/*
* 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 <libadt/list.h>
#include <psthread.h>
#include <malloc.h>
#include <unistd.h>
#include <thread.h>
#include <stdio.h>
#include <libarch/faddr.h>
#include <futex.h>
#include <assert.h>
#include <async.h>
#ifndef PSTHREAD_INITIAL_STACK_PAGES_NO
#define PSTHREAD_INITIAL_STACK_PAGES_NO 1
#endif
static LIST_INITIALIZE(ready_list);
static LIST_INITIALIZE(serialized_list);
static LIST_INITIALIZE(manager_list);
static void psthread_main(void);
static atomic_t psthread_futex = FUTEX_INITIALIZER;
/** Count of real threads that are in async_serialized mode */
static int serialized_threads; /* Protected by async_futex */
/** Thread-local count of serialization. If >0, we must not preempt */
static __thread int serialization_count;
/** Counter of threads residing in async_manager */
static int threads_in_manager;
/** Setup psthread information into TCB structure */
psthread_data_t *psthread_setup(void)
{
psthread_data_t *pt;
tcb_t *tcb;
tcb = __make_tls();
if (!tcb)
return NULL;
if (!pt) {
__free_tls(tcb);
return NULL;
}
tcb->pst_data = pt;
pt->tcb = tcb;
return pt;
}
void psthread_teardown(psthread_data_t *pt)
{
__free_tls(pt->tcb);
}
/** Function that spans the whole life-cycle of a pseudo thread.
*
* Each pseudo thread begins execution in this function.
* Then the function implementing the pseudo thread logic is called.
* After its return, the return value is saved for a potentional
* joiner. If the joiner exists, it is woken up. The pseudo thread
* then switches to another pseudo thread, which cleans up after it.
*/
void psthread_main(void)
{
psthread_data_t *pt = __tcb_get()->pst_data;
pt->retval = pt->func(pt->arg);
/*
* If there is a joiner, wake it up and save our return value.
*/
if (pt->joiner) {
list_append(&pt->joiner->link, &ready_list);
pt->joiner->joinee_retval = pt->retval;
}
psthread_schedule_next_adv(PS_FROM_DEAD);
/* not reached */
}
/** Schedule next userspace pseudo thread.
*
* If calling with PS_TO_MANAGER parameter, the async_futex should be
* held.
*
* @param ctype One of PS_SLEEP, PS_PREEMPT, PS_TO_MANAGER,
* PS_FROM_MANAGER, PS_FROM_DEAD. The parameter describes
* the circumstances of the switch.
* @return Return 0 if there is no ready pseudo thread,
* return 1 otherwise.
*/
int psthread_schedule_next_adv(pschange_type ctype)
{
psthread_data_t *srcpt, *dstpt;
int retval = 0;
futex_down(&psthread_futex);
if (ctype == PS_PREEMPT && list_empty(&ready_list))
goto ret_0;
if (ctype == PS_SLEEP) {
if (list_empty(&ready_list) && list_empty(&serialized_list))
goto ret_0;
}
if (ctype == PS_FROM_MANAGER) {
if (list_empty(&ready_list) && list_empty(&serialized_list))
goto ret_0;
/*
* Do not preempt if there is not sufficient count of thread
* managers.
*/
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 (ctype == PS_TO_MANAGER || ctype == PS_FROM_DEAD) {
while (list_empty(&manager_list)) {
futex_up(&psthread_futex);
async_create_manager();
futex_down(&psthread_futex);
}
}
srcpt = __tcb_get()->pst_data;
if (ctype != PS_FROM_DEAD) {
/* Save current state */
if (!context_save(&srcpt->ctx)) {
if (serialization_count)
srcpt->flags &= ~PSTHREAD_SERIALIZED;
if (srcpt->clean_after_me) {
/*
* Cleanup after the dead pseudo thread from
* which we restored context here.
*/
free(srcpt
->clean_after_me
->stack
); psthread_teardown(srcpt->clean_after_me);
srcpt->clean_after_me = NULL;
}
return 1; /* futex_up already done here */
}
/* Save myself to the correct run list */
if (ctype == PS_PREEMPT)
list_append(&srcpt->link, &ready_list);
else if (ctype == PS_FROM_MANAGER) {
list_append(&srcpt->link, &manager_list);
threads_in_manager--;
} else {
/*
* If ctype == PS_TO_MANAGER, don't save ourselves to
* any list, we should already be somewhere, or we will
* be lost.
