sem_tickwait(): Add a new, non-standard function to perform timed semaphore waits. It is functionally equialent to the standard sem_timedwait(), but more efficient for use in higher performance device drivers. Requested by Max Nekyudov

ChangeLog

@@ -10776,4 +10776,7 @@
 	  Based comments from Anton D. Kachalov (2015-07-29).
 	* STM32 F4:  Add DMA support to the ADC driver for STM32 F4.  From
 	  Max Kriegler (2015-07-30).
+	* sem_tickwait():  Added this furnction for internaluse within the
+	  OS.  It is a non-standard but more efficient version of sem_timedwait()
+	  for use in higher performance device drviers (2015-08-01).
 

include/nuttx/semaphore.h

@@ -1,7 +1,7 @@
 /****************************************************************************
  * include/nuttx/semaphore.h
  *
- *   Copyright (C) 2014 Gregory Nutt. All rights reserved.
+ *   Copyright (C) 2014-2015 Gregory Nutt. All rights reserved.
  *   Author: Gregory Nutt <gnutt@nuttx.org>
  *
  * Redistribution and use in source and binary forms, with or without
@@ -51,7 +51,7 @@
  ****************************************************************************/
 
 /****************************************************************************
- * Public Data
+ * Public Type Definitions
  ****************************************************************************/
 
 #ifdef CONFIG_FS_NAMED_SEMAPHORES
@@ -64,7 +64,6 @@ struct nsem_inode_s
 
   FAR struct inode *ns_inode;       /* Containing inode */
   sem_t ns_sem;                     /* The semaphore */
-
 };
 #endif
 
@@ -86,6 +85,26 @@ extern "C"
  * Public Function Prototypes
  ****************************************************************************/
 
+/****************************************************************************
+ * Name: sem_tickwait
+ *
+ * Description:
+ *   This function is a lighter weight version of sem_timedwait().  It is
+ *   non-standard and intended only for use within the RTOS.
+ *
+ * Parameters:
+ *   sem     - Semaphore object
+ *   ticks   - Ticks to wait until the semaphore is posted.  If ticks is
+ *             zero, then this function is equivalent to sem_trywait().
+ *
+ * Return Value:
+ *   Zero (OK) is returned on success.  A negated errno value is returned on
+ *   failure.  -ETIMEDOUT is returned on the timeout condition.
+ *
+ ****************************************************************************/
+
+int sem_tickwait(FAR sem_t *sem, uint32_t ticks);
+
 #undef EXTERN
 #ifdef __cplusplus
 }

sched/semaphore/Make.defs

@@ -1,7 +1,7 @@
 ############################################################################
 # sched/semaphore/Make.defs
 #
-#   Copyright (C) 2014 Gregory Nutt. All rights reserved.
+#   Copyright (C) 2014-2015 Gregory Nutt. All rights reserved.
 #   Author: Gregory Nutt <gnutt@nuttx.org>
 #
 # Redistribution and use in source and binary forms, with or without
@@ -33,8 +33,9 @@
 #
 ############################################################################
 
-CSRCS += sem_destroy.c sem_wait.c sem_trywait.c sem_timedwait.c
+CSRCS += sem_destroy.c sem_wait.c sem_trywait.c sem_tickwait.c
-CSRCS += sem_post.c sem_recover.c sem_waitirq.c
+CSRCS += sem_timedwait.c sem_timeout.c sem_post.c sem_recover.c
+CSRCS += sem_waitirq.c
 
 ifeq ($(CONFIG_PRIORITY_INHERITANCE),y)
 CSRCS += sem_initialize.c sem_holder.c

sched/semaphore/sem_initialize.c

@@ -45,26 +45,6 @@
 
 #ifdef CONFIG_PRIORITY_INHERITANCE
 
-/****************************************************************************
- * Pre-processor Definitions
- ****************************************************************************/
-
-/****************************************************************************
- * Private Type Declarations
- ****************************************************************************/
-
-/****************************************************************************
- * Global Variables
- ****************************************************************************/
-
-/****************************************************************************
- * Private Variables
- ****************************************************************************/
-
-/****************************************************************************
- * Private Functions
- ****************************************************************************/
-
 /****************************************************************************
  * Public Functions
  ****************************************************************************/
@@ -83,6 +63,7 @@
  *   None
  *
  * Assumptions:
+ *   Called once during OS startup initialization
  *
  ****************************************************************************/
 

sched/semaphore/sem_timedwait.c

@@ -53,75 +53,6 @@
 #include "clock/clock.h"
 #include "semaphore/semaphore.h"
 
