![Oleg Nesterov](/assets/img/avatar_default.png)
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>
8 lines
248 B
Makefile
8 lines
248 B
Makefile
obj-y += update.o sync.o
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obj-$(CONFIG_SRCU) += srcu.o
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obj-$(CONFIG_RCU_TORTURE_TEST) += rcutorture.o
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obj-$(CONFIG_TREE_RCU) += tree.o
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obj-$(CONFIG_PREEMPT_RCU) += tree.o
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obj-$(CONFIG_TREE_RCU_TRACE) += tree_trace.o
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obj-$(CONFIG_TINY_RCU) += tiny.o
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