Decouple the user-space work queue from the kernel space work queues

16 files changed, 202 insertions, 205 deletions

diff --git a/nuttx/configs/mikroe-stm32f4/kernel/up_userspace.c b/nuttx/configs/mikroe-stm32f4/kernel/up_userspace.c
index ed2f7d8a9..b70a4e80a 100644
--- a/nuttx/configs/mikroe-stm32f4/kernel/up_userspace.c
+++ b/nuttx/configs/mikroe-stm32f4/kernel/up_userspace.c
@@ -130,7 +130,7 @@ const struct userspace_s userspace __attribute__ ((section (".userspace"))) =
 
   /* User-space work queue support (declared in include/nuttx/wqueue.h) */
 
-#if defined(CONFIG_SCHED_WORKQUEUE) && defined(CONFIG_SCHED_USRWORK)
+#ifdef CONFIG_SCHED_USRWORK
   .work_usrstart    = work_usrstart,
 #endif
 };
diff --git a/nuttx/configs/open1788/kernel/up_userspace.c b/nuttx/configs/open1788/kernel/up_userspace.c
index 48413ec15..29864ae10 100644
--- a/nuttx/configs/open1788/kernel/up_userspace.c
+++ b/nuttx/configs/open1788/kernel/up_userspace.c
@@ -130,7 +130,7 @@ const struct userspace_s userspace __attribute__ ((section (".userspace"))) =
 
   /* User-space work queue support (declared in include/nuttx/wqueue.h) */
 
-#if defined(CONFIG_SCHED_WORKQUEUE) && defined(CONFIG_SCHED_USRWORK)
+#ifdef CONFIG_SCHED_USRWORK
   .work_usrstart    = work_usrstart,
 #endif
 };
diff --git a/nuttx/configs/sam3u-ek/kernel/up_userspace.c b/nuttx/configs/sam3u-ek/kernel/up_userspace.c
index 7a71c8ad1..c9e07a1b0 100644
--- a/nuttx/configs/sam3u-ek/kernel/up_userspace.c
+++ b/nuttx/configs/sam3u-ek/kernel/up_userspace.c
@@ -130,7 +130,7 @@ const struct userspace_s userspace __attribute__ ((section (".userspace"))) =
 
   /* User-space work queue support (declared in include/nuttx/wqueue.h) */
 
-#if defined(CONFIG_SCHED_WORKQUEUE) && defined(CONFIG_SCHED_USRWORK)
+#ifdef CONFIG_SCHED_USRWORK
   .work_usrstart    = work_usrstart,
 #endif
 };
diff --git a/nuttx/configs/stm3240g-eval/kernel/up_userspace.c b/nuttx/configs/stm3240g-eval/kernel/up_userspace.c
index 7947c99de..8a68a70e2 100644
--- a/nuttx/configs/stm3240g-eval/kernel/up_userspace.c
+++ b/nuttx/configs/stm3240g-eval/kernel/up_userspace.c
@@ -130,7 +130,7 @@ const struct userspace_s userspace __attribute__ ((section (".userspace"))) =
 
   /* User-space work queue support (declared in include/nuttx/wqueue.h) */
 
-#if defined(CONFIG_SCHED_WORKQUEUE) && defined(CONFIG_SCHED_USRWORK)
+#ifdef CONFIG_SCHED_USRWORK
   .work_usrstart    = work_usrstart,
 #endif
 };
diff --git a/nuttx/configs/stm32f4discovery/kernel/up_userspace.c b/nuttx/configs/stm32f4discovery/kernel/up_userspace.c
index 36065bdae..0c5d7548d 100644
--- a/nuttx/configs/stm32f4discovery/kernel/up_userspace.c
+++ b/nuttx/configs/stm32f4discovery/kernel/up_userspace.c
@@ -131,7 +131,7 @@ const struct userspace_s userspace __attribute__ ((section (".userspace"))) =
 