-/****************************************************************************
- * Pre-processor Definitions
- ****************************************************************************/
-
-/****************************************************************************
- * Private Type Declarations
- ****************************************************************************/
-
-/****************************************************************************
- * Global Variables
- ****************************************************************************/
-
-/****************************************************************************
- * Private Variables
- ****************************************************************************/
-
-/****************************************************************************
- * Private Functions
- ****************************************************************************/
-
-/****************************************************************************
- * Name: sem_timeout
- *
- * Description:
- *   This function is called if the timeout elapses before the message queue
- *   becomes non-empty.
- *
- * Parameters:
- *   argc  - the number of arguments (should be 1)
- *   pid   - the task ID of the task to wakeup
- *
- * Return Value:
- *   None
- *
- * Assumptions:
- *
- ****************************************************************************/
-
-static void sem_timeout(int argc, wdparm_t pid)
-{
-  FAR struct tcb_s *wtcb;
-  irqstate_t flags;
-
-  /* Disable interrupts to avoid race conditions */
-
-  flags = irqsave();
-
-  /* Get the TCB associated with this pid.  It is possible that
-   * task may no longer be active when this watchdog goes off.
-   */
-
-  wtcb = sched_gettcb((pid_t)pid);
-
-  /* It is also possible that an interrupt/context switch beat us to the
-   * punch and already changed the task's state.
-   */
-
-  if (wtcb && wtcb->task_state == TSTATE_WAIT_SEM)
-    {
-      /* Cancel the semaphore wait */
-
-      sem_waitirq(wtcb, ETIMEDOUT);
-    }
-
-  /* Interrupts may now be enabled. */
-
-  irqrestore(flags);
-}
-
 /****************************************************************************
  * Public Functions
  ****************************************************************************/
@@ -147,9 +78,8 @@ static void sem_timeout(int argc, wdparm_t pid)
  *   abstime - The absolute time to wait until a timeout is declared.
  *
  * Return Value:
- *   One success, the length of the selected message in bytes is
+ *   Zero (OK) is returned on success.  On failure, -1 (ERROR) is returned
- *   returned.  On failure, -1 (ERROR) is returned and the errno
+ *   and the errno is set appropriately:
- *   is set appropriately:
  *
  *   EINVAL    The sem argument does not refer to a valid semaphore.  Or the
  *             thread would have blocked, and the abstime parameter specified
@@ -213,10 +143,7 @@ int sem_timedwait(FAR sem_t *sem, FAR const struct timespec *abstime)
     {
       /* We got it! */
 
-      irqrestore(flags);
+      goto success_with_irqdisabled;
-      wd_delete(rtcb->waitdog);
-      rtcb->waitdog = NULL;
-      return OK;
     }
 
   /* We will have to wait for the semaphore.  Make sure that we were provided
@@ -226,7 +153,7 @@ int sem_timedwait(FAR sem_t *sem, FAR const struct timespec *abstime)
   if (abstime->tv_nsec < 0 || abstime->tv_nsec >= 1000000000)
     {
       errcode = EINVAL;
-      goto errout_disabled;
+      goto errout_with_irqdisabled;
     }
 
   /* Convert the timespec to clock ticks.  We must have interrupts
@@ -240,20 +167,20 @@ int sem_timedwait(FAR sem_t *sem, FAR const struct timespec *abstime)
   if (errcode == OK && ticks <= 0)
     {
       errcode = ETIMEDOUT;
-      goto errout_disabled;
+      goto errout_with_irqdisabled;
     }
 
   /* Handle any time-related errors */
 
   if (errcode != OK)
     {
-      goto errout_disabled;
+      goto errout_with_irqdisabled;
     }
 
   /* Start the watchdog */
 
   errcode = OK;
-  wd_start(rtcb->waitdog, ticks, (wdentry_t)sem_timeout, 1, getpid());
+  (void)wd_start(rtcb->waitdog, ticks, (wdentry_t)sem_timeout, 1, getpid());
 
   /* Now perform the blocking wait */
 
@@ -271,28 +198,17 @@ int sem_timedwait(FAR sem_t *sem, FAR const struct timespec *abstime)
 
   /* We can now restore interrupts and delete the watchdog */
 
+  /* Success exits */
+
+success_with_irqdisabled:
   irqrestore(flags);
   wd_delete(rtcb->waitdog);
   rtcb->waitdog = NULL;
+  return OK;
 
-  /* We are either returning success or an error detected by sem_wait()
+  /* Error exits */
-   * or the timeout detected by sem_timeout().  The 'errno' value has
-   * been set appropriately by sem_wait() or sem_timeout() in those
-   * cases.
-   */
 
-  if (ret < 0)
+errout_with_irqdisabled:
-    {
-      /* On failure, restore the errno value returned by sem_wait */
-
-      set_errno(errcode);
-    }
-
-  return ret;
-
-/* Error exits */
-
-errout_disabled:
   irqrestore(flags);
   wd_delete(rtcb->waitdog);
   rtcb->waitdog = NULL;

sched/semaphore/sem_waitirq.c

@@ -45,26 +45,6 @@
 
 #include "semaphore/semaphore.h"
 
-/****************************************************************************
- * Pre-processor Definitions
- ****************************************************************************/
-
-/****************************************************************************
- * Private Type Declarations
- ****************************************************************************/
-
-/****************************************************************************
- * Global Variables
- ****************************************************************************/
-
-/****************************************************************************
- * Private Variables
- ****************************************************************************/
-
-/****************************************************************************
- * Private Functions
- ****************************************************************************/
-
 /****************************************************************************
  * Public Functions
  ****************************************************************************/

sched/semaphore/semaphore.h

@@ -1,7 +1,7 @@
 /****************************************************************************
  * sched/semaphore/semaphore.h
  *
- *   Copyright (C) 2007, 2009-2014 Gregory Nutt. All rights reserved.
+ *   Copyright (C) 2007, 2009-2015 Gregory Nutt. All rights reserved.
  *   Author: Gregory Nutt <gnutt@nuttx.org>
  *
  * Redistribution and use in source and binary forms, with or without
@@ -81,8 +81,14 @@ void sem_initialize(void);
 #  define sem_initialize()
 #endif
 
+/* Wake up a thread that is waiting on semaphore */
+
 void sem_waitirq(FAR struct tcb_s *wtcb, int errcode);
 
+/* Handle semaphore timer expiration */
+
+void sem_timeout(int argc, wdparm_t pid);
+
 /* Recover semaphore resources with a task or thread is destroyed  */
 
 void sem_recover(FAR struct tcb_s *tcb);