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Subject[tip:core/rcu] rcu: Replace the rcu_barrier enum with pointer to call_rcu*() function
Commit-ID:  135c8aea557cf53abe6c8847e286d01442124193
Gitweb: http://git.kernel.org/tip/135c8aea557cf53abe6c8847e286d01442124193
Author: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
AuthorDate: Mon, 28 Sep 2009 21:50:21 -0700
Committer: Ingo Molnar <mingo@elte.hu>
CommitDate: Mon, 5 Oct 2009 21:02:05 +0200

rcu: Replace the rcu_barrier enum with pointer to call_rcu*() function

The rcu_barrier enum causes several problems:

(1) you have to define the enum somewhere, and there is no
convenient place,

(2) the difference between TREE_RCU and TREE_PREEMPT_RCU causes
problems when you need to map from rcu_barrier enum to struct
rcu_state,

(3) the switch statement are large, and

(4) TINY_RCU really needs a different rcu_barrier() than do the
treercu implementations.

So replace it with a functionally equivalent but cleaner function
pointer abstraction.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Cc: laijs@cn.fujitsu.com
Cc: dipankar@in.ibm.com
Cc: akpm@linux-foundation.org
Cc: josh@joshtriplett.org
Cc: dvhltc@us.ibm.com
Cc: niv@us.ibm.com
Cc: peterz@infradead.org
Cc: rostedt@goodmis.org
Cc: Valdis.Kletnieks@vt.edu
Cc: dhowells@redhat.com
LKML-Reference: <12541998232366-git-send-email->
Signed-off-by: Ingo Molnar <mingo@elte.hu>


---
kernel/rcupdate.c | 32 ++++++++++----------------------
1 files changed, 10 insertions(+), 22 deletions(-)
diff --git a/kernel/rcupdate.c b/kernel/rcupdate.c
index 4a189ea..e432422 100644
--- a/kernel/rcupdate.c
+++ b/kernel/rcupdate.c
@@ -53,12 +53,6 @@ struct lockdep_map rcu_lock_map =
EXPORT_SYMBOL_GPL(rcu_lock_map);
#endif

-enum rcu_barrier {
- RCU_BARRIER_STD,
- RCU_BARRIER_BH,
- RCU_BARRIER_SCHED,
-};
-
static DEFINE_PER_CPU(struct rcu_head, rcu_barrier_head) = {NULL};
static atomic_t rcu_barrier_cpu_count;
static DEFINE_MUTEX(rcu_barrier_mutex);
@@ -184,19 +178,12 @@ static void rcu_barrier_func(void *type)
{
int cpu = smp_processor_id();
struct rcu_head *head = &per_cpu(rcu_barrier_head, cpu);
+ void (*call_rcu_func)(struct rcu_head *head,
+ void (*func)(struct rcu_head *head));

atomic_inc(&rcu_barrier_cpu_count);
- switch ((enum rcu_barrier)type) {
- case RCU_BARRIER_STD:
- call_rcu(head, rcu_barrier_callback);
- break;
- case RCU_BARRIER_BH:
- call_rcu_bh(head, rcu_barrier_callback);
- break;
- case RCU_BARRIER_SCHED:
- call_rcu_sched(head, rcu_barrier_callback);
- break;
- }
+ call_rcu_func = type;
+ call_rcu_func(head, rcu_barrier_callback);
}

static inline void wait_migrated_callbacks(void)
@@ -209,7 +196,8 @@ static inline void wait_migrated_callbacks(void)
* Orchestrate the specified type of RCU barrier, waiting for all
* RCU callbacks of the specified type to complete.
*/
-static void _rcu_barrier(enum rcu_barrier type)
+static void _rcu_barrier(void (*call_rcu_func)(struct rcu_head *head,
+ void (*func)(struct rcu_head *head)))
{
BUG_ON(in_interrupt());
/* Take cpucontrol mutex to protect against CPU hotplug */
@@ -225,7 +213,7 @@ static void _rcu_barrier(enum rcu_barrier type)
* early.
*/
atomic_set(&rcu_barrier_cpu_count, 1);
- on_each_cpu(rcu_barrier_func, (void *)type, 1);
+ on_each_cpu(rcu_barrier_func, (void *)call_rcu_func, 1);
if (atomic_dec_and_test(&rcu_barrier_cpu_count))
complete(&rcu_barrier_completion);
wait_for_completion(&rcu_barrier_completion);
@@ -238,7 +226,7 @@ static void _rcu_barrier(enum rcu_barrier type)
*/
void rcu_barrier(void)
{
- _rcu_barrier(RCU_BARRIER_STD);
+ _rcu_barrier(call_rcu);
}
EXPORT_SYMBOL_GPL(rcu_barrier);

@@ -247,7 +235,7 @@ EXPORT_SYMBOL_GPL(rcu_barrier);
*/
void rcu_barrier_bh(void)
{
- _rcu_barrier(RCU_BARRIER_BH);
+ _rcu_barrier(call_rcu_bh);
}
EXPORT_SYMBOL_GPL(rcu_barrier_bh);

@@ -256,7 +244,7 @@ EXPORT_SYMBOL_GPL(rcu_barrier_bh);
*/
void rcu_barrier_sched(void)
{
- _rcu_barrier(RCU_BARRIER_SCHED);
+ _rcu_barrier(call_rcu_sched);
}
EXPORT_SYMBOL_GPL(rcu_barrier_sched);


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