/*
* Copyright (c) 2006 Ondrej Palkovsky
* Copyright (c) 2007 Jakub Jermar
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* - Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* - 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.
* - The name of the author may not be used to endorse or promote products
* derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``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 AUTHOR 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.
*/
/** @addtogroup libc
* @{
*/
/** @file
*/
#include <adt/list.h>
#include <fibril.h>
#include <thread.h>
#include <tls.h>
#include <malloc.h>
#include <unistd.h>
#include <stdio.h>
#include <libarch/faddr.h>
#include <futex.h>
#include <assert.h>
#include <async.h>
#ifndef FIBRIL_INITIAL_STACK_PAGES_NO
#define FIBRIL_INITIAL_STACK_PAGES_NO 1
#endif
/**
* This futex serializes access to ready_list, serialized_list and manager_list.
*/
static atomic_t fibril_futex = FUTEX_INITIALIZER;
static LIST_INITIALIZE(ready_list);
static LIST_INITIALIZE(serialized_list);
static LIST_INITIALIZE(manager_list);
static void fibril_main(void);
/** Number of threads that are executing a manager fibril. */
static int threads_in_manager;
/** Number of threads that are executing a manager fibril and are serialized. */
static int serialized_threads; /* Protected by async_futex */
/** Fibril-local count of serialization. If > 0, we must not preempt */
static fibril_local int serialization_count;
/** Setup fibril information into TCB structure */
fibril_t *fibril_setup(void)
{
fibril_t *f;
tcb_t *tcb;
tcb = __make_tls();
if (!tcb)
return NULL;
if (!f) {
__free_tls(tcb);
return NULL;
}
tcb->fibril_data = f;
f->tcb = tcb;
f->func = NULL;
f->arg = NULL;
f->stack = NULL;
f->clean_after_me = NULL;
f->retval = 0;
f->flags = 0;
return f;
}
void fibril_teardown(fibril_t *f)
{
__free_tls(f->tcb);
}
/** Function that spans the whole life-cycle of a fibril.
*
* Each fibril begins execution in this function. Then the function implementing
* the fibril logic is called. After its return, the return value is saved.
* The fibril then switches to another fibril, which cleans up after it.
*/
void fibril_main(void)
{
fibril_t *f = __tcb_get()->fibril_data;
/* Call the implementing function. */
f->retval = f->func(f->arg);
fibril_switch(FIBRIL_FROM_DEAD);
/* not reached */
}
/** Switch from the current fibril.
*
* If calling with FIBRIL_TO_MANAGER parameter, the async_futex should be
* held.
*
* @param stype Switch type. One of FIBRIL_PREEMPT, FIBRIL_TO_MANAGER,
* FIBRIL_FROM_MANAGER, FIBRIL_FROM_DEAD. The parameter
* describes the circumstances of the switch.
* @return Return 0 if there is no ready fibril,
* return 1 otherwise.
*/
int fibril_switch(fibril_switch_type_t stype)
{
fibril_t *srcf, *dstf;
int retval = 0;
futex_down(&fibril_futex);
if (stype == FIBRIL_PREEMPT && list_empty(&ready_list))
goto ret_0;
if (stype == FIBRIL_FROM_MANAGER) {
if (list_empty(&ready_list) && list_empty(&serialized_list))
goto ret_0;
/*
* Do not preempt if there is not enough threads to run the
* ready fibrils which are not serialized.
*/
if (list_empty(&serialized_list) &&
threads_in_manager <= serialized_threads) {
goto ret_0;
}
}
/* If we are going to manager and none exists, create it */
if (stype == FIBRIL_TO_MANAGER || stype == FIBRIL_FROM_DEAD) {
while (list_empty(&manager_list)) {
futex_up(&fibril_futex);
async_create_manager();
futex_down(&fibril_futex);
}
}
srcf = __tcb_get()->fibril_data;
if (stype != FIBRIL_FROM_DEAD) {
/* Save current state */
if (!context_save(&srcf->ctx)) {
/*
* Make sure to reload srcf with the current fibril
* address. Its value may be invalid after
* contex_restore() due to e.g. register recycling.
*/
srcf = __tcb_get()->fibril_data;
if (serialization_count)
srcf->flags &= ~FIBRIL_SERIALIZED;
if (srcf->clean_after_me) {
/*
* Cleanup after the dead fibril from which we
* restored context here.
