Mailing List Archive

From: Lai Jiangshan <jiangshan.ljs@antgroup.com>

Add wrappers accessing to t->rcu_read_unlock_special.b so that the
wrappers can be adapted for synching the value with the later-introduced
per-cpu rcu_preempt_count.

Cc: "Paul E. McKenney" <paulmck@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Lai Jiangshan <jiangshan.ljs@antgroup.com>
---
kernel/rcu/tree_exp.h | 2 +-
kernel/rcu/tree_plugin.h | 20 +++++++++++++-------
2 files changed, 14 insertions(+), 8 deletions(-)

diff --git a/kernel/rcu/tree_exp.h b/kernel/rcu/tree_exp.h
index 6b83537480b1..4e91414552e6 100644
--- a/kernel/rcu/tree_exp.h
+++ b/kernel/rcu/tree_exp.h
@@ -725,7 +725,7 @@ static void rcu_exp_handler(void *unused)
raw_spin_lock_irqsave_rcu_node(rnp, flags);
if (rnp->expmask & rdp->grpmask) {
WRITE_ONCE(rdp->cpu_no_qs.b.exp, true);
- t->rcu_read_unlock_special.b.exp_hint = true;
+ set_rcu_preempt_special(exp_hint);
}
raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
return;
diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index d899b4afc21c..3dbd5609185e 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -106,6 +106,14 @@ static void rcu_report_exp_rnp(struct rcu_node *rnp, bool wake);
static bool sync_rcu_exp_done(struct rcu_node *rnp);
static void rcu_read_unlock_special(struct task_struct *t);

+#define set_rcu_preempt_special(reason) do { \
+ WRITE_ONCE(current->rcu_read_unlock_special.b.reason, true); \
+ } while (0)
+
+#define clear_rcu_preempt_special(reason) do { \
+ WRITE_ONCE(current->rcu_read_unlock_special.b.reason, false); \
+ } while (0)
+
/*
* Tell them what RCU they are running.
*/
@@ -293,7 +301,7 @@ static void rcu_qs(void)
TPS("cpuqs"));
__this_cpu_write(rcu_data.cpu_no_qs.b.norm, false);
barrier(); /* Coordinate with rcu_flavor_sched_clock_irq(). */
- WRITE_ONCE(current->rcu_read_unlock_special.b.need_qs, false);
+ clear_rcu_preempt_special(need_qs);
}
}

@@ -325,7 +333,7 @@ void rcu_note_context_switch(bool preempt)
/* Possibly blocking in an RCU read-side critical section. */
rnp = rdp->mynode;
raw_spin_lock_rcu_node(rnp);
- t->rcu_read_unlock_special.b.blocked = true;
+ set_rcu_preempt_special(blocked);
t->rcu_blocked_node = rnp;

/*
@@ -399,7 +407,7 @@ void __rcu_read_lock(void)
if (IS_ENABLED(CONFIG_PROVE_LOCKING))
WARN_ON_ONCE(rcu_preempt_depth() > RCU_NEST_PMAX);
if (IS_ENABLED(CONFIG_RCU_STRICT_GRACE_PERIOD) && rcu_state.gp_kthread)
- WRITE_ONCE(current->rcu_read_unlock_special.b.need_qs, true);
+ set_rcu_preempt_special(need_qs);
barrier(); /* critical section after entry code. */
}
EXPORT_SYMBOL_GPL(__rcu_read_lock);
@@ -738,7 +746,7 @@ static void rcu_flavor_sched_clock_irq(int user)
__this_cpu_read(rcu_data.cpu_no_qs.b.norm) &&
!t->rcu_read_unlock_special.b.need_qs &&
time_after(jiffies, rcu_state.gp_start + HZ))
- t->rcu_read_unlock_special.b.need_qs = true;
+ set_rcu_preempt_special(need_qs);
}

/*
@@ -751,12 +759,10 @@ static void rcu_flavor_sched_clock_irq(int user)
*/
void exit_rcu(void)
{
- struct task_struct *t = current;
-
if (unlikely(!list_empty(&current->rcu_node_entry))) {
rcu_preempt_depth_set(1);
barrier();
- WRITE_ONCE(t->rcu_read_unlock_special.b.blocked, true);
+ set_rcu_preempt_special(blocked);
} else if (unlikely(rcu_preempt_depth())) {
rcu_preempt_depth_set(1);
} else {
--
2.19.1.6.gb485710b