rcu: Per-CPU operation cleanups to rcu_*_qs() functions
The rcu_bh_qs(), rcu_preempt_qs(), and rcu_sched_qs() functions use
old-style per-CPU variable access and write to ->passed_quiesce even
if it is already set. This commit therefore updates to use the new-style
per-CPU variable access functions and avoids the spurious writes.
This commit also eliminates the "cpu" argument to these functions because
they are always invoked on the indicated CPU.
Reported-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index 132e1e34..2fab0e3 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -261,8 +261,8 @@
/* Internal to kernel */
void rcu_init(void);
-void rcu_sched_qs(int cpu);
-void rcu_bh_qs(int cpu);
+void rcu_sched_qs(void);
+void rcu_bh_qs(void);
void rcu_check_callbacks(int cpu, int user);
struct notifier_block;
void rcu_idle_enter(void);
diff --git a/include/linux/rcutiny.h b/include/linux/rcutiny.h
index d40a6a4..38cc5b1 100644
--- a/include/linux/rcutiny.h
+++ b/include/linux/rcutiny.h
@@ -80,7 +80,7 @@
static inline void rcu_note_context_switch(int cpu)
{
- rcu_sched_qs(cpu);
+ rcu_sched_qs();
}
/*
diff --git a/kernel/rcu/tiny.c b/kernel/rcu/tiny.c
index 717f008..61b8d2c 100644
--- a/kernel/rcu/tiny.c
+++ b/kernel/rcu/tiny.c
@@ -72,7 +72,7 @@
current->pid, current->comm,
idle->pid, idle->comm); /* must be idle task! */
}
- rcu_sched_qs(0); /* implies rcu_bh_qsctr_inc(0) */
+ rcu_sched_qs(); /* implies rcu_bh_inc() */
barrier();
rcu_dynticks_nesting = newval;
}
@@ -217,7 +217,7 @@
* are at it, given that any rcu quiescent state is also an rcu_bh
* quiescent state. Use "+" instead of "||" to defeat short circuiting.
*/
-void rcu_sched_qs(int cpu)
+void rcu_sched_qs(void)
{
unsigned long flags;
@@ -231,7 +231,7 @@
/*
* Record an rcu_bh quiescent state.
*/
-void rcu_bh_qs(int cpu)
+void rcu_bh_qs(void)
{
unsigned long flags;
@@ -251,9 +251,9 @@
{
RCU_TRACE(check_cpu_stalls());
if (user || rcu_is_cpu_rrupt_from_idle())
- rcu_sched_qs(cpu);
+ rcu_sched_qs();
else if (!in_softirq())
- rcu_bh_qs(cpu);
+ rcu_bh_qs();
if (user)
rcu_note_voluntary_context_switch(current);
}
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index c880f53..4c34062 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -188,22 +188,24 @@
* one since the start of the grace period, this just sets a flag.
* The caller must have disabled preemption.
*/
-void rcu_sched_qs(int cpu)
+void rcu_sched_qs(void)
{
- struct rcu_data *rdp = &per_cpu(rcu_sched_data, cpu);
-
- if (rdp->passed_quiesce == 0)
- trace_rcu_grace_period(TPS("rcu_sched"), rdp->gpnum, TPS("cpuqs"));
- rdp->passed_quiesce = 1;
+ if (!__this_cpu_read(rcu_sched_data.passed_quiesce)) {
+ trace_rcu_grace_period(TPS("rcu_sched"),
+ __this_cpu_read(rcu_sched_data.gpnum),
+ TPS("cpuqs"));
+ __this_cpu_write(rcu_sched_data.passed_quiesce, 1);
+ }
}
-void rcu_bh_qs(int cpu)
+void rcu_bh_qs(void)
{
- struct rcu_data *rdp = &per_cpu(rcu_bh_data, cpu);
-
- if (rdp->passed_quiesce == 0)
- trace_rcu_grace_period(TPS("rcu_bh"), rdp->gpnum, TPS("cpuqs"));
- rdp->passed_quiesce = 1;
+ if (!__this_cpu_read(rcu_bh_data.passed_quiesce)) {
+ trace_rcu_grace_period(TPS("rcu_bh"),
+ __this_cpu_read(rcu_bh_data.gpnum),
+ TPS("cpuqs"));
+ __this_cpu_write(rcu_bh_data.passed_quiesce, 1);
+ }
}
static DEFINE_PER_CPU(int, rcu_sched_qs_mask);
@@ -278,7 +280,7 @@
void rcu_note_context_switch(int cpu)
{
trace_rcu_utilization(TPS("Start context switch"));
- rcu_sched_qs(cpu);
+ rcu_sched_qs();
rcu_preempt_note_context_switch(cpu);
if (unlikely(raw_cpu_read(rcu_sched_qs_mask)))
rcu_momentary_dyntick_idle();
@@ -2395,8 +2397,8 @@
* at least not while the corresponding CPU is online.
