nuttx/libc/modlib/modlib_registry.c

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/****************************************************************************
* libc/modlib/modlib_registry.c
*
* Copyright (C) 2015, 2017 Gregory Nutt. All rights reserved.
* Author: Gregory Nutt <gnutt@nuttx.org>
*
* 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 NuttX 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 OWNER 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.
*
****************************************************************************/
/****************************************************************************
* Included Files
****************************************************************************/
#include <nuttx/config.h>
#include <string.h>
#include <semaphore.h>
#include <debug.h>
#include <errno.h>
#include <nuttx/module.h>
#include <nuttx/lib/modlib.h>
/****************************************************************************
* Pre-processor Definitions
****************************************************************************/
#define NO_HOLDER ((pid_t)-1)
/****************************************************************************
* Private Types
****************************************************************************/
struct mod_registrylock_s
{
sem_t lock; /* The actual registry lock */
pid_t holder; /* The PID of the current holder of the lock */
int16_t count; /* The number of nested calls to modlib_registry_lock */
};
/****************************************************************************
* Private Data
****************************************************************************/
static struct mod_registrylock_s g_modlock =
{
SEM_INITIALIZER(1), /* lock */
0, /* pid */
0 /* count */
};
static FAR struct module_s *g_mod_registry;
/****************************************************************************
* Public Functions
****************************************************************************/
/****************************************************************************
* Name: modlib_registry_lock
*
* Description:
* Get exclusive access to the module registry.
*
* Input Parameters:
* None
*
* Returned Value:
* None
*
****************************************************************************/
void modlib_registry_lock(void)
{
pid_t me;
/* Do we already hold the semaphore? */
me = getpid();
if (me == g_modlock.holder)
{
/* Yes... just increment the count */
g_modlock.count++;
DEBUGASSERT(g_modlock.count > 0);
}
/* Take the semaphore (perhaps waiting) */
else
{
while (sem_wait(&g_modlock.lock) != 0)
{
/* The only case that an error should occr here is if
* the wait was awakened by a signal.
*/
ASSERT(get_errno() == EINTR);
}
/* No we hold the semaphore */
g_modlock.holder = me;
g_modlock.count = 1;
}
}
/****************************************************************************
* Name: modlib_registry_unlock
*
* Description:
* Relinquish the lock on the module registry
*
* Input Parameters:
* None
*
* Returned Value:
* None
*
****************************************************************************/
void modlib_registry_unlock(void)
{
DEBUGASSERT(g_modlock.holder == getpid());
/* Is this our last count on the semaphore? */
if (g_modlock.count > 1)
{
/* No.. just decrement the count */
g_modlock.count--;
}
/* Yes.. then we can really release the semaphore */
else
{
g_modlock.holder = NO_HOLDER;
g_modlock.count = 0;
sem_post(&g_modlock.lock);
}
}
/****************************************************************************
* Name: modlib_registry_add
*
* Description:
* Add a new entry to the module registry.
*
* Input Parameters:
* modp - The module data structure to be registered.
*
* Returned Value:
* None
*
* Assumptions:
* The caller holds the lock on the module registry.
*
****************************************************************************/
void modlib_registry_add(FAR struct module_s *modp)
{
DEBUGASSERT(modp);
modp->flink = g_mod_registry;
g_mod_registry = modp;
}
/****************************************************************************
* Name: modlib_registry_del
*
* Description:
* Remove a module entry from the registry
*
* Input Parameters:
* modp - The registry entry to be removed.
*
* Returned Value:
* Zero (OK) is returned if the registry entry was deleted. Otherwise,
* a negated errno value is returned.
*
* Assumptions:
* The caller holds the lock on the module registry.
*
****************************************************************************/
int modlib_registry_del(FAR struct module_s *modp)
{
FAR struct module_s *prev;
FAR struct module_s *curr;
for (prev = NULL, curr = g_mod_registry;
curr != NULL && curr != modp;
prev = curr, curr = curr->flink);
if (curr == NULL)
{
serr("ERROR: Could not find module entry\n");
return -ENOENT;
}
if (prev == NULL)
{
g_mod_registry = modp->flink;
}
else
{
prev->flink = modp->flink;
}
modp->flink = NULL;
return OK;
}
/****************************************************************************
* Name: modlib_registry_find
*
* Description:
* Find an entry in the module registry using the name of the module.
*
* Input Parameters:
* modname - The name of the module to be found
*
* Returned Value:
* If the registry entry is found, a pointer to the module entry is
* returned. NULL is returned if the entry is not found.
*
* Assumptions:
* The caller holds the lock on the module registry.
*
****************************************************************************/
#ifdef HAVE_MODLIB_NAMES
FAR struct module_s *modlib_registry_find(FAR const char *modname)
{
FAR struct module_s *modp;
for (modp = g_mod_registry;
modp != NULL && strncmp(modp->modname, modname, MODLIB_NAMEMAX) != 0;
modp = modp->flink);
return modp;
}
#endif
/****************************************************************************
* Name: modlib_registry_verify
*
* Description:
* Verify that a module handle is valid by traversing the module list and
* assuring that the module still resides in the list. If it does not,
* the handle is probably a stale pointer.
*
* Input Parameters:
* modp - The registry entry to be verified.
*
* Returned Value:
* Returns OK is the module is valid; -ENOENT otherwise.
*
* Assumptions:
* The caller holds the lock on the module registry.
*
****************************************************************************/
int modlib_registry_verify(FAR struct module_s *modp)
{
FAR struct module_s *node;
for (node = g_mod_registry; node != NULL; node = node->flink)
{
if (node == modp)
{
return OK;
}
}
return -ENOENT;
}
/****************************************************************************
* Name: modlib_registry_foreach
*
* Description:
* Visit each module in the registry
*
* Input Parameters:
* callback - This callback function was be called for each entry in the
* registry.
* arg - This opaque argument will be passed to the callback function.
*
* Returned Value:
* This function normally returns zero (OK). If, however, any callback
* function returns a non-zero value, the traversal will be terminated and
* that non-zero value will be returned.
*
****************************************************************************/
int modlib_registry_foreach(mod_callback_t callback, FAR void *arg)
{
FAR struct module_s *modp;
int ret = OK;
/* Get exclusive access to the module registry */
modlib_registry_lock();
/* Visit each installed module */
for (modp = g_mod_registry; modp != NULL; modp = modp->flink)
{
/* Perform the callback */
ret = callback(modp, arg);
if (ret != 0)
{
break;
}
}
modlib_registry_unlock();
return ret;
}