For non-timeout tasks this priority behaves same way. Tasks are run
in FIFO (First-In-First-Out) order.
- SILC_TASK_PRI_HIGH
-
- High priority for important tasks. This priority should be used only
- for important tasks. Life is very fair for tasks with this priority.
- These tasks are run as soon as its timeout has expired. They are run
- before normal or lower tasks, respectively. For non-timeout tasks
- this priority behaves same way. Tasks are run in FIFO order.
-
- SILC_TASK_PRI_REALTIME
-
- Highest priority. This priority should be used very carefully because
- it can make the scheduler extremely unfair to other tasks. The task
- will be run as soon as its timeout has expired. The task is run before
- any other task. It is also quaranteed that the last registered task
- with this priority is the first task to be run when its timeout
- expires. Tasks are run in LIFO (Last-In-First-Out) order. To make
- scheduler fair there should never be more than one task in the queue
- with this priority. Currently none of the tasks in SILC are important
- enough to use this priority. For non-timeout tasks this priority
- behaves same way.
-
*/
typedef enum {
SILC_TASK_PRI_LOW,
SILC_TASK_PRI_NORMAL,
- SILC_TASK_PRI_HIGH,
- SILC_TASK_PRI_REALTIME,
} SilcTaskPriority;
/*
task queue this is not defined. This is meant only for internal
use and it should be considered to be read-only field.
- SilcTask (*register_task)(SilcTaskQueue, int,
- SilcTaskCallback, void *,
- long, long,
- SilcTaskType,
- SilcTaskPriority)
-
- Registers a new task to the task queue. Arguments are as follows:
-
- SilcTaskQueue queue Queue where the task is to be registered
- int fd File descriptor
- SilcTaskCallback cb Callback function to call
- void *context Context to be passed to callback function
- long seconds Seconds to timeout
- long useconds Microseconds to timeout
- SilcTaskType type Type of the task
- SilcTaskPriority priority Priority of the task
-
- The same function is used to register all types of tasks. The type
- argument tells what type of the task is. Note that when registering
- non-timeout tasks one should also pass 0 as timeout as timeout will
- be ignored anyway. Also, note, that one cannot register timeout task
- with 0 timeout. There cannot be zero timeouts, passing zero means
- no timeout is used for the task and SILC_TASK_FD_TASK is used as
- default task type in this case.
-
- One should be careful not to register timeout tasks to the non-timeout
- task queue, because they will never expire. As one should not register
- non-timeout tasks to timeout task queue because they will never get
- scheduled.
-
- There is a one distinct difference between timeout and non-timeout
- tasks when they are executed. Non-timeout tasks remain on the task
- queue after execution. Timeout tasks, however, are removed from the
- task queue after they have expired. It is safe to re-register a task
- in its own callback function. It is also safe to unregister a task
- in a callback function.
-
- Generic tasks apply to all file descriptors, however, one still must
- pass the correct file descriptor to the function when registering
- generic tasks.
-
- void (*unregister_task)(SilcTaskQueue, SilcTask)
-
- Unregisters a task already in the queue. Arguments are as follows:
-
- SilcTaskQueue queue Queue where from the task is unregistered
- SilcTask task Task to be unregistered
-
- The same function is used to unregister timeout and non-timeout
- tasks. One can also unregister all tasks from the queue by passing
- SILC_ALL_TASKS as task to the function. It is safe to unregister
- a task in a callback function.
-
- void (*set_iotype)(SilcTask, int type)
-
- Sets the I/O type of the task. The scheduler checks for this value
- and a task must always have at least one of the I/O types set at
- all time. When registering new task the type is set by default to
- SILC_TASK_READ. If the task doesn't perform reading one must reset
- the value to SILC_TASK_WRITE.
-
- The type sent as argumenet is masked into the task. If the tasks
- I/O mask already includes this type this function has no effect.
- Only one I/O type can be added at once. If the task must perform
- both reading and writing one must call this function for value
- SILC_TASK_WRITE as well.
-
- void (*reset_iotype)(SilcTask, int type)
-
- Resets the mask to the type sent as argument. Note that this resets
- the previous values to zero and then adds the type sent as argument.
- This function can be used to remove one of the types masked earlier
- to the task.
-
*/
typedef struct SilcTaskQueueStruct {
SilcTask task;
int valid;
struct timeval timeout;
-
- /* Method functions */
- SilcTask (*register_task)(struct SilcTaskQueueStruct *, int,
- SilcTaskCallback, void *, long, long,
- SilcTaskType, SilcTaskPriority);
- void (*unregister_task)(struct SilcTaskQueueStruct *, SilcTask);
- void (*set_iotype)(SilcTask, int type);
- void (*reset_iotype)(SilcTask, int type);
} SilcTaskQueueObject;
typedef SilcTaskQueueObject *SilcTaskQueue;
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