+++ /dev/null
-Userspace RCU API
-by Mathieu Desnoyers and Paul E. McKenney
-
-
-void rcu_init(void);
-
- This must be called before any of the following functions
- are invoked.
-
-void rcu_read_lock(void);
-
- Begin an RCU read-side critical section. These critical
- sections may be nested.
-
-void rcu_read_unlock(void);
-
- End an RCU read-side critical section.
-
-void rcu_register_thread(void);
-
- Each thread must invoke this function before its first call to
- rcu_read_lock(). Threads that never call rcu_read_lock() need
- not invoke this function. In addition, rcu-bp ("bullet proof"
- RCU) does not require any thread to invoke rcu_register_thread().
-
-void rcu_unregister_thread(void);
-
- Each thread that invokes rcu_register_thread() must invoke
- rcu_unregister_thread() before invoking pthread_exit()
- or before returning from its top-level function.
-
-void synchronize_rcu(void);
-
- Wait until every pre-existing RCU read-side critical section
- has completed. Note that this primitive will not necessarily
- wait for RCU read-side critical sections that have not yet
- started: this is not a reader-writer lock. The duration
- actually waited is called an RCU grace period.
-
-void call_rcu(struct rcu_head *head,
- void (*func)(struct rcu_head *head));
-
- Registers the callback indicated by "head". This means
- that "func" will be invoked after the end of a future
- RCU grace period. The rcu_head structure referenced
- by "head" will normally be a field in a larger RCU-protected
- structure. A typical implementation of "func" is as
- follows:
-
- void func(struct rcu_head *head)
- {
- struct foo *p = container_of(head, struct foo, rcu);
-
- free(p);
- }
-
- This RCU callback function can be registered as follows
- given a pointer "p" to the enclosing structure:
-
- call_rcu(&p->rcu, func);
-
- call_rcu should be called from registered RCU read-side threads.
- For the QSBR flavor, the caller should be online.
-
-void rcu_barrier(void);
-
- Wait for all call_rcu() work initiated prior to rcu_barrier() by
- _any_ thread on the system to have completed before rcu_barrier()
- returns. rcu_barrier() should never be called from a call_rcu()
- thread. This function can be used, for instance, to ensure that
- all memory reclaim involving a shared object has completed
- before allowing dlclose() of this shared object to complete.
-
-struct call_rcu_data *create_call_rcu_data(unsigned long flags,
- int cpu_affinity);
-
- Returns a handle that can be passed to the following
- primitives. The "flags" argument can be zero, or can be
- URCU_CALL_RCU_RT if the worker threads associated with the
- new helper thread are to get real-time response. The argument
- "cpu_affinity" specifies a cpu on which the call_rcu thread should
- be affined to. It is ignored if negative.
-
-void call_rcu_data_free(struct call_rcu_data *crdp);
-
- Terminates a call_rcu() helper thread and frees its associated
- data. The caller must have ensured that this thread is no longer
- in use, for example, by passing NULL to set_thread_call_rcu_data()
- and set_cpu_call_rcu_data() as required.
-
-struct call_rcu_data *get_default_call_rcu_data(void);
-
- Returns the handle for the default call_rcu() helper thread.
- Creates it if necessary.
-
-struct call_rcu_data *get_cpu_call_rcu_data(int cpu);
-
- Returns the handle for the current cpu's call_rcu() helper
- thread, or NULL if the current CPU has no helper thread
- currently assigned. The call to this function and use of the
- returned call_rcu_data should be protected by RCU read-side
- lock.
-
-struct call_rcu_data *get_thread_call_rcu_data(void);
-
- Returns the handle for the current thread's hard-assigned
- call_rcu() helper thread, or NULL if the current thread is
- instead using a per-CPU or the default helper thread.
-
-struct call_rcu_data *get_call_rcu_data(void);
-
- Returns the handle for the current thread's call_rcu() helper
- thread, which is either, in increasing order of preference:
- per-thread hard-assigned helper thread, per-cpu helper thread,
- or default helper thread. get_call_rcu_data should be called
- from registered RCU read-side threads. For the QSBR flavor, the
- caller should be online.
-
-pthread_t get_call_rcu_thread(struct call_rcu_data *crdp);
-
- Returns the helper thread's pthread identifier linked to a call
- rcu helper thread data.
-
-void set_thread_call_rcu_data(struct call_rcu_data *crdp);
-
- Sets the current thread's hard-assigned call_rcu() helper to the
- handle specified by "crdp". Note that "crdp" can be NULL to
- disassociate this thread from its helper. Once a thread is
- disassociated from its helper, further call_rcu() invocations
- use the current CPU's helper if there is one and the default
- helper otherwise.
-
-int set_cpu_call_rcu_data(int cpu, struct call_rcu_data *crdp);
-
- Sets the specified CPU's call_rcu() helper to the handle
- specified by "crdp". Again, "crdp" can be NULL to disassociate
- this CPU from its helper thread. Once a CPU has been
- disassociated from its helper, further call_rcu() invocations
- that would otherwise have used this CPU's helper will instead
- use the default helper. The caller must wait for a grace-period
- to pass between return from set_cpu_call_rcu_data() and call to
- call_rcu_data_free() passing the previous call rcu data as
- argument.
-
-int create_all_cpu_call_rcu_data(unsigned long flags)
-
- Creates a separate call_rcu() helper thread for each CPU.
- After this primitive is invoked, the global default call_rcu()
- helper thread will not be called.
-
- The set_thread_call_rcu_data(), set_cpu_call_rcu_data(), and
- create_all_cpu_call_rcu_data() functions may be combined to set up
- pretty much any desired association between worker and call_rcu()
- helper threads. If a given executable calls only call_rcu(),
- then that executable will have only the single global default
- call_rcu() helper thread. This will suffice in most cases.
-
-void free_all_cpu_call_rcu_data(void);
-
- Clean up all the per-CPU call_rcu threads. Should be paired with
- create_all_cpu_call_rcu_data() to perform teardown. Note that
- this function invokes synchronize_rcu() internally, so the
- caller should be careful not to hold mutexes (or mutexes within a
- dependency chain) that are also taken within a RCU read-side
- critical section, or in a section where QSBR threads are online.
-
-void call_rcu_after_fork_child(void);
-
- Should be used as pthread_atfork() handler for programs using
- call_rcu and performing fork() or clone() without a following
- exec().
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