[kernel][thread] Hook uthread context switch

thread_resched() calls into libuthread to switch userspace.

Change-Id: Iad8e5ade175316eb784410c369c6473b68b6f5d6
Signed-off-by: Satya Popuri <popuri@google.com>

include/kernel/thread.h

@@ -46,6 +46,9 @@ typedef int (*thread_start_routine)(void *arg);
 
 /* thread local storage */
 enum thread_tls_list {
+#ifdef WITH_LIB_UTHREAD
+	TLS_ENTRY_UTHREAD,
+#endif
 	MAX_TLS_ENTRY
 };
 
@@ -140,6 +143,10 @@ void thread_preempt(void); /* get preempted (inserted into head of run queue) */
 void thread_block(void); /* block on something and reschedule */
 void thread_unblock(thread_t *t, bool resched); /* go back in the run queue */
 
+#ifdef WITH_LIB_UTHREAD
+void uthread_context_switch(thread_t *oldthread, thread_t *newthread);
+#endif
+
 /* called on every timer tick for the scheduler to do quantum expiration */
 enum handler_return thread_timer_tick(void);
 

kernel/thread.c

@@ -563,6 +563,9 @@ void thread_resched(void)
 		newthread->priority, newthread->flags);
 #endif
 
+#ifdef WITH_LIB_UTHREAD
+	uthread_context_switch(oldthread, newthread);
+#endif
 	arch_context_switch(oldthread, newthread);
 }