summaryrefslogtreecommitdiff
path: root/kernel/rcu/tree.c
diff options
context:
space:
mode:
authorPaul E. McKenney <paulmck@linux.vnet.ibm.com>2015-07-31 13:34:32 -0700
committerPaul E. McKenney <paulmck@linux.vnet.ibm.com>2015-09-20 21:16:18 -0700
commit7922cd0e562cb2b8da2c8a0afda2e1c9bb4a94e2 (patch)
treedce739485e55be9238c53bf70530a0b5e5a34aa3 /kernel/rcu/tree.c
parentf4ecea309d3e17ba5e90082308125ad23bd5701b (diff)
downloadlinux-sh-7922cd0e562cb2b8da2c8a0afda2e1c9bb4a94e2.tar.gz
rcu: Move rcu_report_exp_rnp() to allow consolidation
This is a nearly pure code-movement commit, moving rcu_report_exp_rnp(), sync_rcu_preempt_exp_done(), and rcu_preempted_readers_exp() so that later commits can make synchronize_sched_expedited() use them. The non-code-movement portion of this commit tags rcu_report_exp_rnp() as __maybe_unused to avoid build errors when CONFIG_PREEMPT=n. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Diffstat (limited to 'kernel/rcu/tree.c')
-rw-r--r--kernel/rcu/tree.c66
1 files changed, 66 insertions, 0 deletions
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 53d66ebb4811..59af27d8bc6a 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -3379,6 +3379,72 @@ static bool rcu_exp_gp_seq_done(struct rcu_state *rsp, unsigned long s)
return rcu_seq_done(&rsp->expedited_sequence, s);
}
+/*
+ * Return non-zero if there are any tasks in RCU read-side critical
+ * sections blocking the current preemptible-RCU expedited grace period.
+ * If there is no preemptible-RCU expedited grace period currently in
+ * progress, returns zero unconditionally.
+ */
+static int rcu_preempted_readers_exp(struct rcu_node *rnp)
+{
+ return rnp->exp_tasks != NULL;
+}
+
+/*
+ * return non-zero if there is no RCU expedited grace period in progress
+ * for the specified rcu_node structure, in other words, if all CPUs and
+ * tasks covered by the specified rcu_node structure have done their bit
+ * for the current expedited grace period. Works only for preemptible
+ * RCU -- other RCU implementation use other means.
+ *
+ * Caller must hold the root rcu_node's exp_funnel_mutex.
+ */
+static int sync_rcu_preempt_exp_done(struct rcu_node *rnp)
+{
+ return !rcu_preempted_readers_exp(rnp) &&
+ READ_ONCE(rnp->expmask) == 0;
+}
+
+/*
+ * Report the exit from RCU read-side critical section for the last task
+ * that queued itself during or before the current expedited preemptible-RCU
+ * grace period. This event is reported either to the rcu_node structure on
+ * which the task was queued or to one of that rcu_node structure's ancestors,
+ * recursively up the tree. (Calm down, calm down, we do the recursion
+ * iteratively!)
+ *
+ * Caller must hold the root rcu_node's exp_funnel_mutex.
+ */
+static void __maybe_unused rcu_report_exp_rnp(struct rcu_state *rsp,
+ struct rcu_node *rnp, bool wake)
+{
+ unsigned long flags;
+ unsigned long mask;
+
+ raw_spin_lock_irqsave(&rnp->lock, flags);
+ smp_mb__after_unlock_lock();
+ for (;;) {
+ if (!sync_rcu_preempt_exp_done(rnp)) {
+ raw_spin_unlock_irqrestore(&rnp->lock, flags);
+ break;
+ }
+ if (rnp->parent == NULL) {
+ raw_spin_unlock_irqrestore(&rnp->lock, flags);
+ if (wake) {
+ smp_mb(); /* EGP done before wake_up(). */
+ wake_up(&rsp->expedited_wq);
+ }
+ break;
+ }
+ mask = rnp->grpmask;
+ raw_spin_unlock(&rnp->lock); /* irqs remain disabled */
+ rnp = rnp->parent;
+ raw_spin_lock(&rnp->lock); /* irqs already disabled */
+ smp_mb__after_unlock_lock();
+ rnp->expmask &= ~mask;
+ }
+}
+
/* Common code for synchronize_{rcu,sched}_expedited() work-done checking. */
static bool sync_exp_work_done(struct rcu_state *rsp, struct rcu_node *rnp,
struct rcu_data *rdp,