1iv_work(3) ivykis programmer's manual iv_work(3)
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6 IV_WORK_POOL_INIT, iv_work_pool_create, iv_work_pool_put,
7 IV_WORK_ITEM_INIT, iv_work_pool_submit_work - ivykis worker thread man‐
8 agement
9
11 #include <iv_work.h>
12 struct iv_work_pool {
14 int max_threads;
15 void *cookie;
16 void (*thread_start)(void *cookie);
17 void (*thread_stop)(void *cookie);
18 };
19 struct iv_work_item {
21 void *cookie;
22 void (*work)(void *cookie);
23 void (*completion)(void *cookie);
24 };
25 void IV_WORK_POOL_INIT(struct iv_work_pool *this);
27 int iv_work_pool_create(struct iv_work_pool *this);
28 int iv_work_pool_put(struct iv_work_pool *this);
29 void IV_WORK_ITEM_INIT(struct iv_work_item *work);
30 int iv_work_pool_submit_work(struct iv_work_pool *this, struct
31 iv_work_item *work);
32
34 Calling iv_work_pool_create on a struct iv_work_pool object previously
35 initialised by IV_WORK_POOL_INIT creates a pool of worker threads that
36 can be used to offload CPU intensive tasks to, so as to prevent nega‐
37 tively influencing event handling latency in the calling thread, and to
38 enable the use of multiple host CPUs for CPU intensive tasks.
39 iv_work dynamically adjusts the number of threads in the pool to the
41 amount of work there is to do. The ->max_threads member of struct
42 iv_work_pool specifies the maximum number of threads that will be cre‐
43 ated in this pool.
44 Calling iv_work_pool_submit_work on a struct iv_work_item object previ‐
46 ously initialised by IV_WORK_ITEM_INIT submits a work item to a pool.
47 The ->work member of struct iv_work_item specifies the function that
48 will be called in one of the worker threads in the pool specified by
49 ->this, with ->cookie as its sole argument. When the work function has
50 completed, iv_work will call the ->completion callback to indicate
51 this, also with ->cookie as its sole argument, in the thread that
52 iv_work_pool_create was called in for this pool object.
53 As a special case, calling iv_work_pool_submit_work with a NULL work
55 pool pointer will cause the work item to be processed in the local
56 thread, from an iv_task(3) callback.
57 If the ->thread_start function pointer specified in struct iv_work_pool
59 is not NULL, it will be called upon creation of a new worker thread, in
60 the context of the created worker thread, with ->cookie as its sole
61 argument. Calls to ->thread_start are not explicitly serialised, which
62 should be kept in mind when manipulating state shared between threads
63 from within that callback function.
64 Similarly, if iv_work decides to terminate a worker thread, for example
66 due to inactivity, ->thread_stop will be called in the context of the
67 terminating thread, with ->cookie as its sole argument. Calls to
68 ->thread_stop are also not explicitly serialised.
69 iv_work_pool_submit_work can only be called from the thread that
71 iv_work_pool_create for this pool object was called in.
72 There is no way to cancel submitted work items.
74 There is no guaranteed order, FIFO or otherwise, between different work
76 items submitted to the same worker thread pool.
77 When the user has no more work items to submit to the pool, its refer‐
79 ence to the pool can be dropped by calling iv_work_pool_put.
80 If there are still pending or running work items assigned to this pool
82 when iv_work_pool_put is called, those work items will not be canceled,
83 but will be allowed to run to completion, and their ->completion call‐
84 backs will be called as usual. A similar thing holds for the
85 ->thread_start and ->thread_stop callbacks -- they can also still be
86 called after iv_work_pool_put returns. Even so, the memory correspond‐
87 ing to the struct iv_work_pool can immediately be freed or reused by
88 the user upon return of the iv_work_pool_put call.
89 Internally, iv_work uses iv_thread(3) for its thread management.
91
93 ivykis(3), iv_thread(3)
94ivykis 2010-09-14 iv_work(3)