_plugin.h
+++ b/kernel/rcutree_plugin.h
@@ -153,7 +153,7 @@ static void rcu_preempt_qs(int cpu)
*
* Caller must disable preemption.
*/
-static void rcu_preempt_note_context_switch(int cpu)
+void rcu_preempt_note_context_switch(void)
{
struct task_struct *t = current;
unsigned long flags;
@@ -164,7 +164,7 @@ static void rcu_preempt_note_context_switch(int cpu)
(t->rcu_read_unlock_special & RCU_READ_UNLOCK_BLOCKED) == 0) {
/* Possibly blocking in an RCU read-side critical section. */
- rdp = per_cpu_ptr(rcu_preempt_state.rda, cpu);
+ rdp = __this_cpu_ptr(rcu_preempt_state.rda);
rnp = rdp->mynode;
raw_spin_lock_irqsave(&rnp->lock, flags);
t->rcu_read_unlock_special |= RCU_READ_UNLOCK_BLOCKED;
@@ -228,7 +228,7 @@ static void rcu_preempt_note_context_switch(int cpu)
* means that we continue to block the current grace period.
*/
local_irq_save(flags);
- rcu_preempt_qs(cpu);
+ rcu_preempt_qs(smp_processor_id());
local_irq_restore(flags);
}
@@ -1018,14 +1018,6 @@ void rcu_force_quiescent_state(void)
EXPORT_SYMBOL_GPL(rcu_force_quiescent_state);
/*
- * Because preemptible RCU does not exist, we never have to check for
- * CPUs being in quiescent states.
- */
-static void rcu_preempt_note_context_switch(int cpu)
-{
-}
-
-/*
* Because preemptible RCU does not exist, there are never any preempted
* RCU readers.
*/
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 4603b9d8f30..5d89eb93f7e 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -2083,6 +2083,7 @@ context_switch(struct rq *rq, struct task_struct *prev,
#endif
/* Here we just switch the register state and the stack. */
+ rcu_switch_from(prev);
switch_to(prev, next, prev);
barrier();