Update TODO. Provide do-nothing stubs for mutex attribute interfaces if features not enabled. pthread_cond includes a signaling semaphore and should call sem_setprotocol.

TODO

@@ -216,7 +216,7 @@ o Task/Scheduler (sched/)
   Status:      Open
   Priority:    Medium-ish
 
-  Title:       ISSUES WITH PRIORITY INHERITANCE WHEN SEMAPHORE USED AS IPC
+  Title:       ISSUES WITH PRIORITY INHERITANCE WHEN SEMAPHORE/MUTX IS USED AS IPC
   Description: Semaphores have multiple uses.  The typical usage is where
                the semaphore is used as lock on one or more resources.  In
                this typical case, priority inheritance works perfectly:  The
@@ -264,6 +264,20 @@ o Task/Scheduler (sched/)
                The fix is to call sem_setprotocol(SEM_PRIO_NONE) immediately
                after the sem_init() call so that there will be no priority
                inheritance operations on this semaphore used for signalling.
+
+               NOTE also that in NuttX, pthread mutexes are build on top of
+               binary semaphores.  As a result, the above recommendation also
+               applies when pthread mutexes are used for inter-thread
+               signaling.  That is, a mutex that is used for signaling should
+               be initialize like this (simplified, no error checking here):
+
+                  pthread_mutexattr_t attr;
+                  pthread_mutex_t mutex;
+
+                  pthread_mutexattr_init(&attr);
+                  pthread_mutexattr_settype(&attr, PTHREAD_PRIO_NONE);
+                  pthread_mutex_init(&mutex, &attr);
+
   Status:      Open
   Priority:    High.  If you have priority inheritance enabled and you use
                semaphores for signalling events, then you *must* call

arch/sim/src/up_uartwait.c

@@ -39,7 +39,7 @@
 
 #include <semaphore.h>
 
-#include <nuttx/sermaphore.h>
+#include <nuttx/semaphore.h>
 
 #include "up_internal.h"
 

include/pthread.h

@@ -96,12 +96,10 @@
  *  An implementation is allowed to map this mutex to one of the other mutex types.
  */
 
-#ifdef CONFIG_MUTEX_TYPES
+#define PTHREAD_MUTEX_NORMAL          0
-#  define PTHREAD_MUTEX_NORMAL        0
+#define PTHREAD_MUTEX_ERRORCHECK      1
-#  define PTHREAD_MUTEX_ERRORCHECK    1
+#define PTHREAD_MUTEX_RECURSIVE       2
-#  define PTHREAD_MUTEX_RECURSIVE     2
+#define PTHREAD_MUTEX_DEFAULT         PTHREAD_MUTEX_NORMAL
-#  define PTHREAD_MUTEX_DEFAULT       PTHREAD_MUTEX_NORMAL
-#endif
 
 /* Valid ranges for the pthread stacksize attribute */
 
@@ -389,10 +387,12 @@ int pthread_mutexattr_getpshared(FAR const pthread_mutexattr_t *attr,
                                  FAR int *pshared);
 int pthread_mutexattr_setpshared(FAR pthread_mutexattr_t *attr,
                                  int pshared);
-#ifdef CONFIG_MUTEX_TYPES
 int pthread_mutexattr_gettype(const pthread_mutexattr_t *attr, int *type);
 int pthread_mutexattr_settype(pthread_mutexattr_t *attr, int type);
-#endif
+int pthread_mutexattr_getprotocol(FAR const pthread_mutexattr_t *attr,
+                                  FAR int *protocol);
+int pthread_mutexattr_setprotocol(FAR pthread_mutexattr_t *attr,
+                                  int protocol);
 
 /* The following routines create, delete, lock and unlock mutexes. */
 
@@ -403,15 +403,6 @@ int pthread_mutex_lock(FAR pthread_mutex_t *mutex);
 int pthread_mutex_trylock(FAR pthread_mutex_t *mutex);
 int pthread_mutex_unlock(FAR pthread_mutex_t *mutex);
 
