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Date: Sat, 6 Nov 2010 19:05:28 -0700
From: "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To: linux-kernel@...r.kernel.org
Cc: mingo@...e.hu, laijs@...fujitsu.com, dipankar@...ibm.com,
akpm@...ux-foundation.org, mathieu.desnoyers@...ymtl.ca,
josh@...htriplett.org, niv@...ibm.com, tglx@...utronix.de,
peterz@...radead.org, rostedt@...dmis.org, Valdis.Kletnieks@...edu,
dhowells@...hat.com, eric.dumazet@...il.com, darren@...art.com,
"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Subject: [PATCH RFC tip/core/rcu 08/12] rcu,cleanup: move synchronize_sched_expedited() out of sched.c
From: Lai Jiangshan <laijs@...fujitsu.com>
The first version of synchronize_sched_expedited() used the migration
code in the scheduler, and was therefore implemented in kernel/sched.c.
However, the more recent version of this code no longer uses the
migration code, so this commit moves it to the main RCU source files.
Signed-off-by: Lai Jiangshan <laijs@...fujitsu.com>
Signed-off-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
---
include/linux/rcupdate.h | 1 -
include/linux/rcutiny.h | 5 +++
include/linux/rcutree.h | 1 +
kernel/rcutree_plugin.h | 71 ++++++++++++++++++++++++++++++++++++++++++++++
kernel/sched.c | 69 --------------------------------------------
5 files changed, 77 insertions(+), 70 deletions(-)
diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index 7142ee3..49e8e16 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -66,7 +66,6 @@ extern void call_rcu_sched(struct rcu_head *head,
extern void synchronize_sched(void);
extern void rcu_barrier_bh(void);
extern void rcu_barrier_sched(void);
-extern void synchronize_sched_expedited(void);
extern int sched_expedited_torture_stats(char *page);
static inline void __rcu_read_lock_bh(void)
diff --git a/include/linux/rcutiny.h b/include/linux/rcutiny.h
index ea025a6..30ebd7c 100644
--- a/include/linux/rcutiny.h
+++ b/include/linux/rcutiny.h
@@ -60,6 +60,11 @@ static inline void synchronize_rcu_bh_expedited(void)
synchronize_sched();
}
+static inline void synchronize_sched_expedited(void)
+{
+ synchronize_sched();
+}
+
#ifdef CONFIG_TINY_RCU
static inline void rcu_preempt_note_context_switch(void)
diff --git a/include/linux/rcutree.h b/include/linux/rcutree.h
index c0e9683..3a93348 100644
--- a/include/linux/rcutree.h
+++ b/include/linux/rcutree.h
@@ -48,6 +48,7 @@ static inline void exit_rcu(void)
#endif /* #else #ifdef CONFIG_TREE_PREEMPT_RCU */
extern void synchronize_rcu_bh(void);
+extern void synchronize_sched_expedited(void);
extern void synchronize_rcu_expedited(void);
static inline void synchronize_rcu_bh_expedited(void)
diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h
index 71a4147..21df7f3 100644
--- a/kernel/rcutree_plugin.h
+++ b/kernel/rcutree_plugin.h
@@ -25,6 +25,7 @@
*/
#include <linux/delay.h>
+#include <linux/stop_machine.h>
/*
* Check the RCU kernel configuration parameters and print informative
@@ -1014,6 +1015,76 @@ static void __init __rcu_init_preempt(void)
#endif /* #else #ifdef CONFIG_TREE_PREEMPT_RCU */
+#ifndef CONFIG_SMP
+
+void synchronize_sched_expedited(void)
+{
+ cond_resched();
+}
+EXPORT_SYMBOL_GPL(synchronize_sched_expedited);
+
+#else /* #ifndef CONFIG_SMP */
+
+static atomic_t synchronize_sched_expedited_count = ATOMIC_INIT(0);
+
+static int synchronize_sched_expedited_cpu_stop(void *data)
+{
+ /*
+ * There must be a full memory barrier on each affected CPU
+ * between the time that try_stop_cpus() is called and the
+ * time that it returns.
+ *
+ * In the current initial implementation of cpu_stop, the
+ * above condition is already met when the control reaches
+ * this point and the following smp_mb() is not strictly
+ * necessary. Do smp_mb() anyway for documentation and
+ * robustness against future implementation changes.