*
* The ctype == PS_SLEEP case is similar. The pseudo
* thread has an external refernce which can be used to
* wake it up once that time has come.
*/
}
}
/* Choose new thread to run */
if (ctype == PS_TO_MANAGER || ctype == PS_FROM_DEAD) {
dstpt = list_get_instance(manager_list.next, psthread_data_t,
link);
if (serialization_count && ctype == PS_TO_MANAGER) {
serialized_threads++;
srcpt->flags |= PSTHREAD_SERIALIZED;
}
threads_in_manager++;
if (ctype == PS_FROM_DEAD)
dstpt->clean_after_me = srcpt;
} else {
if (!list_empty(&serialized_list)) {
dstpt = list_get_instance(serialized_list.next,
psthread_data_t, link);
serialized_threads--;
} else {
dstpt = list_get_instance(ready_list.next,
psthread_data_t, link);
}
}
list_remove(&dstpt->link);
futex_up(&psthread_futex);
context_restore(&dstpt->ctx);
/* not reached */
ret_0:
futex_up(&psthread_futex);
return retval;
}
/** Wait for uspace pseudo thread to finish.
*
* Each pseudo thread can be only joined by one other pseudo thread. Moreover,
* the joiner must be from the same thread as the joinee.
*
* @param psthrid Pseudo thread to join.
*
* @return Value returned by the finished thread.
*/
int psthread_join(pstid_t psthrid)
{
psthread_data_t *pt;
psthread_data_t *cur;
/* Handle psthrid = Kernel address -> it is wait for call */
pt = (psthread_data_t *) psthrid;
/*
* The joiner is running so the joinee isn't.
*/
cur = __tcb_get()->pst_data;
pt->joiner = cur;
psthread_schedule_next_adv(PS_SLEEP);
/*
* The joinee fills in the return value.
*/
return cur->joinee_retval;
}
/** Create a userspace pseudo thread.
*
* @param func Pseudo thread function.
* @param arg Argument to pass to func.
*
* @return Return 0 on failure or TLS of the new pseudo thread.
*/
pstid_t psthread_create(int (*func)(void *), void *arg)
{
psthread_data_t *pt;
pt = psthread_setup();
if (!pt)
return 0;
pt
->stack
= (char *) malloc(PSTHREAD_INITIAL_STACK_PAGES_NO
* getpagesize());
if (!pt->stack) {
psthread_teardown(pt);
return 0;
}
pt->arg= arg;
pt->func = func;
pt->clean_after_me = NULL;
pt->joiner = NULL;
pt->joinee_retval = 0;
pt->retval = 0;
pt->flags = 0;
context_save(&pt->ctx);
context_set(&pt->ctx, FADDR(psthread_main), pt->stack,
PSTHREAD_INITIAL_STACK_PAGES_NO * getpagesize(), pt->tcb);
return (pstid_t) pt;
}
/** Add a thread to the ready list.
*
* @param psthrid Pinter to the pseudo thread structure of the
* pseudo thread to be added.
*/
void psthread_add_ready(pstid_t psthrid)
{
psthread_data_t *pt;
pt = (psthread_data_t *) psthrid;
futex_down(&psthread_futex);
if ((pt->flags & PSTHREAD_SERIALIZED))
list_append(&pt->link, &serialized_list);
else
list_append(&pt->link, &ready_list);
futex_up(&psthread_futex);
}
/** Add a pseudo thread to the manager list.
*
* @param psthrid Pinter to the pseudo thread structure of the
* pseudo thread to be added.
*/
void psthread_add_manager(pstid_t psthrid)
{
psthread_data_t *pt;
pt = (psthread_data_t *) psthrid;
futex_down(&psthread_futex);
list_append(&pt->link, &manager_list);
futex_up(&psthread_futex);
}
/** Remove one manager from manager list */
void psthread_remove_manager(void)
{
futex_down(&psthread_futex);
if (list_empty(&manager_list)) {
futex_up(&psthread_futex);
return;
}
list_remove(manager_list.next);
futex_up(&psthread_futex);
}
/** Return thread id of the currently running thread.
*
* @return Pseudo thread ID of the currently running pseudo thread.
*/
pstid_t psthread_get_id(void)
{
return (pstid_t) __tcb_get()->pst_data;
}
/** Disable preemption
*
* If the thread 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. Interrupt messages can still be preempted.
*/
void psthread_inc_sercount(void)
{
serialization_count++;
}
/** Restore the preemption counter to the previous state. */
void psthread_dec_sercount(void)
{
serialization_count--;
}
/** @}
*/