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Subject[PATCH tip/core/rcu 01/21] rcu/nocb: Turn enabled/offload states into a common flag
Date
From: Frederic Weisbecker <frederic@kernel.org>

This commit gathers the rcu_segcblist ->enabled and ->offloaded property
field into a single ->flags bitmask to avoid further proliferation of
individual u8 fields in the structure. This change prepares for the
state formerly known as ->offloaded state to be modified at runtime.

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>
Cc: Neeraj Upadhyay <neeraju@codeaurora.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Inspired-by: Paul E. McKenney <paulmck@kernel.org>
Tested-by: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
include/linux/rcu_segcblist.h | 6 ++++--
kernel/rcu/rcu_segcblist.c | 6 +++---
kernel/rcu/rcu_segcblist.h | 23 +++++++++++++++++++++--
3 files changed, 28 insertions(+), 7 deletions(-)

diff --git a/include/linux/rcu_segcblist.h b/include/linux/rcu_segcblist.h
index 6c01f09..4714b02 100644
--- a/include/linux/rcu_segcblist.h
+++ b/include/linux/rcu_segcblist.h
@@ -63,6 +63,9 @@ struct rcu_cblist {
#define RCU_NEXT_TAIL 3
#define RCU_CBLIST_NSEGS 4

+#define SEGCBLIST_ENABLED BIT(0)
+#define SEGCBLIST_OFFLOADED BIT(1)
+
struct rcu_segcblist {
struct rcu_head *head;
struct rcu_head **tails[RCU_CBLIST_NSEGS];
@@ -73,8 +76,7 @@ struct rcu_segcblist {
long len;
#endif
long seglen[RCU_CBLIST_NSEGS];
- u8 enabled;
- u8 offloaded;
+ u8 flags;
};

#define RCU_SEGCBLIST_INITIALIZER(n) \
diff --git a/kernel/rcu/rcu_segcblist.c b/kernel/rcu/rcu_segcblist.c
index 094de25..406c67b 100644
--- a/kernel/rcu/rcu_segcblist.c
+++ b/kernel/rcu/rcu_segcblist.c
@@ -246,7 +246,7 @@ void rcu_segcblist_init(struct rcu_segcblist *rsclp)
rcu_segcblist_set_seglen(rsclp, i, 0);
}
rcu_segcblist_set_len(rsclp, 0);
- rsclp->enabled = 1;
+ rcu_segcblist_set_flags(rsclp, SEGCBLIST_ENABLED);
}

/*
@@ -257,7 +257,7 @@ void rcu_segcblist_disable(struct rcu_segcblist *rsclp)
{
WARN_ON_ONCE(!rcu_segcblist_empty(rsclp));
WARN_ON_ONCE(rcu_segcblist_n_cbs(rsclp));
- rsclp->enabled = 0;
+ rcu_segcblist_clear_flags(rsclp, SEGCBLIST_ENABLED);
}

/*
@@ -266,7 +266,7 @@ void rcu_segcblist_disable(struct rcu_segcblist *rsclp)
*/
void rcu_segcblist_offload(struct rcu_segcblist *rsclp)
{
- rsclp->offloaded = 1;
+ rcu_segcblist_set_flags(rsclp, SEGCBLIST_OFFLOADED);
}

/*
diff --git a/kernel/rcu/rcu_segcblist.h b/kernel/rcu/rcu_segcblist.h
index 18e101d..ff372db 100644
--- a/kernel/rcu/rcu_segcblist.h
+++ b/kernel/rcu/rcu_segcblist.h
@@ -53,19 +53,38 @@ static inline long rcu_segcblist_n_cbs(struct rcu_segcblist *rsclp)
#endif
}

+static inline void rcu_segcblist_set_flags(struct rcu_segcblist *rsclp,
+ int flags)
+{
+ rsclp->flags |= flags;
+}
+
+static inline void rcu_segcblist_clear_flags(struct rcu_segcblist *rsclp,
+ int flags)
+{
+ rsclp->flags &= ~flags;
+}
+
+static inline bool rcu_segcblist_test_flags(struct rcu_segcblist *rsclp,
+ int flags)
+{
+ return READ_ONCE(rsclp->flags) & flags;
+}
+
/*
* Is the specified rcu_segcblist enabled, for example, not corresponding
* to an offline CPU?
*/
static inline bool rcu_segcblist_is_enabled(struct rcu_segcblist *rsclp)
{
- return rsclp->enabled;
+ return rcu_segcblist_test_flags(rsclp, SEGCBLIST_ENABLED);
}

/* Is the specified rcu_segcblist offloaded? */
static inline bool rcu_segcblist_is_offloaded(struct rcu_segcblist *rsclp)
{
- return IS_ENABLED(CONFIG_RCU_NOCB_CPU) && rsclp->offloaded;
+ return IS_ENABLED(CONFIG_RCU_NOCB_CPU) &&
+ rcu_segcblist_test_flags(rsclp, SEGCBLIST_OFFLOADED);
}

/*
--
2.9.5
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