-#ifdef CONFIG_PRIORITY_INHERITANCE
-/* Manage priority inheritance */
-
-int pthread_mutexattr_getprotocol(FAR const pthread_mutexattr_t *attr,
-                                  FAR int *protocol);
-int pthread_mutexattr_setprotocol(FAR pthread_mutexattr_t *attr,
-                                  int protocol);
-#endif
-
 /* Operations on condition variables */
 
 int pthread_condattr_init(FAR pthread_condattr_t *attr);

libc/pthread/Make.defs

@@ -35,27 +35,24 @@
 
 # Add the pthread C files to the build
 
-CSRCS += pthread_attr_init.c pthread_attr_destroy.c \
+CSRCS += pthread_attr_init.c pthread_attr_destroy.c
-		  pthread_attr_setschedpolicy.c pthread_attr_getschedpolicy.c \
+CSRCS += pthread_attr_setschedpolicy.c pthread_attr_getschedpolicy.c
-		  pthread_attr_setinheritsched.c pthread_attr_getinheritsched.c \
+CSRCS += pthread_attr_setinheritsched.c pthread_attr_getinheritsched.c
-		  pthread_attr_setstacksize.c pthread_attr_getstacksize.c \
+CSRCS += pthread_attr_setstacksize.c pthread_attr_getstacksize.c
-		  pthread_attr_setschedparam.c pthread_attr_getschedparam.c \
+CSRCS += pthread_attr_setschedparam.c pthread_attr_getschedparam.c
-		  pthread_barrierattr_init.c pthread_barrierattr_destroy.c \
+CSRCS += pthread_barrierattr_init.c pthread_barrierattr_destroy.c
-		  pthread_barrierattr_getpshared.c pthread_barrierattr_setpshared.c \
+CSRCS += pthread_barrierattr_getpshared.c pthread_barrierattr_setpshared.c
-		  pthread_condattr_init.c pthread_condattr_destroy.c \
+CSRCS += pthread_condattr_init.c pthread_condattr_destroy.c
-		  pthread_mutexattr_init.c pthread_mutexattr_destroy.c \
+CSRCS += pthread_mutexattr_init.c pthread_mutexattr_destroy.c
-		  pthread_mutexattr_getpshared.c pthread_mutexattr_setpshared.c
+CSRCS += pthread_mutexattr_getpshared.c pthread_mutexattr_setpshared.c
+CSRCS += pthread_mutexattr_setprotocol.c pthread_mutexattr_getprotocol.c
+CSRCS += pthread_mutexattr_settype.c pthread_mutexattr_gettype.c
 
 ifeq ($(CONFIG_SMP),y)
 CSRCS += pthread_attr_getaffinity.c pthread_attr_setaffinity.c
 endif
 
 ifeq ($(CONFIG_MUTEX_TYPES),y)
-CSRCS += pthread_mutexattr_settype.c pthread_mutexattr_gettype.c
-endif
-
-ifeq ($(CONFIG_PRIORITY_INHERITANCE),y)
-CSRCS += pthread_mutexattr_setprotocol.c pthread_mutexattr_getprotocol.c
 endif
 
 ifeq ($(CONFIG_BUILD_PROTECTED),y)

libc/pthread/pthread_mutexattr_getprotocol.c

@@ -68,6 +68,11 @@ int pthread_mutexattr_getprotocol(FAR const pthread_mutexattr_t *attr,
 {
   DEBUGASSERT(attr != NULL && protocol != NULL);
 
+#ifdef CONFIG_PRIORITY_INHERITANCE
   linfo("Returning %d\n", attr->proto);
   return attr->proto;
+#else
+  linfo("Returning %d\n", PTHREAD_PRIO_NONE);
+  return PTHREAD_PRIO_NONE;
+#endif
 }

libc/pthread/pthread_mutexattr_gettype.c

@@ -41,8 +41,6 @@
 #include <pthread.h>
 #include <errno.h>
 
-#ifdef CONFIG_MUTEX_TYPES
-
 /****************************************************************************
  * Public Functions
  ****************************************************************************/
@@ -67,13 +65,15 @@
 