   /* User-space work queue support (declared in include/nuttx/wqueue.h) */
 
-#if defined(CONFIG_SCHED_WORKQUEUE) && defined(CONFIG_SCHED_USRWORK)
+#ifdef CONFIG_SCHED_USRWORK
   .work_usrstart    = work_usrstart,
 #endif
 };
diff --git a/nuttx/include/nuttx/userspace.h b/nuttx/include/nuttx/userspace.h
index a8286b797..ce47a90cd 100644
--- a/nuttx/include/nuttx/userspace.h
+++ b/nuttx/include/nuttx/userspace.h
@@ -149,7 +149,7 @@ struct userspace_s
 
   /* User-space work queue support */
 
-#if defined(CONFIG_SCHED_WORKQUEUE) && defined(CONFIG_SCHED_USRWORK)
+#ifdef CONFIG_SCHED_USRWORK
   int (*work_usrstart)(void);
 #endif
 };
diff --git a/nuttx/include/nuttx/wqueue.h b/nuttx/include/nuttx/wqueue.h
index 37c5b7b5d..e55bdd20b 100644
--- a/nuttx/include/nuttx/wqueue.h
+++ b/nuttx/include/nuttx/wqueue.h
@@ -51,7 +51,9 @@
  * Pre-processor Definitions
  ****************************************************************************/
 /* Configuration ************************************************************/
-/* CONFIG_SCHED_WORKQUEUE.  Create a dedicated "worker" thread to
+/* CONFIG_SCHED_WORKQUEUE.  Not selectable.  Set by the configuration system
+ *   if either CONFIG_SCHED_HPWORK or CONFIG_SCHED_LPWORK are selected.
+ * CONFIG_SCHED_HPWORK.  Create a dedicated "worker" thread to
  *   handle delayed processing from interrupt handlers.  This feature
  *   is required for some drivers but, if there are not complaints,
  *   can be safely disabled.  The worker thread also performs
@@ -59,7 +61,7 @@
  *   from interrupt handlers.  If the worker thread is disabled,
  *   then that clean will be performed by the IDLE thread instead
  *   (which runs at the lowest of priority and may not be appropriate
- *   if memory reclamation is of high priority).  If CONFIG_SCHED_WORKQUEUE
+ *   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
@@ -77,11 +79,10 @@
  * CONFIG_SIG_SIGWORK - The signal number that will be used to wake-up
  *   the worker thread.  Default: 17
  *
- * CONFIG_SCHED_LPWORK. If CONFIG_SCHED_WORKQUEUE is defined, then a single
- *   work queue is created by default.  If CONFIG_SCHED_LPWORK is also defined
- *   then an additional, lower-priority work queue will also be created.  This
- *   lower priority work queue is better suited for more extended processing
- *   (such as file system clean-up operations)
+ * CONFIG_SCHED_LPWORK. If CONFIG_SCHED_LPWORK is selected then a lower-
+ *   priority work queue will be created.  This lower priority work queue
+ *   is better suited for more extended processing (such as file system
+ *   clean-up operations)
  * CONFIG_SCHED_LPNTHREADS - The number of thread in the low-priority queue's
  *   thread pool.  Default: 1
  * CONFIG_SCHED_LPWORKPRIORITY - The minimum execution priority of the lower
@@ -119,10 +120,7 @@
 
 #    undef CONFIG_SCHED_HPWORK
 #    undef CONFIG_SCHED_LPWORK
-
-#    ifndef CONFIG_SCHED_USRWORK
-#      undef CONFIG_SCHED_WORKQUEUE
-#    endif
+#    undef CONFIG_SCHED_WORKQUEUE
 
   /* User-space worker threads are not built in a kernel build when we are
    * building the kernel-space libraries (but we still need to know that it
@@ -144,7 +142,7 @@
 #  undef CONFIG_SCHED_USRWORK
 #endif
 
-#ifdef CONFIG_SCHED_WORKQUEUE
+#if defined(CONFIG_SCHED_WORKQUEUE) || defined(CONFIG_SCHED_USRWORK)
 
