Add rcu_flavor

[urcu.git] / API.txt

diff --git a/API.txt b/API.txt
index 162ca9397bedb715d264fc16f237fff667868ce2..72430f7b248565ff2508cac3fde7d03914e50810 100644 (file)
--- a/API.txt
+++ b/API.txt
@@ -16,14 +16,14 @@ void rcu_read_unlock(void);
 
        End an RCU read-side critical section.
 
-void rcu_register_thread(void)
+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)
+void rcu_unregister_thread(void);
 
        Each thread that invokes rcu_register_thread() must invoke
        rcu_unregister_thread() before invoking pthread_exit()
@@ -59,12 +59,18 @@ void call_rcu(struct rcu_head *head,
 
                call_rcu(&p->rcu, func);
 
-struct call_rcu_data *create_call_rcu_data(unsigned long flags);
+       call_rcu should be called from registered RCU read-side threads.
+       For the QSBR flavor, the caller should be online.
+
+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.
+       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.
 
 struct call_rcu_data *get_default_call_rcu_data(void);
 
@@ -74,6 +80,28 @@ struct call_rcu_data *get_call_rcu_data(void);
 
        Returns the handle of the current thread's call_rcu() helper
        thread, which might well be the 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.
+
+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);
 
@@ -81,6 +109,18 @@ struct call_rcu_data *get_thread_call_rcu_data(void);
        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.
+
+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
@@ -97,7 +137,10 @@ int set_cpu_call_rcu_data(int cpu, struct call_rcu_data *crdp);
        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.
+       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)
 
@@ -112,9 +155,17 @@ int create_all_cpu_call_rcu_data(unsigned long flags)
        then that executable will have only the single global default
        call_rcu() helper thread.  This will suffice in most cases.
 
-void call_rcu_data_free(struct call_rcu_data *crdp)
+void free_all_cpu_call_rcu_data(void);
 
-       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.
+       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().