+ */
+ smp_mb(); /* See above comment block. */
+ return 0;
+}
+
+/*
+ * Wait for an rcu-sched grace period to elapse, but use "big hammer"
+ * approach to force grace period to end quickly. This consumes
+ * significant time on all CPUs, and is thus not recommended for
+ * any sort of common-case code.
+ *
+ * Note that it is illegal to call this function while holding any
+ * lock that is acquired by a CPU-hotplug notifier. Failing to
+ * observe this restriction will result in deadlock.
+ */
+void synchronize_sched_expedited(void)
+{
+ int snap, trycount = 0;
+
+ smp_mb(); /* ensure prior mod happens before capturing snap. */
+ snap = atomic_read(&synchronize_sched_expedited_count) + 1;
+ get_online_cpus();
+ while (try_stop_cpus(cpu_online_mask,
+ synchronize_sched_expedited_cpu_stop,
+ NULL) == -EAGAIN) {
+ put_online_cpus();
+ if (trycount++ < 10)
+ udelay(trycount * num_online_cpus());
+ else {
+ synchronize_sched();
+ return;
+ }
+ if (atomic_read(&synchronize_sched_expedited_count) - snap > 0) {
+ smp_mb(); /* ensure test happens before caller kfree */
+ return;
+ }
+ get_online_cpus();
+ }
+ atomic_inc(&synchronize_sched_expedited_count);
+ smp_mb__after_atomic_inc(); /* ensure post-GP actions seen after GP. */
+ put_online_cpus();
+}
+EXPORT_SYMBOL_GPL(synchronize_sched_expedited);
+
+#endif /* #else #ifndef CONFIG_SMP */
+
#if !defined(CONFIG_RCU_FAST_NO_HZ)
/*
diff --git a/kernel/sched.c b/kernel/sched.c
index ae8f75a..d1e8889 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -9131,72 +9131,3 @@ struct cgroup_subsys cpuacct_subsys = {
};
#endif /* CONFIG_CGROUP_CPUACCT */
-#ifndef CONFIG_SMP
-
-void synchronize_sched_expedited(void)
-{
- barrier();
-}
-EXPORT_SYMBOL_GPL(synchronize_sched_expedited);
-
-#else /* #ifndef CONFIG_SMP */
-
-static atomic_t synchronize_sched_expedited_count = ATOMIC_INIT(0);
-
-static int synchronize_sched_expedited_cpu_stop(void *data)
-{
- /*
- * There must be a full memory barrier on each affected CPU
- * between the time that try_stop_cpus() is called and the
- * time that it returns.
- *
- * In the current initial implementation of cpu_stop, the
- * above condition is already met when the control reaches
- * this point and the following smp_mb() is not strictly
- * necessary. Do smp_mb() anyway for documentation and
- * robustness against future implementation changes.
- */
- smp_mb(); /* See above comment block. */
- return 0;
-}
-
-/*
- * Wait for an rcu-sched grace period to elapse, but use "big hammer"
- * approach to force grace period to end quickly. This consumes
- * significant time on all CPUs, and is thus not recommended for
- * any sort of common-case code.
- *
- * Note that it is illegal to call this function while holding any
- * lock that is acquired by a CPU-hotplug notifier. Failing to
- * observe this restriction will result in deadlock.
- */
-void synchronize_sched_expedited(void)
-{
- int snap, trycount = 0;
-
- smp_mb(); /* ensure prior mod happens before capturing snap. */
- snap = atomic_read(&synchronize_sched_expedited_count) + 1;
- get_online_cpus();
- while (try_stop_cpus(cpu_online_mask,
- synchronize_sched_expedited_cpu_stop,
- NULL) == -EAGAIN) {
- put_online_cpus();
- if (trycount++ < 10)
- udelay(trycount * num_online_cpus());
- else {
- synchronize_sched();
- return;
- }
- if (atomic_read(&synchronize_sched_expedited_count) - snap > 0) {
- smp_mb(); /* ensure test happens before caller kfree */
- return;
- }
- get_online_cpus();
- }
- atomic_inc(&synchronize_sched_expedited_count);
- smp_mb__after_atomic_inc(); /* ensure post-GP actions seen after GP. */
- put_online_cpus();
-}
-EXPORT_SYMBOL_GPL(synchronize_sched_expedited);
-
-#endif /* #else #ifndef CONFIG_SMP */
--
1.7.0.6
--
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