Stackless-Python C-API

Stackless-Python provides the following C functions.

Tasklets

PyTaskletObject *PyTasklet_New(PyTypeObject *type, PyObject *func)

Return a new tasklet object. type must be derived from PyTasklet_Type or NULL. func must be a callable object or NULL or Py_None. If func is NULL or Py_None you must set it later with PyTasklet_BindEx().

int PyTasklet_Setup(PyTaskletObject *task, PyObject *args, PyObject *kwds)

Binds a tasklet function to parameters, making it ready to run and inserts in into the runnables queue. Returns 0 if successful or -1 in the case of failure.

int PyTasklet_BindEx(PyTaskletObject *task, PyObject *func, PyObject *args, PyObject *kwargs)

Binds a tasklet to a function and/or to parameters, making it ready to run. This is the C equivalent to method tasklet.bind(). The arguments func, args and kwargs are optional and may be NULL or Py_None. Returns 0 if successful or -1 in the case of failure.

int PyTasklet_BindThread(PyTaskletObject *task, long thread_id)

Binds a tasklet function to a thread. This is the C equivalent to method tasklet.bind_thread(). Returns 0 if successful or -1 in the case of failure.

int PyTasklet_Run(PyTaskletObject *task)

Forces task to run immediately. Returns 0 if successful, and -1 in the case of failure.

int PyTasklet_Run_nr(PyTaskletObject *task)

Forces task to run immediately, soft switching if possible. Returns 1 if the call soft switched, 0 if the call hard switched and -1 in the case of failure.

int PyTasklet_Switch(PyTaskletObject *task)

Forces task to run immediately. The previous tasklet is paused. Returns 0 if successful, and -1 in the case of failure.

int PyTasklet_Switch_nr(PyTaskletObject *task)

Forces task to run immediately, soft switching if possible. The previous tasklet is paused. Returns 1 if the call soft switched, 0 if the call hard switched and -1 in the case of failure.

int PyTasklet_Remove(PyTaskletObject *task)

Removes task from the runnables queue. Be careful! If this tasklet has a C stack attached, you need to either resume running it or kill it. Just dropping it might give an inconsistent system state. Returns 0 if successful, and -1 in the case of failure.

int PyTasklet_Insert(PyTaskletObject *task)

Insert task into the runnables queue, if it isn’t already there. If it is blocked or dead, the function returns -1 and a RuntimeError is raised.

int PyTasklet_RaiseException(PyTaskletObject *self, PyObject *klass, PyObject *args)

Raises an instance of the klass exception on the self tasklet. klass must be a subclass of Exception. Returns 1 if the call soft switched, 0 if the call hard switched and -1 in the case of failure.

Note

Raising TaskletExit on a tasklet can be done to silently kill it, see PyTasklet_Kill().

int PyTasklet_Throw(PyTaskletObject *self, int pending, PyObject *exc, PyObject *val, PyObject *tb)

Raises (exc, val, tb) on the self tasklet. This is the C equivalent to method tasklet.throw(). Returns 1 if the call soft switched, 0 if the call hard switched and -1 in the case of failure.

int PyTasklet_Kill(PyTaskletObject *self)

Raises TaskletExit on tasklet self. This should result in task being silently killed. (This exception is ignored by tasklet_end and does not invoke main as exception handler.) Returns 1 if the call soft switched, 0 if the call hard switched and -1 in the case of failure.

int PyTasklet_KillEx(PyTaskletObject *self, int pending)

Raises TaskletExit on tasklet self. This is the C equivalent to method tasklet.kill(). Returns 1 if the call soft switched, 0 if the call hard switched and -1 in the case of failure.

int PyTasklet_GetAtomic(PyTaskletObject *task)

Returns 1 if task is atomic, otherwise 0.

int PyTasklet_SetAtomic(PyTaskletObject *task, int flag)

Returns 1 if task is currently atomic, otherwise 0. Sets the atomic attribute to the logical value of flag.

int PyTasklet_GetIgnoreNesting(PyTaskletObject *task)

Returns 1 if task ignores its nesting level when choosing whether to auto-schedule it, otherwise 0.

int PyTasklet_SetIgnoreNesting(PyTaskletObject *task, int flag)

Returns the existing value of the ignore_nesting attribute for the tasklet task, setting it to the logical value of flag. If true, the tasklet may be auto-scheduled even if its nesting_level is > 0.

int PyTasklet_GetBlockTrap(PyTaskletObject *task)

Returns 1 if task is designated as not being allowed to be blocked on a channel, otherwise 0.

void PyTasklet_SetBlockTrap(PyTaskletObject *task, int value)

Returns 1 if task was already designated as not being allowed to be blocked on a channel, otherwise 0. This attribute is set to the logical value of value.

