rcu: simplify the usage of percpu data
&percpu_data is compatible with allocated percpu data.
And we use it and remove the "->rda[NR_CPUS]" array, saving significant
storage on systems with large numbers of CPUs. This does add an additional
level of indirection and thus an additional cache line referenced, but
because ->rda is not used on the read side, this is OK.
Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Reviewed-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index d5bc439..5b1c3c2 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -712,7 +712,7 @@
rcu_start_gp(struct rcu_state *rsp, unsigned long flags)
__releases(rcu_get_root(rsp)->lock)
{
- struct rcu_data *rdp = rsp->rda[smp_processor_id()];
+ struct rcu_data *rdp = this_cpu_ptr(rsp->rda);
struct rcu_node *rnp = rcu_get_root(rsp);
if (!cpu_needs_another_gp(rsp, rdp) || rsp->fqs_active) {
@@ -960,7 +960,7 @@
static void rcu_send_cbs_to_orphanage(struct rcu_state *rsp)
{
int i;
- struct rcu_data *rdp = rsp->rda[smp_processor_id()];
+ struct rcu_data *rdp = this_cpu_ptr(rsp->rda);
if (rdp->nxtlist == NULL)
return; /* irqs disabled, so comparison is stable. */
@@ -984,7 +984,7 @@
struct rcu_data *rdp;
raw_spin_lock_irqsave(&rsp->onofflock, flags);
- rdp = rsp->rda[smp_processor_id()];
+ rdp = this_cpu_ptr(rsp->rda);
if (rsp->orphan_cbs_list == NULL) {
raw_spin_unlock_irqrestore(&rsp->onofflock, flags);
return;
@@ -1007,7 +1007,7 @@
unsigned long flags;
unsigned long mask;
int need_report = 0;
- struct rcu_data *rdp = rsp->rda[cpu];
+ struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu);
struct rcu_node *rnp;
/* Exclude any attempts to start a new grace period. */
@@ -1226,7 +1226,8 @@
cpu = rnp->grplo;
bit = 1;
for (; cpu <= rnp->grphi; cpu++, bit <<= 1) {
- if ((rnp->qsmask & bit) != 0 && f(rsp->rda[cpu]))
+ if ((rnp->qsmask & bit) != 0 &&
+ f(per_cpu_ptr(rsp->rda, cpu)))
mask |= bit;
}
if (mask != 0) {
@@ -1402,7 +1403,7 @@
* a quiescent state betweentimes.
*/
local_irq_save(flags);
- rdp = rsp->rda[smp_processor_id()];
+ rdp = this_cpu_ptr(rsp->rda);
rcu_process_gp_end(rsp, rdp);
check_for_new_grace_period(rsp, rdp);
@@ -1701,7 +1702,7 @@
{
unsigned long flags;
int i;
- struct rcu_data *rdp = rsp->rda[cpu];
+ struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu);
struct rcu_node *rnp = rcu_get_root(rsp);
/* Set up local state, ensuring consistent view of global state. */
@@ -1729,7 +1730,7 @@
{
unsigned long flags;
unsigned long mask;
- struct rcu_data *rdp = rsp->rda[cpu];
+ struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu);
struct rcu_node *rnp = rcu_get_root(rsp);
/* Set up local state, ensuring consistent view of global state. */
@@ -1865,7 +1866,8 @@
/*
* Helper function for rcu_init() that initializes one rcu_state structure.
*/
-static void __init rcu_init_one(struct rcu_state *rsp)
+static void __init rcu_init_one(struct rcu_state *rsp,
+ struct rcu_data __percpu *rda)
{
static char *buf[] = { "rcu_node_level_0",
"rcu_node_level_1",
@@ -1918,37 +1920,23 @@
}
}
+ rsp->rda = rda;
rnp = rsp->level[NUM_RCU_LVLS - 1];
for_each_possible_cpu(i) {
while (i > rnp->grphi)
rnp++;
- rsp->rda[i]->mynode = rnp;
+ per_cpu_ptr(rsp->rda, i)->mynode = rnp;
rcu_boot_init_percpu_data(i, rsp);
}
}
-/*
- * Helper macro for __rcu_init() and __rcu_init_preempt(). To be used
- * nowhere else! Assigns leaf node pointers into each CPU's rcu_data
- * structure.
- */
-#define RCU_INIT_FLAVOR(rsp, rcu_data) \
-do { \
- int i; \
- \
- for_each_possible_cpu(i) { \
- (rsp)->rda[i] = &per_cpu(rcu_data, i); \
- } \
- rcu_init_one(rsp); \
-} while (0)
-
void __init rcu_init(void)
{
int cpu;
rcu_bootup_announce();
- RCU_INIT_FLAVOR(&rcu_sched_state, rcu_sched_data);
- RCU_INIT_FLAVOR(&rcu_bh_state, rcu_bh_data);
+ rcu_init_one(&rcu_sched_state, &rcu_sched_data);
+ rcu_init_one(&rcu_bh_state, &rcu_bh_data);
__rcu_init_preempt();
open_softirq(RCU_SOFTIRQ, rcu_process_callbacks);
