Commit | Line | Data |
---|---|---|
26ba798a PM |
1 | Userspace RCU API |
2 | by Mathieu Desnoyers and Paul E. McKenney | |
3 | ||
4 | ||
5 | void rcu_init(void); | |
6 | ||
7 | This must be called before any of the following functions | |
8 | are invoked. | |
9 | ||
10 | void rcu_read_lock(void); | |
11 | ||
12 | Begin an RCU read-side critical section. These critical | |
13 | sections may be nested. | |
14 | ||
15 | void rcu_read_unlock(void); | |
16 | ||
17 | End an RCU read-side critical section. | |
18 | ||
19 | void rcu_register_thread(void) | |
20 | ||
21 | Each thread must invoke this function before its first call to | |
22 | rcu_read_lock(). Threads that never call rcu_read_lock() need | |
23 | not invoke this function. In addition, rcu-bp ("bullet proof" | |
24 | RCU) does not require any thread to invoke rcu_register_thread(). | |
25 | ||
26 | void rcu_unregister_thread(void) | |
27 | ||
28 | Each thread that invokes rcu_register_thread() must invoke | |
29 | rcu_unregister_thread() before invoking pthread_exit() | |
30 | or before returning from its top-level function. | |
31 | ||
32 | void synchronize_rcu(void); | |
33 | ||
34 | Wait until every pre-existing RCU read-side critical section | |
35 | has completed. Note that this primitive will not necessarily | |
36 | wait for RCU read-side critical sections that have not yet | |
37 | started: this is not a reader-writer lock. The duration | |
38 | actually waited is called an RCU grace period. | |
39 | ||
40 | void call_rcu(struct rcu_head *head, | |
41 | void (*func)(struct rcu_head *head)); | |
42 | ||
43 | Registers the callback indicated by "head". This means | |
44 | that "func" will be invoked after the end of a future | |
45 | RCU grace period. The rcu_head structure referenced | |
46 | by "head" will normally be a field in a larger RCU-protected | |
47 | structure. A typical implementation of "func" is as | |
48 | follows: | |
49 | ||
50 | void func(struct rcu_head *head) | |
51 | { | |
52 | struct foo *p = container_of(head, struct foo, rcu); | |
53 | ||
54 | free(p); | |
55 | } | |
56 | ||
57 | This RCU callback function can be registered as follows | |
58 | given a pointer "p" to the enclosing structure: | |
59 | ||
60 | call_rcu(&p->rcu, func); | |
61 | ||
62 | struct call_rcu_data *create_call_rcu_data(unsigned long flags); | |
63 | ||
64 | Returns a handle that can be passed to the following | |
65 | primitives. The "flags" argument can be zero, or can be | |
66 | URCU_CALL_RCU_RT if the worker threads associated with the | |
67 | new helper thread are to get real-time response. | |
68 | ||
69 | struct call_rcu_data *get_default_call_rcu_data(void); | |
70 | ||
71 | Returns the handle of the default call_rcu() helper thread. | |
72 | ||
73 | struct call_rcu_data *get_call_rcu_data(void); | |
74 | ||
75 | Returns the handle of the current thread's call_rcu() helper | |
76 | thread, which might well be the default helper thread. | |
77 | ||
78 | struct call_rcu_data *get_thread_call_rcu_data(void); | |
79 | ||
80 | Returns the handle for the current thread's hard-assigned | |
81 | call_rcu() helper thread, or NULL if the current thread is | |
82 | instead using a per-CPU or the default helper thread. | |
83 | ||
84 | void set_thread_call_rcu_data(struct call_rcu_data *crdp); | |
85 | ||
86 | Sets the current thread's hard-assigned call_rcu() helper to the | |
87 | handle specified by "crdp". Note that "crdp" can be NULL to | |
88 | disassociate this thread from its helper. Once a thread is | |
89 | disassociated from its helper, further call_rcu() invocations | |
90 | use the current CPU's helper if there is one and the default | |
91 | helper otherwise. | |
92 | ||
93 | int set_cpu_call_rcu_data(int cpu, struct call_rcu_data *crdp); | |
94 | ||
95 | Sets the specified CPU's call_rcu() helper to the handle | |
96 | specified by "crdp". Again, "crdp" can be NULL to disassociate | |
97 | this CPU from its helper thread. Once a CPU has been | |
98 | disassociated from its helper, further call_rcu() invocations | |
99 | that would otherwise have used this CPU's helper will instead | |
100 | use the default helper. | |
101 | ||
102 | int create_all_cpu_call_rcu_data(unsigned long flags) | |
103 | ||
104 | Creates a separate call_rcu() helper thread for each CPU. | |
105 | After this primitive is invoked, the global default call_rcu() | |
106 | helper thread will not be called. | |
107 | ||
108 | The set_thread_call_rcu_data(), set_cpu_call_rcu_data(), and | |
109 | create_all_cpu_call_rcu_data() functions may be combined to set up | |
110 | pretty much any desired association between worker and call_rcu() | |
111 | helper threads. If a given executable calls only call_rcu(), | |
112 | then that executable will have only the single global default | |
113 | call_rcu() helper thread. This will suffice in most cases. | |
114 | ||
115 | void call_rcu_data_free(struct call_rcu_data *crdp) | |
116 | ||
117 | Terminates a call_rcu() helper thread and frees its associated | |
118 | data. The caller must have ensured that this thread is no longer | |
119 | in use, for example, by passing NULL to set_thread_call_rcu_data() | |
120 | and set_cpu_call_rcu_data() as required. |