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Diffstat (limited to 'nuttx/net/netdev_sem.c')
-rw-r--r-- | nuttx/net/netdev_sem.c | 178 |
1 files changed, 178 insertions, 0 deletions
diff --git a/nuttx/net/netdev_sem.c b/nuttx/net/netdev_sem.c new file mode 100644 index 000000000..ba6299c62 --- /dev/null +++ b/nuttx/net/netdev_sem.c @@ -0,0 +1,178 @@ +/**************************************************************************** + * net/netdev_sem.c + * + * Copyright (C) 2012 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> + +#if defined(CONFIG_NET) && CONFIG_NSOCKET_DESCRIPTORS > 0 + +#include <sys/types.h> + +#include <unistd.h> +#include <semaphore.h> +#include <assert.h> +#include <errno.h> + +#include "net_internal.h" + +/**************************************************************************** + * Definitions + ****************************************************************************/ + +#define NO_HOLDER (pid_t)-1 + +/**************************************************************************** + * Priviate Types + ****************************************************************************/ + +/* There is at least on context in which recursive semaphores are required: + * When netdev_foreach is used with a telnet client, we will deadlock if we + * do not provide this capability. + */ + +struct netdev_sem_s +{ + sem_t sem; + pid_t holder; + unsigned int count; +}; + +/**************************************************************************** + * Private Data + ****************************************************************************/ + +/**************************************************************************** + * Public Data + ****************************************************************************/ + +static struct netdev_sem_s g_devlock; + +/**************************************************************************** + * Private Functions + ****************************************************************************/ + +/**************************************************************************** + * Global Functions + ****************************************************************************/ + +/**************************************************************************** + * Function: netdev_seminit + * + * Description: + * Initialize the network device semaphore. + * + ****************************************************************************/ + +void netdev_seminit(void) +{ + sem_init(&g_devlock.sem, 0, 1); + g_devlock.holder = NO_HOLDER; + g_devlock.count = 0; +} + +/**************************************************************************** + * Function: netdev_semtake + * + * Description: + * Get exclusive access to the network device list. + * + ****************************************************************************/ + +void netdev_semtake(void) +{ + pid_t me = getpid(); + + /* Does this thread already hold the semaphore? */ + + if (g_devlock.holder == me) + { + /* Yes.. just increment the reference count */ + + g_devlock.count++; + } + else + { + /* No.. take the semaphore (perhaps waiting) */ + + while (uip_lockedwait(&g_devlock.sem) != 0) + { + /* The only case that an error should occur here is if + * the wait was awakened by a signal. + */ + + ASSERT(errno == EINTR); + } + + /* Now this thread holds the semaphore */ + + g_devlock.holder = me; + g_devlock.count = 1; + } +} + +/**************************************************************************** + * Function: netdev_semtake + * + * Description: + * Release exclusive access to the network device list + * + ****************************************************************************/ + +void netdev_semgive(void) +{ + DEBUGASSERT(g_devlock.holder == getpid() && g_devlock.count > 0); + + /* If the count would go to zero, then release the semaphore */ + + if (g_devlock.count == 1) + { + /* We no longer hold the semaphore */ + + g_devlock.holder = NO_HOLDER; + g_devlock.count = 0; + sem_post(&g_devlock.sem); + } + else + { + /* We still hold the semaphore. Just decrement the count */ + + g_devlock.count--; + } +} + +#endif /* CONFIG_NET && CONFIG_NSOCKET_DESCRIPTORS */ |