*/
void *stack = srcf->clean_after_me->stack;
if (stack) {
/*
* This check is necessary because a
* thread could have exited like a
* normal fibril using the
* FIBRIL_FROM_DEAD switch type. In that
* case, its fibril will not have the
* stack member filled.
*/
}
fibril_teardown(srcf->clean_after_me);
srcf->clean_after_me = NULL;
}
return 1; /* futex_up already done here */
}
/* Save myself to the correct run list */
if (stype == FIBRIL_PREEMPT)
list_append(&srcf->link, &ready_list);
else if (stype == FIBRIL_FROM_MANAGER) {
list_append(&srcf->link, &manager_list);
threads_in_manager--;
} else {
/*
* If stype == FIBRIL_TO_MANAGER, don't put ourselves to
* any list, we should already be somewhere, or we will
* be lost.
*/
}
}
/* Choose a new fibril to run */
if (stype == FIBRIL_TO_MANAGER || stype == FIBRIL_FROM_DEAD) {
dstf = list_get_instance(manager_list.next, fibril_t, link);
if (serialization_count && stype == FIBRIL_TO_MANAGER) {
serialized_threads++;
srcf->flags |= FIBRIL_SERIALIZED;
}
threads_in_manager++;
if (stype == FIBRIL_FROM_DEAD)
dstf->clean_after_me = srcf;
} else {
if (!list_empty(&serialized_list)) {
dstf = list_get_instance(serialized_list.next, fibril_t,
link);
serialized_threads--;
} else {
dstf = list_get_instance(ready_list.next, fibril_t,
link);
}
}
list_remove(&dstf->link);
futex_up(&fibril_futex);
context_restore(&dstf->ctx);
/* not reached */
ret_0:
futex_up(&fibril_futex);
return retval;
}
/** Create a new fibril.
*
* @param func Implementing function of the new fibril.
* @param arg Argument to pass to func.
*
* @return Return 0 on failure or TLS of the new fibril.
*/
fid_t fibril_create(int (*func)(void *), void *arg)
{
fibril_t *f;
f = fibril_setup();
if (!f)
return 0;
f
->stack
= (char *) malloc(FIBRIL_INITIAL_STACK_PAGES_NO
* getpagesize());
if (!f->stack) {
fibril_teardown(f);
return 0;
}
f->func = func;
f->arg = arg;
context_save(&f->ctx);
context_set(&f->ctx, FADDR(fibril_main), f->stack,
FIBRIL_INITIAL_STACK_PAGES_NO * getpagesize(), f->tcb);
return (fid_t) f;
}
/** Add a fibril to the ready list.
*
* @param fid Pointer to the fibril structure of the fibril to be
* added.
*/
void fibril_add_ready(fid_t fid)
{
fibril_t *f;
f = (fibril_t *) fid;
futex_down(&fibril_futex);
if ((f->flags & FIBRIL_SERIALIZED))
list_append(&f->link, &serialized_list);
else
list_append(&f->link, &ready_list);
futex_up(&fibril_futex);
}
/** Add a fibril to the manager list.
*
* @param fid Pointer to the fibril structure of the fibril to be
* added.
*/
void fibril_add_manager(fid_t fid)
{
fibril_t *f;
f = (fibril_t *) fid;
futex_down(&fibril_futex);
list_append(&f->link, &manager_list);
futex_up(&fibril_futex);
}
/** Remove one manager from the manager list. */
void fibril_remove_manager(void)
{
futex_down(&fibril_futex);
if (list_empty(&manager_list)) {
futex_up(&fibril_futex);
return;
}
list_remove(manager_list.next);
futex_up(&fibril_futex);
}
/** Return fibril id of the currently running fibril.
*
* @return fibril ID of the currently running fibril.
*
*/
fid_t fibril_get_id(void)
{
return (fid_t) __tcb_get()->fibril_data;
}
/** Disable preemption
*
* If the fibril wants to send several message in a row and does not want to be
* preempted, it should start async_serialize_start() in the beginning of
* communication and async_serialize_end() in the end. If it is a true
* multithreaded application, it should protect the communication channel by a
* futex as well.
*
*/
void fibril_inc_sercount(void)
{
serialization_count++;
}
/** Restore the preemption counter to the previous state. */
void fibril_dec_sercount(void)
{
serialization_count--;
}
/** @}
*/