*/
- rcu_sched_qs(cpu);
- rcu_bh_qs(cpu);
+ rcu_sched_qs();
+ rcu_bh_qs();
} else if (!in_softirq()) {
@@ -2407,7 +2409,7 @@
* critical section, so note it.
*/
- rcu_bh_qs(cpu);
+ rcu_bh_qs();
}
rcu_preempt_check_callbacks(cpu);
if (rcu_pending(cpu))
diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index 0981c0c..25e692a 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -158,14 +158,16 @@
* As with the other rcu_*_qs() functions, callers to this function
* must disable preemption.
*/
-static void rcu_preempt_qs(int cpu)
+static void rcu_preempt_qs(void)
{
- struct rcu_data *rdp = &per_cpu(rcu_preempt_data, cpu);
-
- if (rdp->passed_quiesce == 0)
- trace_rcu_grace_period(TPS("rcu_preempt"), rdp->gpnum, TPS("cpuqs"));
- rdp->passed_quiesce = 1;
- current->rcu_read_unlock_special.b.need_qs = false;
+ if (!__this_cpu_read(rcu_preempt_data.passed_quiesce)) {
+ trace_rcu_grace_period(TPS("rcu_preempt"),
+ __this_cpu_read(rcu_preempt_data.gpnum),
+ TPS("cpuqs"));
+ __this_cpu_write(rcu_preempt_data.passed_quiesce, 1);
+ barrier(); /* Coordinate with rcu_preempt_check_callbacks(). */
+ current->rcu_read_unlock_special.b.need_qs = false;
+ }
}
/*
@@ -256,7 +258,7 @@
* grace period, then the fact that the task has been enqueued
* means that we continue to block the current grace period.
*/
- rcu_preempt_qs(cpu);
+ rcu_preempt_qs();
}
/*
@@ -352,7 +354,7 @@
*/
special = t->rcu_read_unlock_special;
if (special.b.need_qs) {
- rcu_preempt_qs(smp_processor_id());
+ rcu_preempt_qs();
if (!t->rcu_read_unlock_special.s) {
local_irq_restore(flags);
return;
@@ -651,11 +653,12 @@
struct task_struct *t = current;
if (t->rcu_read_lock_nesting == 0) {
- rcu_preempt_qs(cpu);
+ rcu_preempt_qs();
return;
}
if (t->rcu_read_lock_nesting > 0 &&
- per_cpu(rcu_preempt_data, cpu).qs_pending)
+ per_cpu(rcu_preempt_data, cpu).qs_pending &&
+ !per_cpu(rcu_preempt_data, cpu).passed_quiesce)
t->rcu_read_unlock_special.b.need_qs = true;
}
diff --git a/kernel/softirq.c b/kernel/softirq.c
index 5918d22..348ec76 100644
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -278,7 +278,7 @@
pending >>= softirq_bit;
}
- rcu_bh_qs(smp_processor_id());
+ rcu_bh_qs();
local_irq_disable();
pending = local_softirq_pending();