 /* High priority, kernel work queue configuration ***************************/
 
@@ -471,5 +469,5 @@ void lpwork_restorepriority(uint8_t reqprio);
 #endif
 
 #endif /* __ASSEMBLY__ */
-#endif /* CONFIG_SCHED_WORKQUEUE */
+#endif /* CONFIG_SCHED_WORKQUEUE || CONFIG_SCHED_USRWORK */
 #endif /* __INCLUDE_NUTTX_WQUEUE_H */
diff --git a/nuttx/libc/Kconfig b/nuttx/libc/Kconfig
index 028c70cfa..8226793f7 100644
--- a/nuttx/libc/Kconfig
+++ b/nuttx/libc/Kconfig
@@ -393,174 +393,15 @@ endif # ARCH_OPTIMIZED_FUNCTIONS
 
 comment "Non-standard Library Support"
 
-config SCHED_WORKQUEUE
-	bool "Enable worker thread"
-	default n
-	depends on !DISABLE_SIGNALS
-	---help---
-		Create a dedicated "worker" thread to handle delayed processing from interrupt
-		handlers.  This feature is required for some drivers but, if there are no
-		complaints, can be safely disabled.  The worker thread also performs
-		garbage collection -- completing any delayed memory deallocations from
-		interrupt handlers.  If the worker thread is disabled, then that clean up will
-		be performed by the IDLE thread instead (which runs at the lowest of priority
-		and may not be appropriate if memory reclamation is of high priority).
-
-if SCHED_WORKQUEUE
-
-config SCHED_HPWORK
-	bool "High priority (kernel) worker thread"
-	default y
-	---help---
-		If SCHED_WORKQUEUE is defined, then a single, high priority work
-		queue is created by default.  This high priority worker thread is
-		intended to serve as the "bottom half" for driver interrupt
-		handling.
-
-if SCHED_HPWORK
-
-config SCHED_WORKPRIORITY
-	int "High priority worker thread priority"
-	default 224
-	---help---
-		The execution priority of the higher priority worker thread.
-
-		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
-
-		For lower priority, application oriented worker thread support,
-		please consider enabling the lower priority work queue.  The lower
-		priority work queue runs at a lower priority, of course, but has
-		the added advantage that it supports "priority inheritance" (if
-		PRIORITY_INHERITANCE is also selected):  The priority of the lower
-		priority worker thread can then be adjusted to match the highest
-		priority client.
-
-config SCHED_WORKPERIOD
-	int "High priority worker thread period"
-	default 100000 if SCHED_LPWORK
-	default 50000 if !SCHED_LPWORK
-	---help---
-		How often the worker thread checks for work in units of microseconds.
-		Default:  If the high priority worker thread is performing garbage
-		collection, then the default is 50*1000 (50 MS).  Otherwise, if the
-		lower priority worker thread is performing garbage collection, the
-		default is 100*1000.
-
-config SCHED_WORKSTACKSIZE
-	int "High priority worker thread stack size"
-	default 2048
-	---help---
-		The stack size allocated for the worker thread.  Default: 2K.
-
-endif # SCHED_HPWORK
-
-config SCHED_LPWORK
-	bool "Low priority (kernel) worker thread"
-	default n
-	---help---
-		If SCHED_WORKQUEUE is defined, then a single work queue is created by
-		default.  If SCHED_LPWORK is also defined then an additional, lower-
-		priority work queue will also be created.  This lower priority work
-		queue is better suited for more extended, application oriented
-		processing (such as file system clean-up operations or asynchronous
-		I/O)
-
-if SCHED_LPWORK
-
-config SCHED_LPNTHREADS
-	int "Number of low-priority worker threads"
-	default 1 if !FS_AIO
-	default 4 if FS_AIO
-	---help---
-		This options selectes 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
-		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).
-
-config SCHED_LPWORKPRIORITY
-	int "Low priority worker thread priority"
-	default 50
-	---help---
-		The minimum execution priority of the lower priority worker thread.
-
-		The lower priority worker thread is intended support application-
-		oriented functions.  The lower priority work queue runs at a lower
-		priority, of course, but has the added advantage that it supports
-		"priority inheritance" (if PRIORITY_INHERITANCE is also selected):
-		The priority of the lower priority worker thread can then be
-		adjusted to match the highest priority client.  Default: 50
-
-		NOTE: This priority inheritance feature is not automatic.  The
-		lower priority worker thread will always a fixed priority unless
-		you implement logic that calls lpwork_boostpriority() to raise the
-		priority of the lower priority worker thread (typically called
-		before scheduling the work) and then call the matching
-		lpwork_restorepriority() when the work is completed (typically
-		called within the work handler at the completion of the work).
-		Currently, only the NuttX asynchronous I/O logic uses this dynamic
-		prioritization feature.
-
-		The higher priority worker thread, on the other hand, 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.
-
-config SCHED_LPWORKPRIOMAX
-	int "Low priority worker thread maximum priority"
-	default 176
-	depends on PRIORITY_INHERITANCE
-	---help---
-		The maximum execution priority of the lower priority worker thread.
-
-		The lower priority worker thread is intended support application-
-		oriented functions.  The lower priority work queue runs at a lower
-		priority, of course, but has the added advantage that it supports
-		"priority inheritance" (if PRIORITY_INHERITANCE is also selected):
-		The priority of the lower priority worker thread can then be
-		adjusted to match the highest priority client.
-
-		The higher priority worker thread, on the other hand, 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.
-
-		This function 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
-		the maximum priority of the lower priority work thread.  Default:
-		176
-
-config SCHED_LPWORKPERIOD
-	int "Low priority worker thread period"
-	default 50000
-	---help---
-		How often the lower priority worker thread checks for work in units
-		of microseconds. Default: 50*1000 (50 MS).
-
-config SCHED_LPWORKSTACKSIZE
-	int "Low priority worker thread stack size"
-	default 2048
-	---help---
-		The stack size allocated for the lower priority worker thread.  Default: 2K.
-
-endif # SCHED_LPWORK
-
 if BUILD_PROTECTED || BUILD_KERNEL
 
