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drivers/serial.c: Make sure that priority inheritance is not enabled for the signaling semaphores used in the serial driver.

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This commit is contained in:
Gregory Nutt 2016-11-03 08:16:59 -06:00
parent 54d7656f18
commit 47b043df1e
1 changed files with 17 additions and 21 deletions
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38
drivers/serial/serial.c
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@ -43,7 +43,6 @@
#include <stdint.h>
#include <stdbool.h>
#include <unistd.h>
#include <semaphore.h>
#include <string.h>
#include <fcntl.h>
#include <poll.h>
@ -52,6 +51,7 @@
#include <nuttx/irq.h>
#include <nuttx/arch.h>
#include <nuttx/semaphore.h>
#include <nuttx/fs/fs.h>
#include <nuttx/serial/serial.h>
#include <nuttx/fs/ioctl.h>
@ -112,16 +112,6 @@ static const struct file_operations g_serialops =
* Private Functions
************************************************************************************/
/************************************************************************************
* Name: sem_reinit
************************************************************************************/
static int sem_reinit(FAR sem_t *sem, int pshared, unsigned int value)
{
sem_destroy(sem);
return sem_init(sem, pshared, value);
}
/************************************************************************************
* Name: uart_takesem
************************************************************************************/
@ -1253,19 +1243,14 @@ static int uart_close(FAR struct file *filep)
/* We need to re-initialize the semaphores if this is the last close
* of the device, as the close might be caused by pthread_cancel() of
* a thread currently blocking on any of them.
*
* REVISIT: This logic *only* works in the case where the cancelled
* thread had the only reference to the serial driver. If there other
* references, then the this logic will not be executed and the
* semaphore count will still be incorrect.
*/
sem_reinit(&dev->xmitsem, 0, 0);
sem_reinit(&dev->recvsem, 0, 0);
sem_reinit(&dev->xmit.sem, 0, 1);
sem_reinit(&dev->recv.sem, 0, 1);
sem_reset(&dev->xmitsem, 0);
sem_reset(&dev->recvsem, 0);
sem_reset(&dev->xmit.sem, 1);
sem_reset(&dev->recv.sem, 1);
#ifndef CONFIG_DISABLE_POLL
sem_reinit(&dev->pollsem, 0, 1);
sem_reset(&dev->pollsem, 1);
#endif
uart_givesem(&dev->closesem);
@ -1416,6 +1401,8 @@ errout_with_sem:
int uart_register(FAR const char *path, FAR uart_dev_t *dev)
{
/* Initialize semaphores */
sem_init(&dev->xmit.sem, 0, 1);
sem_init(&dev->recv.sem, 0, 1);
sem_init(&dev->closesem, 0, 1);
@ -1425,6 +1412,15 @@ int uart_register(FAR const char *path, FAR uart_dev_t *dev)
sem_init(&dev->pollsem, 0, 1);
#endif
/* The recvsem and xmitsem are used for signaling and, hence, should not have
* priroity inheritance enabled.
*/
sem_setprotocol(&dev->xmitsem, SEM_PRIO_NONE);
sem_setprotocol(&dev->recvsem, SEM_PRIO_NONE);
/* Register the serial driver */
_info("Registering %s\n", path);
return register_driver(path, &g_serialops, 0666, dev);
}