iv_work(3) ivykis programmer's manual iv_work(3)NAME
IV_WORK_POOL_INIT, iv_work_pool_create, iv_work_pool_put,
IV_WORK_ITEM_INIT, iv_work_pool_submit_work - ivykis worker thread man‐
agement
SYNOPSIS
#include <iv_work.h>
struct iv_work_pool {
int max_threads;
void *cookie;
void (*thread_start)(void *cookie);
void (*thread_stop)(void *cookie);
};
struct iv_work_item {
void *cookie;
void (*work)(void *cookie);
void (*completion)(void *cookie);
};
void IV_WORK_POOL_INIT(struct iv_work_pool *this);
int iv_work_pool_create(struct iv_work_pool *this);
int iv_work_pool_put(struct iv_work_pool *this);
void IV_WORK_ITEM_INIT(struct iv_work_item *work);
int iv_work_pool_submit_work(struct iv_work_pool *this, struct
iv_work_item *work);
DESCRIPTION
Calling iv_work_pool_create on a struct iv_work_pool object previously
initialised by IV_WORK_POOL_INIT creates a pool of worker threads that
can be used to offload CPU intensive tasks to, so as to prevent nega‐
tively influencing event handling latency in the calling thread, and to
enable the use of multiple host CPUs for CPU intensive tasks.
iv_work dynamically adjusts the number of threads in the pool to the
amount of work there is to do. The ->max_threads member of struct
iv_work_pool specifies the maximum number of threads that will be cre‐
ated in this pool.
Calling iv_work_pool_submit_work on a struct iv_work_item object previ‐
ously initialised by IV_WORK_ITEM_INIT submits a work item to a pool.
The ->work member of struct iv_work_item specifies the function that
will be called in one of the worker threads in the pool specified by
->this, with ->cookie as its sole argument. When the work function has
completed, iv_work will call the ->completion callback to indicate
this, also with ->cookie as its sole argument, in the thread that
iv_work_pool_create was called in for this pool object.
As a special case, calling iv_work_pool_submit_work with a NULL work
pool pointer will cause the work item to be processed in the local
thread, from an iv_task(3) callback.
If the ->thread_start function pointer specified in struct iv_work_pool
is not NULL, it will be called upon creation of a new worker thread, in
the context of the created worker thread, with ->cookie as its sole
argument. Calls to ->thread_start are not explicitly serialised, which
should be kept in mind when manipulating state shared between threads
from within that callback function.
Similarly, if iv_work decides to terminate a worker thread, for example
due to inactivity, ->thread_stop will be called in the context of the
terminating thread, with ->cookie as its sole argument. Calls to
->thread_stop are also not explicitly serialised.
iv_work_pool_submit_work can only be called from the thread that
iv_work_pool_create for this pool object was called in.
There is no way to cancel submitted work items.
There is no guaranteed order, FIFO or otherwise, between different work
items submitted to the same worker thread pool.
When the user has no more work items to submit to the pool, its refer‐
ence to the pool can be dropped by calling iv_work_pool_put.
If there are still pending or running work items assigned to this pool
when iv_work_pool_put is called, those work items will not be canceled,
but will be allowed to run to completion, and their ->completion call‐
backs will be called as usual. A similar thing holds for the
->thread_start and ->thread_stop callbacks -- they can also still be
called after iv_work_pool_put returns. Even so, the memory correspond‐
ing to the struct iv_work_pool can immediately be freed or reused by
the user upon return of the iv_work_pool_put call.
Internally, iv_work uses iv_thread(3) for its thread management.
SEE ALSOivykis(3), iv_thread(3)ivykis 2010-09-14 iv_work(3)