 config SCHED_USRWORK
 	bool "User mode worker thread"
 	default n
+	depends on !DISABLE_SIGNALS
 	---help---
-		User space work queues can also be made available for deferred processing in the NuttX kernel build.
+		User space work queues can also be made available for deferred
+		processing in the NuttX kernel build.
 
 if SCHED_USRWORK
 
@@ -585,7 +426,6 @@ config SCHED_USRWORKSTACKSIZE
 
 endif # SCHED_USRWORK
 endif # BUILD_PROTECTED
-endif # SCHED_WORKQUEUE
 
 config LIB_KBDCODEC
 	bool "Keyboard CODEC"
diff --git a/nuttx/libc/wqueue/Make.defs b/nuttx/libc/wqueue/Make.defs
index 36a2ccc98..ae2d6d5f4 100644
--- a/nuttx/libc/wqueue/Make.defs
+++ b/nuttx/libc/wqueue/Make.defs
@@ -33,7 +33,7 @@
 #
 ############################################################################
 
-ifeq ($(CONFIG_SCHED_WORKQUEUE),y)
+ifeq ($(CONFIG_SCHED_USRWORK),y)
 
 # Add the work queue C files to the build
 
diff --git a/nuttx/libc/wqueue/work_cancel.c b/nuttx/libc/wqueue/work_cancel.c
index 322a85ae7..0db49f246 100644
--- a/nuttx/libc/wqueue/work_cancel.c
+++ b/nuttx/libc/wqueue/work_cancel.c
@@ -48,8 +48,7 @@
 
 #include "wqueue/wqueue.h"
 
-#if defined(CONFIG_SCHED_WORKQUEUE) && defined(CONFIG_SCHED_USRWORK) && \
-   !defined(__KERNEL__)
+#if defined(CONFIG_SCHED_USRWORK) && !defined(__KERNEL__)
 
 /****************************************************************************
  * Pre-processor Definitions
@@ -163,4 +162,4 @@ int work_cancel(int qid, FAR struct work_s *work)
     }
 }
 
