[PATCH 04/10] rcu: Implement rcu_segcblist_is_offloaded() config dependent

Frederic Weisbecker
2020-05-13T16:47:32Z

This simplify the usage of this API and avoid checking the kernel
config from the callers.

Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Cc: Paul E. McKenney <paulmck@kernel.org>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Cc: Joel Fernandes <joel@joelfernandes.org>
---
include/linux/rcu_segcblist.h | 2 ++
kernel/rcu/rcu_segcblist.c | 2 ++
kernel/rcu/rcu_segcblist.h | 6 ++++++
kernel/rcu/tree.c | 21 +++++++--------------
4 files changed, 17 insertions(+), 14 deletions(-)

diff --git a/include/linux/rcu_segcblist.h b/include/linux/rcu_segcblist.h
index b36afe7b22c9..0ced0a0ecbcf 100644
--- a/include/linux/rcu_segcblist.h
+++ b/include/linux/rcu_segcblist.h
@@ -73,7 +73,9 @@ struct rcu_segcblist {
long len;
#endif
u8 enabled;
+#ifdef CONFIG_RCU_NOCB_CPU
u8 offloaded;
+#endif
};

#define RCU_SEGCBLIST_INITIALIZER(n) \
diff --git a/kernel/rcu/rcu_segcblist.c b/kernel/rcu/rcu_segcblist.c
index 9a0f66133b4b..d8ea2bef5574 100644
--- a/kernel/rcu/rcu_segcblist.c
+++ b/kernel/rcu/rcu_segcblist.c
@@ -166,6 +166,7 @@ void rcu_segcblist_disable(struct rcu_segcblist *rsclp)
rsclp->enabled = 0;
}

+#ifdef CONFIG_RCU_NOCB_CPU
/*
* Mark the specified rcu_segcblist structure as offloaded. This
* structure must be empty.
@@ -174,6 +175,7 @@ void rcu_segcblist_offload(struct rcu_segcblist *rsclp)
{
rsclp->offloaded = 1;
}
+#endif

/*
* Does the specified rcu_segcblist structure contain callbacks that
diff --git a/kernel/rcu/rcu_segcblist.h b/kernel/rcu/rcu_segcblist.h
index 5c293afc07b8..4c1503a82492 100644
--- a/kernel/rcu/rcu_segcblist.h
+++ b/kernel/rcu/rcu_segcblist.h
@@ -62,7 +62,11 @@ static inline bool rcu_segcblist_is_enabled(struct rcu_segcblist *rsclp)
/* Is the specified rcu_segcblist offloaded? */
static inline bool rcu_segcblist_is_offloaded(struct rcu_segcblist *rsclp)
{
+#ifdef CONFIG_RCU_NOCB_CPU
return rsclp->offloaded;
+#else
+ return false;
+#endif
}

/*
@@ -78,7 +82,9 @@ static inline bool rcu_segcblist_restempty(struct rcu_segcblist *rsclp, int seg)
void rcu_segcblist_inc_len(struct rcu_segcblist *rsclp);
void rcu_segcblist_init(struct rcu_segcblist *rsclp);
void rcu_segcblist_disable(struct rcu_segcblist *rsclp);
+#ifdef CONFIG_RCU_NOCB_CPU
void rcu_segcblist_offload(struct rcu_segcblist *rsclp);
+#endif
bool rcu_segcblist_ready_cbs(struct rcu_segcblist *rsclp);
bool rcu_segcblist_pend_cbs(struct rcu_segcblist *rsclp);
struct rcu_head *rcu_segcblist_first_cb(struct rcu_segcblist *rsclp);
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index d9a49cd6065a..804cf7dfff03 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -1401,8 +1401,7 @@ static bool __note_gp_changes(struct rcu_node *rnp, struct rcu_data *rdp)
{
bool ret = false;
bool need_qs;
- const bool offloaded = IS_ENABLED(CONFIG_RCU_NOCB_CPU) &&
- rcu_segcblist_is_offloaded(&rdp->cblist);
+ const bool offloaded = rcu_segcblist_is_offloaded(&rdp->cblist);

raw_lockdep_assert_held_rcu_node(rnp);

@@ -1790,8 +1789,7 @@ static void rcu_gp_cleanup(void)
needgp = true;
}
/* Advance CBs to reduce false positives below. */
- offloaded = IS_ENABLED(CONFIG_RCU_NOCB_CPU) &&
- rcu_segcblist_is_offloaded(&rdp->cblist);
+ offloaded = rcu_segcblist_is_offloaded(&rdp->cblist);
if ((offloaded || !rcu_accelerate_cbs(rnp, rdp)) && needgp) {
WRITE_ONCE(rcu_state.gp_flags, RCU_GP_FLAG_INIT);
WRITE_ONCE(rcu_state.gp_req_activity, jiffies);
@@ -1985,8 +1983,7 @@ rcu_report_qs_rdp(int cpu, struct rcu_data *rdp)
unsigned long flags;
unsigned long mask;
bool needwake = false;
- const bool offloaded = IS_ENABLED(CONFIG_RCU_NOCB_CPU) &&
- rcu_segcblist_is_offloaded(&rdp->cblist);
+ const bool offloaded = rcu_segcblist_is_offloaded(&rdp->cblist);
struct rcu_node *rnp;

rnp = rdp->mynode;
@@ -2153,8 +2150,7 @@ int rcutree_dead_cpu(unsigned int cpu)
static void rcu_do_batch(struct rcu_data *rdp)
{
unsigned long flags;
- const bool offloaded = IS_ENABLED(CONFIG_RCU_NOCB_CPU) &&
- rcu_segcblist_is_offloaded(&rdp->cblist);
+ const bool offloaded = rcu_segcblist_is_offloaded(&rdp->cblist);
struct rcu_head *rhp;
struct rcu_cblist rcl = RCU_CBLIST_INITIALIZER(rcl);
long bl, count;
@@ -2397,8 +2393,7 @@ static __latent_entropy void rcu_core(void)
unsigned long flags;
struct rcu_data *rdp = raw_cpu_ptr(&rcu_data);
struct rcu_node *rnp = rdp->mynode;
- const bool offloaded = IS_ENABLED(CONFIG_RCU_NOCB_CPU) &&
- rcu_segcblist_is_offloaded(&rdp->cblist);
+ const bool offloaded = rcu_segcblist_is_offloaded(&rdp->cblist);

if (cpu_is_offline(smp_processor_id()))
return;
@@ -2695,8 +2690,7 @@ __call_rcu(struct rcu_head *head, rcu_callback_t func)
rcu_segcblist_n_cbs(&rdp->cblist));

/* Go handle any RCU core processing required. */
- if (IS_ENABLED(CONFIG_RCU_NOCB_CPU) &&
- unlikely(rcu_segcblist_is_offloaded(&rdp->cblist))) {
+ if (unlikely(rcu_segcblist_is_offloaded(&rdp->cblist))) {
__call_rcu_nocb_wake(rdp, was_alldone, flags); /* unlocks */
} else {
__call_rcu_core(rdp, head, flags);
@@ -3243,8 +3237,7 @@ static int rcu_pending(int user)

/* Has RCU gone idle with this CPU needing another grace period? */
if (!gp_in_progress && rcu_segcblist_is_enabled(&rdp->cblist) &&
- (!IS_ENABLED(CONFIG_RCU_NOCB_CPU) ||
- !rcu_segcblist_is_offloaded(&rdp->cblist)) &&
+ !rcu_segcblist_is_offloaded(&rdp->cblist) &&
!rcu_segcblist_restempty(&rdp->cblist, RCU_NEXT_READY_TAIL))
return 1;

--
2.25.0