zephyr/kernel/nanokernel/core/nanofiber.c

/* nanofiber.c - VxMicro nanokernel fiber support primitives */

/*
 * Copyright (c) 2010-2014 Wind River Systems, Inc.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * 1) Redistributions of source code must retain the above copyright notice,
 * this list of conditions and the following disclaimer.
 *
 * 2) Redistributions in binary form must reproduce the above copyright notice,
 * this list of conditions and the following disclaimer in the documentation
 * and/or other materials provided with the distribution.
 *
 * 3) Neither the name of Wind River Systems nor the names of its contributors
 * may be used to endorse or promote products derived from this software without
 * specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

/*
DESCRIPTION
This module provides various nanokernel fiber related primitives,
either in the form of an actual function or an alias to a function.
*/

#ifdef CONFIG_MICROKERNEL
#include <microkernel/k_struct.h>
#include <microkernel.h>
#endif

#include <nanok.h>
#include <toolchain.h>
#include <sections.h>

/*******************************************************************************
*
* _insert_ccs - add a context into the list of runnable contexts
*
* The list of runnable contexts is maintained via a single linked list
* in priority order.  Numerically lower priorities represent higher priority
* contexts.
*
* \NOMANUAL
*
* RETURNS: N/A
*/

void _insert_ccs(tCCS **queue, tCCS *ccs)
{
	tCCS *pQ;

	pQ = (tCCS *)queue;

	/*
	 * Scan the "queue" until end of list or until context with numerically
	 * higher priority is located.  A context will be placed at the end of
	 * the series of equal priority contexts.
	 */

	while (pQ->link && (ccs->prio >= pQ->link->prio)) {
		pQ = pQ->link;
	}

	/*
	 * Insert context.  A context will be placed at the end of equal
	 * priority
	 * contexts.
	 */

	ccs->link = pQ->link;
	pQ->link = ccs;
}

/*******************************************************************************
*
* context_self_get - return the currently executing context
*
* This routine returns a pointer to the context control block of the currently
* executing context.  It is cast to a nano_context_id_t for use publically.
*
* RETURNS: nano_context_id_t of the currently executing context.
*/

nano_context_id_t context_self_get(void)
{
	return _NanoKernel.current;
}

/*******************************************************************************
*
* context_type_get - return the type of the currently executing context
*
* This routine returns the type of context currently executing.
*
* RETURNS: nano_context_type_t of the currently executing context.
*/

nano_context_type_t context_type_get(void)
{
	if (_IS_IN_ISR())
		return NANO_CTX_ISR;

	if ((_NanoKernel.current->flags & TASK) == TASK)
		return NANO_CTX_TASK;

	return NANO_CTX_FIBER;
}

/*******************************************************************************
*
* _context_essential_check - is the specified context essential?
*
* This routine indicates if the specified context is an essential system
* context.  A NULL context pointer indicates that the current context is
* to be queried.
*
* RETURNS: Non-zero if specified context is essential, zero if it is not
*/

int _context_essential_check(tCCS *pCtx /* pointer to context */
					   )
{
	return ((pCtx == NULL) ? _NanoKernel.current : pCtx)->flags & ESSENTIAL;
}

/* currently the fiber and task implementations are identical */

FUNC_ALIAS(_fiber_start, fiber_fiber_start, void);
FUNC_ALIAS(_fiber_start, task_fiber_start, void);
FUNC_ALIAS(_fiber_start, fiber_start, void);

