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Date: Thu, 21 Oct 2010 11:29:05 +0800
From: Lai Jiangshan <laijs@...fujitsu.com>
To: paulmck@...ux.vnet.ibm.com
CC: Ingo Molnar <mingo@...e.hu>, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2 v2] rcu,cleanup: move synchronize_sched_expedited()
out of sched.c
On 10/21/2010 08:19 AM, Paul E. McKenney wrote:
> On Wed, Oct 20, 2010 at 12:15:12PM -0700, Paul E. McKenney wrote:
>> On Wed, Oct 20, 2010 at 02:12:58PM +0800, Lai Jiangshan wrote:
>>> The first version of synchronize_sched_expedited() use the migration code
>>> of the scheduler code, so it have to be implemented in sched.c
>>>
>>> but now, the synchronize_sched_expedited() does not use such code,
>>> it is time to move it out of sched.c.
>>>
>>> Different rcu implementation' synchronize_sched_expedited() are also
>>> different. so we move synchronize_sched_expedited() to kernel/rcutree_plugin.h
>>> or include/linux/rcutiny.h instead of kerenl/rcupdate.c
>>
>> Queued, thank you!!!
>
> Hello again, Lai,
>
> I hit the following build error during testing:
>
> kernel/built-in.o: In function `.synchronize_rcu_expedited':
> (.text+0x787d8): undefined reference to `.synchronize_sched_expedited'
> kernel/built-in.o:(.toc1+0x1fe0): undefined reference to `synchronize_sched_expedited'
>
> This build uses defconfig with the following applied:
>
> CONFIG_RCU_TRACE=y
> CONFIG_RCU_FAST_NO_HZ=y
> CONFIG_NO_HZ=y
> CONFIG_RCU_CPU_STALL_DETECTOR=y
> CONFIG_SMP=y
> CONFIG_RCU_FANOUT=8
> CONFIG_NR_CPUS=8
> CONFIG_RCU_FANOUT_EXACT=n
> CONFIG_HOTPLUG_CPU=y
> CONFIG_PREEMPT_NONE=y
> CONFIG_PREEMPT_VOLUNTARY=n
> CONFIG_PREEMPT=n
> CONFIG_TREE_RCU=y
> CONFIG_TREE_PREEMPT_RCU=n
> CONFIG_RCU_TORTURE_TEST=m
> CONFIG_MODULE_UNLOAD=y
> CONFIG_SYSFS_DEPRECATED_V2=y
> CONFIG_IKCONFIG=y
> CONFIG_IKCONFIG_PROC=y
>
> Thoughts?
>
> Thanx, Paul
>
>
I moved the code into CONFIG_TREE_PREEMPT_RCU=y codes. fixed version:
Signed-off-by: Lai Jiangshan <laijs@...fujitsu.com>
---
diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index 0d0b640..ead36da 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 13877cb..4d84452 100644
--- a/include/linux/rcutiny.h
+++ b/include/linux/rcutiny.h
@@ -58,6 +58,11 @@ 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 95518e6..9a1fd6c 100644
--- a/include/linux/rcutree.h
+++ b/include/linux/rcutree.h
@@ -47,6 +47,7 @@ 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 0e75d60..0de359b 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 abf8440..9dc7775 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -9332,72 +9332,3 @@ 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 */
--
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