kernel: sched: impl sys workq item no block enforcement

The system workqueue should never be unreadied from a work item
handler (while busy). This commit implements an optional check
which will invoke a kernel oops is a blocking operation is
attempted from a work item passed to the system workqueue.

Signed-off-by: Bjarki Arge Andreasen <[email protected]>

Author: bjarki-andreasen

doc/kernel/services/threads/workqueue.rst

@@ -109,6 +109,9 @@ its queue until the handler function finishes executing.
    potentially blocking, as there is no guarantee that work items submitted to
    it do not depend on subsequent work items in the queue to unblock them.
 
+   :kconfig:option:`CONFIG_SYSTEM_WORKQUEUE_NO_BLOCK` enforces that no work
+   items submitted to the system workqueue perform any blocking operations.
+
 The single argument that is passed to a handler function can be ignored if it
 is not required. If the handler function requires additional information about
 the work it is to perform, the work item can be embedded in a larger data

kernel/Kconfig

@@ -600,6 +600,14 @@ config SYSTEM_WORKQUEUE_NO_YIELD
 	  cooperative and a sequence of work items is expected to complete
 	  without yielding.
 
+CONFIG_SYSTEM_WORKQUEUE_NO_BLOCK
+	bool "Select whether system work queue enforces work items dont block"
+	help
+	  By default, the system work queue does not enforce work items
+	  passed to it dont perform blocking operations. Selecting this
+	  enforces that blocking operations are not performed by invoking
+	  a kernel oops if such operations are attempted.
+
 endmenu
 
 menu "Barrier Operations"

kernel/sched.c

@@ -523,6 +523,10 @@ static inline void z_vrfy_k_thread_resume(k_tid_t thread)
 
 static void unready_thread(struct k_thread *thread)
 {
+	if (IS_ENABLED(CONFIG_SYSTEM_WORKQUEUE_NO_BLOCK) && k_is_in_sys_work()) {
+		k_oops();
+	}
+
 	if (z_is_thread_queued(thread)) {
 		dequeue_thread(thread);
 	}