PyObject *PyTasklet_GetFrame(PyTaskletObject *task)

Return value: New reference.

Returns the current frame that task is executing in, or NULL

int PyTasklet_IsMain(PyTaskletObject *task)

Returns 1 if task is the main tasklet, otherwise 0.

int PyTasklet_IsCurrent(PyTaskletObject *task)

Returns 1 if task is the current tasklet, otherwise 0.

int PyTasklet_GetRecursionDepth(PyTaskletObject *task)

Return the current recursion depth of task.

int PyTasklet_GetNestingLevel(PyTaskletObject *task)

Return the current nesting level of task.

int PyTasklet_Alive(PyTaskletObject *task)

Returns 1 if task is alive (has an associated frame), otherwise 0 if it is dead.

int PyTasklet_Paused(PyTaskletObject *task)

Returns 1 if task is paused, otherwise 0. A tasklet is paused if it is alive, but not scheduled or blocked on a channel.

int PyTasklet_Scheduled(PyTaskletObject *task)

Returns 1 if task is scheduled, otherwise 0. In the context of this function a tasklet is considered to be scheduled if it is alive, and in the scheduler runnables list or blocked on a channel.

int PyTasklet_Restorable(PyTaskletObject *task)

Returns 1 if task can be fully unpickled, otherwise 0. A tasklet can be pickled whether it is fully restorable or not for the purposes of debugging and introspection. A tasklet that has been hard-switched cannot be fully pickled, for instance.

Channels

PyChannelObject* PyChannel_New(PyTypeObject *type)

Return a new channel object, or NULL in the case of failure. type must be derived from PyChannel_Type or be NULL, otherwise a TypeError is raised.

int PyChannel_Send(PyChannelObject *self, PyObject *arg)

Return value: New reference.

Send arg on the channel self. Returns 0 if the operation was successful, or -1 in the case of failure.

int PyChannel_Send_nr(PyChannelObject *self, PyObject *arg)

Return value: New reference.

Send arg on the channel self, soft switching if possible. Returns 1 if the call soft switched, 0 if the call hard switched and -1 in the case of failure.

PyObject *PyChannel_Receive(PyChannelObject *self)

Return value: New reference.

Receive on the channel self. Returns a Python® object if the operation was successful, or NULL in the case of failure.

PyObject *PyChannel_Receive_nr(PyChannelObject *self)

Return value: New reference.

Receive on the channel self, soft switching if possible. Returns a Python® object if the operation was successful, Py_UnwindToken if a soft switch occurred, or NULL in the case of failure.

int PyChannel_SendException(PyChannelObject *self, PyObject *klass, PyObject *value)

Returns 0 if successful or -1 in the case of failure. An instance of the exception type klass is raised on the first tasklet blocked on channel self.

int PyChannel_SendThrow(PyChannelObject *self, PyObject *exc, PyObject *val, PyObject *tb)

Returns 0 if successful or -1 in the case of failure. (exc, val, tb) is raised on the first tasklet blocked on channel self.

PyObject *PyChannel_GetQueue(PyChannelObject *self)

Return value: New reference.

Returns the first tasklet in the channel self’s queue, or NULL in the case the queue is empty.

void PyChannel_Close(PyChannelObject *self)

Marks the channel self as closing. No further tasklets can be blocked on the it from this point, unless it is later reopened.

void PyChannel_Open(PyChannelObject *self)

Reopens the channel self. This allows tasklets to once again send and receive on it, if those operations would otherwise block the given tasklet.

int PyChannel_GetClosing(PyChannelObject *self)

Returns 1 if the channel self is marked as closing, otherwise 0.

int PyChannel_GetClosed(PyChannelObject *self)

Returns 1 if the channel self is marked as closing and there are no tasklets blocked on it, otherwise 0.

int PyChannel_GetPreference(PyChannelObject *self)

Returns the current scheduling preference value of self. See channel.preference.

void PyChannel_SetPreference(PyChannelObject *self, int val)

Sets the current scheduling preference value of self. See channel.preference.

int PyChannel_GetScheduleAll(PyChannelObject *self)

Gets the schedule_all override flag for self. See channel.schedule_all.

void PyChannel_SetScheduleAll(PyChannelObject *self, int val)

Sets the schedule_all override flag for self. See channel.schedule_all.

int PyChannel_GetBalance(PyChannelObject *self)

Gets the balance for self. See channel.balance.

stackless module

PyObject *PyStackless_Schedule(PyObject *retval, int remove)

Return value: New reference.

