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Message-Id: <1267135607-7056-2-git-send-email-paulmck@linux.vnet.ibm.com>
Date: Thu, 25 Feb 2010 14:06:47 -0800
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, dvhltc@...ibm.com, niv@...ibm.com,
tglx@...utronix.de, peterz@...radead.org, rostedt@...dmis.org,
Valdis.Kletnieks@...edu, dhowells@...hat.com,
"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Subject: [PATCH tip/core/rcu 2/2] rcu: make rcu_read_lock_sched_held() take boot time into account
Before the scheduler starts, all tasks are non-preemptible by definition.
So, during that time, rcu_read_lock_sched_held() needs to always return
"true". This patch makes that be so.
Signed-off-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
---
include/linux/rcupdate.h | 4 +++-
include/linux/rcutiny.h | 4 ----
include/linux/rcutree.h | 1 -
kernel/rcupdate.c | 18 ++++++++++++++++++
kernel/rcutree.c | 19 -------------------
5 files changed, 21 insertions(+), 25 deletions(-)
diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index 1a4de31..fcea332 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -62,6 +62,8 @@ extern int sched_expedited_torture_stats(char *page);
/* Internal to kernel */
extern void rcu_init(void);
+extern int rcu_scheduler_active;
+extern void rcu_scheduler_starting(void);
#if defined(CONFIG_TREE_RCU) || defined(CONFIG_TREE_PREEMPT_RCU)
#include <linux/rcutree.h>
@@ -140,7 +142,7 @@ static inline int rcu_read_lock_sched_held(void)
if (debug_locks)
lockdep_opinion = lock_is_held(&rcu_sched_lock_map);
- return lockdep_opinion || preempt_count() != 0;
+ return lockdep_opinion || preempt_count() != 0 || !rcu_scheduler_active;
}
#else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
diff --git a/include/linux/rcutiny.h b/include/linux/rcutiny.h
index 2b70d4e..a519587 100644
--- a/include/linux/rcutiny.h
+++ b/include/linux/rcutiny.h
@@ -105,10 +105,6 @@ static inline void rcu_exit_nohz(void)
#endif /* #else #ifdef CONFIG_NO_HZ */
-static inline void rcu_scheduler_starting(void)
-{
-}
-
static inline void exit_rcu(void)
{
}
diff --git a/include/linux/rcutree.h b/include/linux/rcutree.h
index 704a010..42cc3a0 100644
--- a/include/linux/rcutree.h
+++ b/include/linux/rcutree.h
@@ -35,7 +35,6 @@ struct notifier_block;
extern void rcu_sched_qs(int cpu);
extern void rcu_bh_qs(int cpu);
extern int rcu_needs_cpu(int cpu);
-extern void rcu_scheduler_starting(void);
extern int rcu_expedited_torture_stats(char *page);
#ifdef CONFIG_TREE_PREEMPT_RCU
diff --git a/kernel/rcupdate.c b/kernel/rcupdate.c
index 033cb55..7bfa004 100644
--- a/kernel/rcupdate.c
+++ b/kernel/rcupdate.c
@@ -44,6 +44,7 @@
#include <linux/cpu.h>
#include <linux/mutex.h>
#include <linux/module.h>
+#include <linux/kernel_stat.h>
#ifdef CONFIG_DEBUG_LOCK_ALLOC
static struct lock_class_key rcu_lock_key;
@@ -62,6 +63,23 @@ struct lockdep_map rcu_sched_lock_map =
EXPORT_SYMBOL_GPL(rcu_sched_lock_map);
#endif
+int rcu_scheduler_active __read_mostly;
+
+/*
+ * This function is invoked towards the end of the scheduler's initialization
+ * process. Before this is called, the idle task might contain
+ * RCU read-side critical sections (during which time, this idle
+ * task is booting the system). After this function is called, the
+ * idle tasks are prohibited from containing RCU read-side critical
+ * sections.
+ */
+void rcu_scheduler_starting(void)
+{
+ WARN_ON(num_online_cpus() != 1);
+ WARN_ON(nr_context_switches() > 0);
+ rcu_scheduler_active = 1;
+}
+
/*
* Awaken the corresponding synchronize_rcu() instance now that a
* grace period has elapsed.
diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index 525d398..335bfe4 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -46,7 +46,6 @@
#include <linux/cpu.h>
#include <linux/mutex.h>
#include <linux/time.h>
-#include <linux/kernel_stat.h>
#include "rcutree.h"
@@ -81,9 +80,6 @@ DEFINE_PER_CPU(struct rcu_data, rcu_sched_data);
struct rcu_state rcu_bh_state = RCU_STATE_INITIALIZER(rcu_bh_state);
DEFINE_PER_CPU(struct rcu_data, rcu_bh_data);
-static int rcu_scheduler_active __read_mostly;
-
-
/*
* Return true if an RCU grace period is in progress. The ACCESS_ONCE()s
* permit this function to be invoked without holding the root rcu_node
@@ -1565,21 +1561,6 @@ static int rcu_needs_cpu_quick_check(int cpu)
rcu_preempt_needs_cpu(cpu);
}
-/*
- * This function is invoked towards the end of the scheduler's initialization
- * process. Before this is called, the idle task might contain
- * RCU read-side critical sections (during which time, this idle
- * task is booting the system). After this function is called, the
- * idle tasks are prohibited from containing RCU read-side critical
- * sections.
- */
-void rcu_scheduler_starting(void)
-{
- WARN_ON(num_online_cpus() != 1);
- WARN_ON(nr_context_switches() > 0);
- rcu_scheduler_active = 1;
-}
-
static DEFINE_PER_CPU(struct rcu_head, rcu_barrier_head) = {NULL};
static atomic_t rcu_barrier_cpu_count;
static DEFINE_MUTEX(rcu_barrier_mutex);
--
1.6.6
--
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