/*******************************************************************************
*
* _fiber_start - initialize and start a fiber context
*
* This routine initilizes and starts a fiber context; it can be called from
* either a fiber or a task context.  When this routine is called from a
* task, the newly created fiber will start executing immediately.
*
* INTERNAL
* Given that this routine is _not_ ISR-callable, the following code is used
* to differentiate between a task and fiber context:
*
*    if ((_NanoKernel.current->flags & TASK) == TASK)
*
* Given that the _fiber_start() primitive is not considered real-time
* performance critical, a runtime check to differentiate between a calling
* task or fiber is performed in order to conserve footprint.
*
* RETURNS: N/A
*/

void _fiber_start(char *pStack,
			       unsigned stackSize, /* stack size in bytes */
			       nano_fiber_entry_t pEntry,
			       int parameter1,
			       int parameter2,
			       unsigned priority,
			       unsigned options)
{
	tCCS *ccs;
	unsigned int imask;

#ifdef CONFIG_INIT_STACKS
	k_memset((char *)pStack, 0xaa, stackSize);
#endif

	ccs = _NewContext((char *)pStack,
			  stackSize,
			  (_ContextEntry)pEntry,
			  (void *)parameter1,
			  (void *)parameter2,
			  (void *)0,
			  priority,
			  options);

	/* _NewContext() has already set the flags depending on the 'options'
	 * and 'priority' parameters passed to it */

	/* lock interrupts to prevent corruption of the runnable context list */

	imask = irq_lock();

	/* insert thew newly crafted CCS into the fiber runnable context list */

	_insert_ccs((tCCS **)&_NanoKernel.fiber, ccs);

	/*
	 * Simply return to the caller if the current context is FIBER,
	 * otherwise swap into the newly created fiber context
	 */

	if ((_NanoKernel.current->flags & TASK) == TASK)
		_Swap(imask);
	else
		irq_unlock(imask);
}

/*******************************************************************************
*
* fiber_yield - yield the current context
*
* Invocation of this routine results in the current context yielding to
* another context of the same or higher priority.  If there doesn't exist
* any other contexts of the same or higher priority that are runnable, this
* routine will return immediately.
*
* This routine can only be called from a fiber context.
*
* RETURNS: N/A
*/

void fiber_yield(void)
{
	unsigned int imask = irq_lock_inline();

	if ((_NanoKernel.fiber != (tCCS *)NULL) &&
	    (_NanoKernel.current->prio >= _NanoKernel.fiber->prio)) {
		/*
		 * Reinsert current context into the list of runnable contexts,
		 * and
		 * then swap to the context at the head of the fiber list.
		 */

		_insert_ccs(&(_NanoKernel.fiber), _NanoKernel.current);
		_Swap(imask);
	} else
		irq_unlock_inline(imask);
}

/*******************************************************************************
*
* _nano_fiber_swap - pass control from the currently executing fiber
*
* This routine is used when a fiber voluntarily gives up control of the CPU.
*
* This routine can only be called from a fiber context.
*
* RETURNS: This function never returns
*/

FUNC_NORETURN void _nano_fiber_swap(void)
{
	unsigned int imask;

	/*
	 * Since the currently running fiber is not queued onto the runnable
	 * fiber list, simply performing a _Swap() shall initiate a context
	 * switch to the highest priority fiber, or the highest priority task
	 * if there are no runnable fibers.
	 */

	imask = irq_lock();
	_Swap(imask);

	/*
	 * Compiler can't know that _Swap() won't return and will issue a
	 * warning
	 * unless we explicitly tell it that control never gets this far.
	 */

	CODE_UNREACHABLE;
}

#ifndef CONFIG_ARCH_HAS_NANO_FIBER_ABORT
/*******************************************************************************
*
* fiber_abort - abort the currently executing fiber
*
* This routine is used to abort the currrently executing fiber. This can occur
* because:
* - the fiber has explicitly aborted itself (by calling this routine),
* - the fiber has implicitly aborted itself (by returning from its entry point),
* - the fiber has encountered a fatal exception.
*
* This routine can only be called from a fiber context.
*
* RETURNS: This function never returns
*/

FUNC_NORETURN void fiber_abort(void)
{
	/* Do normal context exit cleanup, then give up CPU control */

	_context_exit(_NanoKernel.current);
	_nano_fiber_swap();
}
#endif