You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
149 lines
4.2 KiB
149 lines
4.2 KiB
/**
|
|
* xrdp: A Remote Desktop Protocol server.
|
|
*
|
|
* Copyright (C) Jay Sorg 2004-2012
|
|
*
|
|
* Licensed under the Apache License, Version 2.0 (the "License");
|
|
* you may not use this file except in compliance with the License.
|
|
* You may obtain a copy of the License at
|
|
*
|
|
* http://www.apache.org/licenses/LICENSE-2.0
|
|
*
|
|
* Unless required by applicable law or agreed to in writing, software
|
|
* distributed under the License is distributed on an "AS IS" BASIS,
|
|
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
|
|
* See the License for the specific language governing permissions and
|
|
* limitations under the License.
|
|
*
|
|
* session manager
|
|
* linux only
|
|
*/
|
|
|
|
#include "libscp_lock.h"
|
|
#include "thread_calls.h"
|
|
|
|
#include <pthread.h>
|
|
|
|
pthread_mutex_t lock_fork; /* this lock protects the counters */
|
|
pthread_mutexattr_t lock_fork_attr; /* mutex attributes */
|
|
tbus lock_fork_req; /* semaphore on which the process that are going to fork suspend on */
|
|
tbus lock_fork_wait; /* semaphore on which the suspended process wait on */
|
|
int lock_fork_forkers_count; /* threads that want to fork */
|
|
int lock_fork_blockers_count; /* threads thar are blocking fork */
|
|
int lock_fork_waiting_count; /* threads suspended until the fork finishes */
|
|
|
|
void DEFAULT_CC
|
|
scp_lock_init(void)
|
|
{
|
|
/* initializing fork lock */
|
|
pthread_mutexattr_init(&lock_fork_attr);
|
|
pthread_mutex_init(&lock_fork, &lock_fork_attr);
|
|
lock_fork_req = tc_sem_create(0);
|
|
lock_fork_wait = tc_sem_create(0);
|
|
|
|
/* here we don't use locking because lock_init() should be called BEFORE */
|
|
/* any thread is created */
|
|
lock_fork_blockers_count = 0;
|
|
lock_fork_waiting_count = 0;
|
|
lock_fork_forkers_count = 0;
|
|
}
|
|
|
|
/******************************************************************************/
|
|
void DEFAULT_CC
|
|
scp_lock_fork_request(void)
|
|
{
|
|
/* lock mutex */
|
|
pthread_mutex_lock(&lock_fork);
|
|
|
|
if (lock_fork_blockers_count == 0)
|
|
{
|
|
/* if no one is blocking fork(), then we're allowed to fork */
|
|
tc_sem_inc(lock_fork_req);
|
|
}
|
|
|
|
lock_fork_forkers_count++;
|
|
pthread_mutex_unlock(&lock_fork);
|
|
|
|
/* we wait to be allowed to fork() */
|
|
tc_sem_dec(lock_fork_req);
|
|
}
|
|
|
|
/******************************************************************************/
|
|
void DEFAULT_CC
|
|
scp_lock_fork_release(void)
|
|
{
|
|
pthread_mutex_lock(&lock_fork);
|
|
lock_fork_forkers_count--;
|
|
|
|
/* if there's someone else that want to fork, we let him fork() */
|
|
if (lock_fork_forkers_count > 0)
|
|
{
|
|
tc_sem_inc(lock_fork_req);
|
|
}
|
|
|
|
for (; lock_fork_waiting_count > 0; lock_fork_waiting_count--)
|
|
{
|
|
/* waking up the other processes */
|
|
tc_sem_inc(lock_fork_wait);
|
|
}
|
|
|
|
pthread_mutex_unlock(&lock_fork);
|
|
}
|
|
|
|
/******************************************************************************/
|
|
void DEFAULT_CC
|
|
scp_lock_fork_critical_section_end(int blocking)
|
|
{
|
|
//LOG_DBG("lock_fork_critical_section_end()",0);
|
|
/* lock mutex */
|
|
pthread_mutex_lock(&lock_fork);
|
|
|
|
if (blocking == LIBSCP_LOCK_FORK_BLOCKER)
|
|
{
|
|
lock_fork_blockers_count--;
|
|
}
|
|
|
|
/* if there's someone who wants to fork and we're the last blocking */
|
|
/* then we let him go */
|
|
if ((lock_fork_blockers_count == 0) && (lock_fork_forkers_count > 0))
|
|
{
|
|
tc_sem_inc(lock_fork_req);
|
|
}
|
|
|
|
pthread_mutex_unlock(&lock_fork);
|
|
}
|
|
|
|
/******************************************************************************/
|
|
int DEFAULT_CC
|
|
scp_lock_fork_critical_section_start(void)
|
|
{
|
|
//LOG_DBG("lock_fork_critical_section_start()",0);
|
|
do
|
|
{
|
|
pthread_mutex_lock(&lock_fork);
|
|
|
|
/* someone requested to fork */
|
|
if (lock_fork_forkers_count > 0)
|
|
{
|
|
lock_fork_waiting_count++;
|
|
pthread_mutex_unlock(&lock_fork);
|
|
|
|
/* we wait until the fork finishes */
|
|
tc_sem_dec(lock_fork_wait);
|
|
|
|
}
|
|
else
|
|
{
|
|
/* no fork, so we can go on... */
|
|
lock_fork_blockers_count++;
|
|
pthread_mutex_unlock(&lock_fork);
|
|
|
|
return LIBSCP_LOCK_FORK_BLOCKER;
|
|
}
|
|
}
|
|
while (1);
|
|
|
|
/* we'll never get here */
|
|
return LIBSCP_LOCK_FORK_WAITING;
|
|
}
|