 int pthread_mutexattr_gettype(const pthread_mutexattr_t *attr, int *type)
 {
-  if (attr && type)
+  if (attr != NULL && type != NULL)
     {
+#ifdef CONFIG_MUTEX_TYPES
       *type = attr->type;
+#else
+      *type = PTHREAD_MUTEX_NORMAL;
+#endif
       return 0;
     }
 
   return EINVAL;
 }
-
-#endif /* CONFIG_MUTEX_TYPES */

libc/pthread/pthread_mutexattr_setprotocol.c

@@ -69,6 +69,7 @@ int pthread_mutexattr_setprotocol(FAR pthread_mutexattr_t *attr,
   linfo("attr=0x%p protocol=%d\n", attr, protocol);
   DEBUGASSERT(attr != NULL);
 
+#ifdef CONFIG_PRIORITY_INHERITANCE
   if (protocol >= PTHREAD_PRIO_NONE && protocol <= PTHREAD_PRIO_PROTECT)
     {
       attr->proto = protocol;
@@ -76,4 +77,14 @@ int pthread_mutexattr_setprotocol(FAR pthread_mutexattr_t *attr,
     }
 
   return EINVAL;
+
+#else
+  if (protocol == PTHREAD_PRIO_NONE)
+    {
+      return OK;
+    }
+
+  return ENOSYS;
+#endif
+
 }

libc/pthread/pthread_mutexattr_settype.c

@@ -41,8 +41,6 @@
 #include <pthread.h>
 #include <errno.h>
 
-#ifdef CONFIG_MUTEX_TYPES
-
 /****************************************************************************
  * Public Functions
  ****************************************************************************/
@@ -69,10 +67,17 @@ int pthread_mutexattr_settype(pthread_mutexattr_t *attr, int type)
 {
   if (attr && type >= PTHREAD_MUTEX_NORMAL && type <= PTHREAD_MUTEX_RECURSIVE)
     {
+#ifdef CONFIG_MUTEX_TYPES
       attr->type = type;
+#else
+      if (type != PTHREAD_MUTEX_NORMAL)
+        {
+          return ENOSYS;
+        }
+#endif
+
       return OK;
     }
+
   return EINVAL;
 }
-
-#endif /* CONFIG_MUTEX_TYPES */

sched/pthread/pthread_condinit.c

@@ -1,7 +1,7 @@
 /****************************************************************************
  * sched/pthread/pthread_condinit.c
  *
- *   Copyright (C) 2007-2009 Gregory Nutt. All rights reserved.
+ *   Copyright (C) 2007-2009, 2016 Gregory Nutt. All rights reserved.
  *   Author: Gregory Nutt <gnutt@nuttx.org>
  *
  * Redistribution and use in source and binary forms, with or without
@@ -40,9 +40,12 @@
 #include <nuttx/config.h>
 
 #include <pthread.h>
+#include <semaphore.h>
 #include <debug.h>
 #include <errno.h>
 
+#include <nuttx/semaphore.h>
+
 #include "pthread/pthread.h"
 
 /****************************************************************************
@@ -71,23 +74,28 @@ int pthread_cond_init(FAR pthread_cond_t *cond, FAR const pthread_condattr_t *at
 
   sinfo("cond=0x%p attr=0x%p\n", cond, attr);
 
-  if (!cond)
+  if (cond == NULL)
     {
       ret = EINVAL;
     }
 
-  /* Initialize the semaphore contained in the condition structure
+  /* Initialize the semaphore contained in the condition structure with
-   * with initial count = 0
+   * initial count = 0
    */
 
   else if (sem_init((FAR sem_t *)&cond->sem, 0, 0) != OK)
     {
       ret = EINVAL;
     }
+  else
+    {
+      /* The contained semaphore is used for signaling and, hence, should
+       * not have priority inheritance enabled.
+       */
+
+      sem_setprotocol(&cond->sem, SEM_PRIO_NONE);
+    }
 
   sinfo("Returning %d\n", ret);
   return ret;
 }
-
-
-