diff options
author | Oleg Nesterov | 2015-08-21 19:42:44 +0200 |
---|---|---|
committer | Paul E. McKenney | 2015-10-06 11:25:04 -0700 |
commit | cc44ca848f5e517aeca9f5eabbe13609a3f71450 (patch) | |
tree | 4380962c131d6585f347aee962b0280176ae4bdd /kernel/rcu/Makefile | |
parent | 3836f5337f74fedc15981688c3c31dbf4293ae84 (diff) |
rcu: Create rcu_sync infrastructure
The rcu_sync infrastructure can be thought of as infrastructure to be
used to implement reader-writer primitives having extremely lightweight
readers during times when there are no writers. The first use is in
the percpu_rwsem used by the VFS subsystem.
This infrastructure is functionally equivalent to
struct rcu_sync_struct {
atomic_t counter;
};
/* Check possibility of fast-path read-side operations. */
static inline bool rcu_sync_is_idle(struct rcu_sync_struct *rss)
{
return atomic_read(&rss->counter) == 0;
}
/* Tell readers to use slowpaths. */
static inline void rcu_sync_enter(struct rcu_sync_struct *rss)
{
atomic_inc(&rss->counter);
synchronize_sched();
}
/* Allow readers to once again use fastpaths. */
static inline void rcu_sync_exit(struct rcu_sync_struct *rss)
{
synchronize_sched();
atomic_dec(&rss->counter);
}
The main difference is that it records the state and only calls
synchronize_sched() if required. At least some of the calls to
synchronize_sched() will be optimized away when rcu_sync_enter() and
rcu_sync_exit() are invoked repeatedly in quick succession.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Diffstat (limited to 'kernel/rcu/Makefile')
-rw-r--r-- | kernel/rcu/Makefile | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/kernel/rcu/Makefile b/kernel/rcu/Makefile index 50a808424b06..61a16569ffbf 100644 --- a/kernel/rcu/Makefile +++ b/kernel/rcu/Makefile @@ -1,4 +1,4 @@ -obj-y += update.o +obj-y += update.o sync.o obj-$(CONFIG_SRCU) += srcu.o obj-$(CONFIG_RCU_TORTURE_TEST) += rcutorture.o obj-$(CONFIG_TREE_RCU) += tree.o |