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authorPaul E. McKenney <paulmck@linux.vnet.ibm.com>2015-02-18 12:24:30 -0800
committerPaul E. McKenney <paulmck@linux.vnet.ibm.com>2015-02-26 12:02:59 -0800
commit0d39482c3db13aae1db143d340816108dd53e443 (patch)
treedbcf5c785244bd29da2190d65a92fb1ca497a009 /kernel/rcu/update.c
parentc517d838eb7d07bbe9507871fab3931deccff539 (diff)
downloadlinux-sh-0d39482c3db13aae1db143d340816108dd53e443.tar.gz
rcu: Provide rcu_expedite_gp() and rcu_unexpedite_gp()
Currently, expediting of normal synchronous grace-period primitives (synchronize_rcu() and friends) is controlled by the rcu_expedited() boot/sysfs parameter. This works well, but does not handle nesting. This commit therefore provides rcu_expedite_gp() to enable expediting and rcu_unexpedite_gp() to cancel a prior rcu_expedite_gp(), both of which support nesting. Reported-by: Arjan van de Ven <arjan@linux.intel.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Diffstat (limited to 'kernel/rcu/update.c')
-rw-r--r--kernel/rcu/update.c48
1 files changed, 48 insertions, 0 deletions
diff --git a/kernel/rcu/update.c b/kernel/rcu/update.c
index e0d31a345ee6..5f850823c187 100644
--- a/kernel/rcu/update.c
+++ b/kernel/rcu/update.c
@@ -62,6 +62,54 @@ MODULE_ALIAS("rcupdate");
module_param(rcu_expedited, int, 0);
+#ifndef CONFIG_TINY_RCU
+
+static atomic_t rcu_expedited_nesting;
+
+/*
+ * Should normal grace-period primitives be expedited? Intended for
+ * use within RCU. Note that this function takes the rcu_expedited
+ * sysfs/boot variable into account as well as the rcu_expedite_gp()
+ * nesting. So looping on rcu_unexpedite_gp() until rcu_gp_is_expedited()
+ * returns false is a -really- bad idea.
+ */
+bool rcu_gp_is_expedited(void)
+{
+ return rcu_expedited || atomic_read(&rcu_expedited_nesting);
+}
+EXPORT_SYMBOL_GPL(rcu_gp_is_expedited);
+
+/**
+ * rcu_expedite_gp - Expedite future RCU grace periods
+ *
+ * After a call to this function, future calls to synchronize_rcu() and
+ * friends act as the corresponding synchronize_rcu_expedited() function
+ * had instead been called.
+ */
+void rcu_expedite_gp(void)
+{
+ atomic_inc(&rcu_expedited_nesting);
+}
+EXPORT_SYMBOL_GPL(rcu_expedite_gp);
+
+/**
+ * rcu_unexpedite_gp - Cancel prior rcu_expedite_gp() invocation
+ *
+ * Undo a prior call to rcu_expedite_gp(). If all prior calls to
+ * rcu_expedite_gp() are undone by a subsequent call to rcu_unexpedite_gp(),
+ * and if the rcu_expedited sysfs/boot parameter is not set, then all
+ * subsequent calls to synchronize_rcu() and friends will return to
+ * their normal non-expedited behavior.
+ */
+void rcu_unexpedite_gp(void)
+{
+ atomic_dec(&rcu_expedited_nesting);
+}
+EXPORT_SYMBOL_GPL(rcu_unexpedite_gp);
+
+#endif /* #ifndef CONFIG_TINY_RCU */
+
+
#ifdef CONFIG_PREEMPT_RCU
/*