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authorPaul E. McKenney <paulmck@linux.vnet.ibm.com>2010-02-25 14:06:47 -0800
committerIngo Molnar <mingo@elte.hu>2010-02-26 08:20:46 +0100
commitd9f1bb6ad7fc53c406706f47858dd5ff030b14a3 (patch)
tree4af519d68b396e372e6a5afbb5e968de3bacd123 /kernel/rcupdate.c
parent056ba4a9bea5f32781a36b797c562fb731e5eaa6 (diff)
downloadlinux-linaro-stable-d9f1bb6ad7fc53c406706f47858dd5ff030b14a3.tar.gz
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@linux.vnet.ibm.com> Cc: laijs@cn.fujitsu.com Cc: dipankar@in.ibm.com Cc: mathieu.desnoyers@polymtl.ca Cc: josh@joshtriplett.org Cc: dvhltc@us.ibm.com Cc: niv@us.ibm.com Cc: peterz@infradead.org Cc: rostedt@goodmis.org Cc: Valdis.Kletnieks@vt.edu Cc: dhowells@redhat.com LKML-Reference: <1267135607-7056-2-git-send-email-paulmck@linux.vnet.ibm.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'kernel/rcupdate.c')
-rw-r--r--kernel/rcupdate.c18
1 files changed, 18 insertions, 0 deletions
diff --git a/kernel/rcupdate.c b/kernel/rcupdate.c
index 033cb55c26df..7bfa004572b1 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.