-#endif /* CONFIG_SCHED_WORKQUEUE && CONFIG_SCHED_USRWORK && !__KERNEL__ */
+#endif /* CONFIG_SCHED_USRWORK && !__KERNEL__ */
diff --git a/nuttx/libc/wqueue/work_lock.c b/nuttx/libc/wqueue/work_lock.c
index 8c39a2bbb..59de461bc 100644
--- a/nuttx/libc/wqueue/work_lock.c
+++ b/nuttx/libc/wqueue/work_lock.c
@@ -46,8 +46,7 @@
 
 #include "wqueue/wqueue.h"
 
-#if defined(CONFIG_SCHED_WORKQUEUE) && defined(CONFIG_SCHED_USRWORK) && \
-   !defined(__KERNEL__)
+#if defined(CONFIG_SCHED_USRWORK) && !defined(__KERNEL__)
 
 /****************************************************************************
  * Pre-processor Definitions
@@ -136,4 +135,4 @@ void work_unlock(void)
 #endif
 }
 
-#endif /* CONFIG_SCHED_WORKQUEUE && CONFIG_SCHED_USRWORK && !__KERNEL__*/
+#endif /* CONFIG_SCHED_USRWORK && !__KERNEL__*/
diff --git a/nuttx/libc/wqueue/work_queue.c b/nuttx/libc/wqueue/work_queue.c
index 19e441178..78280baac 100644
--- a/nuttx/libc/wqueue/work_queue.c
+++ b/nuttx/libc/wqueue/work_queue.c
@@ -50,8 +50,7 @@
 
 #include "wqueue/wqueue.h"
 
-#if defined(CONFIG_SCHED_WORKQUEUE) && defined(CONFIG_SCHED_USRWORK) && \
-   !defined(__KERNEL__)
+#if defined(CONFIG_SCHED_USRWORK) && !defined(__KERNEL__)
 
 /****************************************************************************
  * Pre-processor Definitions
@@ -175,4 +174,4 @@ int work_queue(int qid, FAR struct work_s *work, worker_t worker,
     }
 }
 
-#endif /* CONFIG_SCHED_WORKQUEUE && CONFIG_SCHED_USRWORK && !__KERNEL__ */
+#endif /* CONFIG_SCHED_USRWORK && !__KERNEL__ */
diff --git a/nuttx/libc/wqueue/work_signal.c b/nuttx/libc/wqueue/work_signal.c
index 1ab861dfe..62a29e26c 100644
--- a/nuttx/libc/wqueue/work_signal.c
+++ b/nuttx/libc/wqueue/work_signal.c
@@ -46,7 +46,7 @@
 
 #include "wqueue/wqueue.h"
 
-#ifdef CONFIG_SCHED_WORKQUEUE
+#if defined(CONFIG_SCHED_USRWORK) && !defined(__KERNEL__)
 
 /****************************************************************************
  * Pre-processor Definitions
@@ -113,4 +113,3 @@ int work_signal(int qid)
 }
 
 #endif /* CONFIG_SCHED_USRWORK && !__KERNEL__ */
-#endif /* CONFIG_SCHED_WORKQUEUE */
diff --git a/nuttx/libc/wqueue/work_usrthread.c b/nuttx/libc/wqueue/work_usrthread.c
index 48ccf1f8b..fc41837cc 100644
--- a/nuttx/libc/wqueue/work_usrthread.c
+++ b/nuttx/libc/wqueue/work_usrthread.c
@@ -52,8 +52,7 @@
 
 #include "wqueue/wqueue.h"
 
-#if defined(CONFIG_SCHED_WORKQUEUE) && defined(CONFIG_SCHED_USRWORK) && \
-   !defined(__KERNEL__)
+#if defined(CONFIG_SCHED_USRWORK) && !defined(__KERNEL__)
 
 /****************************************************************************
  * Pre-processor Definitions
@@ -404,4 +403,4 @@ int work_usrstart(void)
 #endif
 }
 
