Add description of work queues to the porting guide. Update comments

binfmt/libelf/libelf_load.c

@@ -264,7 +264,10 @@ int elf_load(FAR struct elf_loadinfo_s *loadinfo)
   elf_elfsize(loadinfo);
 
   /* Determine the heapsize to allocate.  heapsize is ignored if there is
-   * no address environment.
+   * no address environment because the heap is a shared resource in that
+   * case.  If there is no dynamic stack then heapsize must at least as big
+   * as the fixed stack size since the stack will be allocated from the heap
+   * in that case.
    */
 
 #if !defined(CONFIG_ARCH_ADDRENV)

binfmt/libnxflat/libnxflat_addrenv.c

@@ -108,7 +108,10 @@ int nxflat_addrenv_alloc(FAR struct nxflat_loadinfo_s *loadinfo, size_t envsize)
     }
 
 #ifdef CONFIG_ARCH_ADDRENV
-  /* Determine the heapsize to allocate */
+  /* Determine the heapsize to allocate. If there is no dynamic stack then
+   * heapsize must at least as big as the fixed stack size since the stack
+   * will be allocated from the heap in that case.
+   */
 
 #ifdef CONFIG_ARCH_STACK_DYNAMIC
   heapsize = ARCH_HEAP_SIZE;

include/nuttx/wqueue.h

@@ -63,10 +63,6 @@
  *   (which runs at the lowest of priority and may not be appropriate
  *   if memory reclamation is of high priority).  If CONFIG_SCHED_HPWORK
  *   is enabled, then the following options can also be used:
- * CONFIG_SCHED_HPWORK - Build the high priority work queue. To preserve
- *   legacy behavior, CONFIG_SCHED_HPWORK is assumed to be true in a flat
- *   build (CONFIG_SCHED_KERNEL=n) but must be defined in kernel mode
- *   in order to build the high priority work queue.
  * CONFIG_SCHED_HPWORKPRIORITY - The execution priority of the high-
  *   priority worker thread.  Default: 224
  * CONFIG_SCHED_HPWORKPERIOD - How often the worker thread checks for
@@ -338,7 +334,7 @@ int work_usrstart(void);
  *
  * Description:
  *   Queue work to be performed at a later time.  All queued work will be
- *   performed on the worker thread of of execution (not the caller's).
+ *   performed on the worker thread of execution (not the caller's).
  *
  *   The work structure is allocated by caller, but completely managed by
  *   the work queue logic.  The caller should never modify the contents of
@@ -412,6 +408,7 @@ int work_signal(int qid);
  *   Check if the work structure is available.
  *
  * Input parameters:
+ *   work - The work queue structure to check.
  *   None
  *
  * Returned Value:

libc/Kconfig

@@ -409,7 +409,7 @@ config LIB_USRWORKPRIORITY
 	int "User mode priority worker thread priority"
 	default 100
 	---help---
-		The execution priority of the lopwer priority worker thread.  Default: 192
+		The execution priority of the user-mode priority worker thread.  Default: 100
 
 config LIB_USRWORKPERIOD
 	int "User mode worker thread period"
@@ -425,7 +425,7 @@ config LIB_USRWORKSTACKSIZE
 		The stack size allocated for the lower priority worker thread.  Default: 2K.
 
 endif # LIB_USRWORK
-endif # BUILD_PROTECTED
+endif # BUILD_PROTECTED || BUILD_KERNEL
 
 config LIB_KBDCODEC
 	bool "Keyboard CODEC"

sched/Kconfig

@@ -855,7 +855,7 @@ config SCHED_HPWORKPRIORITY
 		The higher priority worker thread is intended to serve as the
 		"bottom" half for device drivers.  As a consequence it must run at
 		a very high, fixed priority.  Typically, it should be the highest
-		priority thread in your system.  Default: 192
+		priority thread in your system.  Default: 224
 
 		For lower priority, application oriented worker thread support,
 		please consider enabling the lower priority work queue.  The lower
@@ -903,14 +903,14 @@ config SCHED_LPNTHREADS
 	default 4 if FS_AIO
 	---help---
 		This options selects multiple, low-priority threads.  This is
-		essentially a "thread pool" that provides multi-threaded service
-		of the low-priority work thread.  This breaks the serialization
+		essentially a "thread pool" that provides multi-threaded servicing
+		of the low-priority work queue.  This breaks the serialization
 		of the "queue" (hence, it is no longer a queue at all).
 
 		This options is required to support, for example, I/O operations
 		that stall waiting for input.  If there is only a single thread,
 		then the entire low-priority queue processing stalls in such cases.
-		Such behvior must be support for asynchronous I/O, AIO (for example).
+		Such behavior is necessary to support asynchronous I/O, AIO (for example).
 
 config SCHED_LPWORKPRIORITY
 	int "Low priority worker thread priority"
@@ -959,7 +959,7 @@ config SCHED_LPWORKPRIOMAX
 		it must run at a very high, fixed priority.  Typically, it should
 		be the highest priority thread in your system.
 
-		This function provides an upper limit on the priority of the lower
+		This value provides an upper limit on the priority of the lower
 		priority worker thread.  This would be necessary, for example, if
 		the higher priority worker thread were to defer work to the lower
 		priority thread.  Clearly, in such a case, you would want to limit