Suspend the current tasklet and schedule the next one in the cyclic chain. if remove is nonzero, the current tasklet will be removed from the chain. retval = success NULL = failure

PyObject *PyStackless_Schedule_nr(PyObject *retval, int remove)

Return value: New reference.

retval = success NULL = failure retval == Py_UnwindToken: soft switched

int PyStackless_GetRunCount()

get the number of runnable tasks of the current thread, including the current one. -1 = failure

PyObject *PyStackless_GetCurrent()

Return value: New reference.

Get the currently running tasklet, that is, “yourself”.

long PyStackless_GetCurrentId()

Get a unique integer ID for the current tasklet

Threadsafe.

This is useful for benchmarking code that needs to get some sort of a stack identifier and must not worry about the GIL being present and so on.

Note

1. the “main” tasklet on each thread will have the same id, even if a proper tasklet has not been initialized.
2. IDs may get recycled for new tasklets.

PyObject *PyStackless_RunWatchdog(long timeout)

Return value: New reference.

Runs the scheduler until there are no tasklets remaining within it, or until one of the scheduled tasklets runs for timeout VM instructions without blocking. Returns None if the scheduler is empty, a tasklet object if that tasklet timed out, or NULL in the case of failure. If a timed out tasklet is returned, it should be killed or reinserted.

This function can only be called from the main tasklet. During the run, main is suspended, but will be invoked after the action. You will write your exception handler here, since every uncaught exception will be directed to main.

PyObject *PyStackless_RunWatchdogEx(long timeout, int flags)

Return value: New reference.

Wraps PyStackless_RunWatchdog(), but allows its behaviour to be customised by the value of flags which may contain any of the following bits:

Py_WATCHDOG_THREADBLOCK

Allows a thread to block if it runs out of tasklets. Ideally it will be awakened by other threads using channels which its blocked tasklets are waiting on.

Py_WATCHDOG_SOFT

Instead of interrupting a tasklet, we wait until the next tasklet scheduling moment to return. Always returns Py_None, as everything is in order.

Py_WATCHDOG_IGNORE_NESTING

Allows interrupts at all levels, effectively acting as though the ignore_nesting attribute were set on all tasklets.

Py_WATCHDOG_TIMEOUT

Interprets timeout as a fixed run time, rather than a per-tasklet run limit. The function will then attempt to interrupt execution once this many total opcodes have been executed since the call was made.

debugging and monitoring functions

int PyStackless_SetChannelCallback(PyObject *callable)

channel debugging. The callable will be called on every send or receive. Passing NULL removes the handler. Parameters of the callable: channel, tasklet, int sendflag, int willblock -1 = failure

int PyStackless_SetScheduleCallback(PyObject *callable)

scheduler monitoring. The callable will be called on every scheduling. Passing NULL removes the handler. Parameters of the callable: from, to When a tasklet dies, to is None. After death or when main starts up, from is None. -1 = failure

void PyStackless_SetScheduleFastcallback(slp_schedule_hook_func func)

Scheduler monitoring with a faster interface.

Interface functions

Most of the above functions can be called both from “inside” and “outside” stackless. “inside” means there should be a running (c)frame on top which acts as the “main tasklet”. The functions do a check whether the main tasklet exists, and wrap themselves if it is necessary. The following routines are used to support this, and you may use them as well if you need to make your specific functions always available.

PyObject *PyStackless_Call_Main(PyObject *func, PyObject *args, PyObject *kwds)

Return value: New reference.

Run any callable as the “main” Python® function. Returns a Python® object, or NULL in the case of failure.

PyObject *PyStackless_CallMethod_Main(PyObject *o, char *name, char *format, ...)

Return value: New reference.

Convenience: Run any method as the “main” Python® function. Wraps PyStackless_Call_Main.