-#endif /* CONFIG_SCHED_WORKQUEUE && CONFIG_SCHED_USRWORK && !__KERNEL__*/
+#endif /* CONFIG_SCHED_USRWORK && !__KERNEL__*/
diff --git a/nuttx/libc/wqueue/wqueue.h b/nuttx/libc/wqueue/wqueue.h
index 13bfacf0a..e40a7f037 100644
--- a/nuttx/libc/wqueue/wqueue.h
+++ b/nuttx/libc/wqueue/wqueue.h
@@ -47,7 +47,7 @@
 
 #include <nuttx/wqueue.h>
 
-#ifdef CONFIG_SCHED_WORKQUEUE
+#if defined(CONFIG_SCHED_USRWORK) && !defined(__KERNEL__)
 
 /****************************************************************************
  * Pre-processor Definitions
@@ -70,7 +70,6 @@ struct usr_wqueue_s
  * Public Data
  ****************************************************************************/
 
-#if defined(CONFIG_SCHED_USRWORK) && !defined(__KERNEL__)
 /* The state of the user mode work queue */
 
 extern struct usr_wqueue_s g_usrwork;
@@ -105,9 +104,7 @@ extern pthread_mutex_t g_usrmutex;
  *
  ****************************************************************************/
 
-#if defined(CONFIG_SCHED_USRWORK) && !defined(__KERNEL__)
 int work_lock(void);
-#endif
 
 /****************************************************************************
  * Name: work_unlock
@@ -123,9 +120,7 @@ int work_lock(void);
  *
  ****************************************************************************/
 
-#if defined(CONFIG_SCHED_USRWORK) && !defined(__KERNEL__)
 void work_unlock(void);
-#endif
 
-#endif /* CONFIG_SCHED_WORKQUEUE */
+#endif /* CONFIG_SCHED_USRWORK && !__KERNEL__*/
 #endif /* __LIBC_WQUEUE_WQUEUE_H */
diff --git a/nuttx/sched/Kconfig b/nuttx/sched/Kconfig
index 3b9f8d006..641002b46 100644
--- a/nuttx/sched/Kconfig
+++ b/nuttx/sched/Kconfig
@@ -786,7 +786,7 @@ config SIG_SIGCONDTIMEDOUT
 config SIG_SIGWORK
 	int "SIGWORK"
 	default 17
-	depends on SCHED_WORKQUEUE
+	depends on SCHED_WORKQUEUE || SCHED_USRWORK
 	---help---
 		SIGWORK is a non-standard signal used to wake up the internal NuttX
 		worker thread.  This setting specifies the signal number that will be
@@ -813,6 +813,175 @@ config MQ_MAXMSGSIZE
 
