Commit-ID: c91a8675b9cc697c725b6d97fcc7f157f4a989d0
Gitweb: https://git.kernel.org/tip/c91a8675b9cc697c725b6d97fcc7f157f4a989d0
Author: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
AuthorDate: Wed, 18 Apr 2018 11:11:39 -0700
Committer: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
CommitDate: Tue, 15 May 2018 10:29:18 -0700
rcu: Add accessor macros for the ->need_future_gp[] array
Accessors for the ->need_future_gp[] array are currently open-coded,
which makes them difficult to change. To improve maintainability, this
commit adds need_future_gp_mask() to compute the indexing mask from the
array size, need_future_gp_element() to access the element corresponding
to the specified grace-period number, and need_any_future_gp() to
determine if any future grace period is needed. This commit also applies
need_future_gp_element() to existing open-coded single-element accesses.
Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
Tested-by: Nicholas Piggin <npiggin@xxxxxxxxx>
---
kernel/rcu/tree.c | 16 +++++++---------
kernel/rcu/tree.h | 15 +++++++++++++++
kernel/rcu/tree_plugin.h | 2 +-
3 files changed, 23 insertions(+), 10 deletions(-)
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 4bbba17422cd..79fb99951a0c 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -718,11 +718,9 @@ static struct rcu_node *rcu_get_root(struct rcu_state *rsp)
static int rcu_future_needs_gp(struct rcu_state *rsp)
{
struct rcu_node *rnp = rcu_get_root(rsp);
- int idx = (READ_ONCE(rnp->completed) + 1) & 0x1;
- int *fp = &rnp->need_future_gp[idx];
lockdep_assert_irqs_disabled();
- return READ_ONCE(*fp);
+ return READ_ONCE(need_future_gp_element(rnp, rnp->completed));
}
/*
@@ -1699,7 +1697,7 @@ rcu_start_future_gp(struct rcu_node *rnp, struct rcu_data *rdp,
*/
c = rcu_cbs_completed(rdp->rsp, rnp);
trace_rcu_future_gp(rnp, rdp, c, TPS("Startleaf"));
- if (rnp->need_future_gp[c & 0x1]) {
+ if (need_future_gp_element(rnp, c)) {
trace_rcu_future_gp(rnp, rdp, c, TPS("Prestartleaf"));
goto out;
}
@@ -1711,7 +1709,7 @@ rcu_start_future_gp(struct rcu_node *rnp, struct rcu_data *rdp,
* current grace period, we don't need to explicitly start one.
*/
if (rnp->gpnum != rnp->completed) {
- rnp->need_future_gp[c & 0x1]++;
+ need_future_gp_element(rnp, c)++;
trace_rcu_future_gp(rnp, rdp, c, TPS("Startedleaf"));
goto out;
}
@@ -1737,13 +1735,13 @@ rcu_start_future_gp(struct rcu_node *rnp, struct rcu_data *rdp,
* If the needed for the required grace period is already
* recorded, trace and leave.
*/
- if (rnp_root->need_future_gp[c & 0x1]) {
+ if (need_future_gp_element(rnp_root, c)) {
trace_rcu_future_gp(rnp, rdp, c, TPS("Prestartedroot"));
goto unlock_out;
}
/* Record the need for the future grace period. */
- rnp_root->need_future_gp[c & 0x1]++;
+ need_future_gp_element(rnp_root, c)++;
/* If a grace period is not already in progress, start one. */
if (rnp_root->gpnum != rnp_root->completed) {
@@ -1771,8 +1769,8 @@ static int rcu_future_gp_cleanup(struct rcu_state *rsp, struct rcu_node *rnp)
int needmore;
struct rcu_data *rdp = this_cpu_ptr(rsp->rda);
- rnp->need_future_gp[c & 0x1] = 0;
- needmore = rnp->need_future_gp[(c + 1) & 0x1];
+ need_future_gp_element(rnp, c) = 0;
+ needmore = need_future_gp_element(rnp, c + 1);
trace_rcu_future_gp(rnp, rdp, c,
needmore ? TPS("CleanupMore") : TPS("Cleanup"));
return needmore;
diff --git a/kernel/rcu/tree.h b/kernel/rcu/tree.h
index f491ab4f2e8e..18b091474ffa 100644
--- a/kernel/rcu/tree.h
+++ b/kernel/rcu/tree.h
@@ -159,6 +159,21 @@ struct rcu_node {
wait_queue_head_t exp_wq[4];
} ____cacheline_internodealigned_in_smp;
+/* Accessors for ->need_future_gp[] array. */
+#define need_future_gp_mask() \
+ (ARRAY_SIZE(((struct rcu_node *)NULL)->need_future_gp) - 1)
+#define need_future_gp_element(rnp, c) \
+ ((rnp)->need_future_gp[(c) & need_future_gp_mask()])
+#define need_any_future_gp(rnp) \
+({ \
+ int __i; \
+ bool __nonzero = false; \
+ \
+ for (__i = 0; __i < ARRAY_SIZE((rnp)->need_future_gp); __i++) \
+ __nonzero = __nonzero || (rnp)->need_future_gp[__i]; \
+ __nonzero; \
+})
+
/*
* Bitmasks in an rcu_node cover the interval [grplo, grphi] of CPU IDs, and
* are indexed relative to this interval rather than the global CPU ID space.
diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index 84fbee4686d3..640ea927d8a4 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -1790,7 +1790,7 @@ static void rcu_nocb_gp_cleanup(struct swait_queue_head *sq)
*/
static void rcu_nocb_gp_set(struct rcu_node *rnp, int nrq)
{
- rnp->need_future_gp[(rnp->completed + 1) & 0x1] += nrq;
+ need_future_gp_element(rnp, rnp->completed + 1) += nrq;
}
static struct swait_queue_head *rcu_nocb_gp_get(struct rcu_node *rnp)
--
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