 endmenu # POSIX Message Queue Options
 
+menu "Work Queue Support"
+
+config SCHED_WORKQUEUE
+#	bool "Enable worker thread"
+	bool
+	default n
+	depends on !DISABLE_SIGNALS
+	---help---
+		Create dedicated "worker" threads to handle delayed or asynchronous
+		processing.
+
+config SCHED_HPWORK
+	bool "High priority (kernel) worker thread"
+	default y
+	depends on !DISABLE_SIGNALS
+	select SCHED_WORKQUEUE
+	---help---
+		Create a dedicated high-priority "worker" thread to handle delayed
+		processing from interrupt handlers.  This feature is required for
+		some drivers but, if there are no complaints, can be safely
+		disabled.  The high priority worker thread also performs garbage
+		collection -- completing any delayed memory deallocations from
+		interrupt handlers.  If the high-priority worker thread is disabled,
+		then that clean up will be performed either by (1) the low-priority
+		worker thread, if enabled, and if not (2) the IDLE thread instead
+		(which runs at the lowest of priority and may not be appropriate if
+		memory reclamation is of high priority)
+
+		For other, less-critical asynchronous or delayed process, the
+		low-priority worker thread is recommended.
+
+if SCHED_HPWORK
+
+config SCHED_WORKPRIORITY
+	int "High priority worker thread priority"
+	default 224
+	---help---
+		The execution priority of the higher priority worker thread.
+
+		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
+
+		For lower priority, application oriented worker thread support,
+		please consider enabling the lower priority work queue.  The lower
+		priority work queue runs at a lower priority, of course, but has
+		the added advantage that it supports "priority inheritance" (if
+		PRIORITY_INHERITANCE is also selected):  The priority of the lower
+		priority worker thread can then be adjusted to match the highest
+		priority client.
+
+config SCHED_WORKPERIOD
+	int "High priority worker thread period"
+	default 100000 if SCHED_LPWORK
+	default 50000 if !SCHED_LPWORK
+	---help---
+		How often the worker thread checks for work in units of microseconds.
+		Default:  If the high priority worker thread is performing garbage
+		collection, then the default is 50*1000 (50 MS).  Otherwise, if the
+		lower priority worker thread is performing garbage collection, the
+		default is 100*1000.
+
+config SCHED_WORKSTACKSIZE
+	int "High priority worker thread stack size"
+	default 2048
+	---help---
+		The stack size allocated for the worker thread.  Default: 2K.
+
+endif # SCHED_HPWORK
+
+config SCHED_LPWORK
+	bool "Low priority (kernel) worker thread"
+	default n
+	depends on !DISABLE_SIGNALS
+	select SCHED_WORKQUEUE
+	---help---
+		If SCHED_LPWORK is defined then a lower-priority work queue will
+		be created.  This lower priority work queue is better suited for
+		more extended, application oriented processing (such as file system
+		clean-up operations or asynchronous I/O)
+
+if SCHED_LPWORK
+
+config SCHED_LPNTHREADS
+	int "Number of low-priority worker threads"
+	default 1 if !FS_AIO
+	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
+		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).
+
+config SCHED_LPWORKPRIORITY
+	int "Low priority worker thread priority"
+	default 50
+	---help---
+		The minimum execution priority of the lower priority worker thread.
+
+		The lower priority worker thread is intended support application-
+		oriented functions.  The lower priority work queue runs at a lower
+		priority, of course, but has the added advantage that it supports
+		"priority inheritance" (if PRIORITY_INHERITANCE is also selected):
+		The priority of the lower priority worker thread can then be
+		adjusted to match the highest priority client.  Default: 50
+
+		NOTE: This priority inheritance feature is not automatic.  The
+		lower priority worker thread will always a fixed priority unless
+		you implement logic that calls lpwork_boostpriority() to raise the
+		priority of the lower priority worker thread (typically called
+		before scheduling the work) and then call the matching
+		lpwork_restorepriority() when the work is completed (typically
+		called within the work handler at the completion of the work).
+		Currently, only the NuttX asynchronous I/O logic uses this dynamic
+		prioritization feature.
+
+		The higher priority worker thread, on the other hand, 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.
+
+config SCHED_LPWORKPRIOMAX
+	int "Low priority worker thread maximum priority"
+	default 176
+	depends on PRIORITY_INHERITANCE
+	---help---
+		The maximum execution priority of the lower priority worker thread.
+
+		The lower priority worker thread is intended support application-
+		oriented functions.  The lower priority work queue runs at a lower
+		priority, of course, but has the added advantage that it supports
+		"priority inheritance" (if PRIORITY_INHERITANCE is also selected):
+		The priority of the lower priority worker thread can then be
+		adjusted to match the highest priority client.
+
+		The higher priority worker thread, on the other hand, 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.
+
+		This function 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
+		the maximum priority of the lower priority work thread.  Default:
+		176
+
+config SCHED_LPWORKPERIOD
+	int "Low priority worker thread period"
+	default 50000
+	---help---
+		How often the lower priority worker thread checks for work in units
+		of microseconds. Default: 50*1000 (50 MS).
+
+config SCHED_LPWORKSTACKSIZE
+	int "Low priority worker thread stack size"
+	default 2048
+	---help---
+		The stack size allocated for the lower priority worker thread.  Default: 2K.
+
+endif # SCHED_LPWORK
+endmenu # Work Queue Support
+
 menu "Stack and heap information"
 
 config IDLETHREAD_STACKSIZE