core: thread_init_threads(): replace dummy thread ctx

When configuring paging, a thread context is needed to keep the VFP
state, but thread context might not have been allocated yet with
CFG_DYN_CONFIG=y so a dummy thread context might be needed until then.
When thread_init_threads() assigns and initializes the real thread
context, update the pointer and count variables using an unpaged
function to make sure that pager code doesn't access the thread context
while it's being replaced. This is needed in later patches with
CFG_DYN_CONFIG=y and CFG_WITH_PAGER=y.

Signed-off-by: Jens Wiklander <[email protected]>

Author: jenswi-linaro

core/kernel/thread.c

@@ -580,16 +580,26 @@ static void init_thread_stacks(void)
 }
 #endif /*CFG_WITH_PAGER*/
 
+static struct thread_ctx *swap_thread_ctx(struct thread_ctx *thr, size_t count)
+{
+	struct thread_ctx *t = threads;
+
+	if (!thr)
+		panic();
+	threads = thr;
+	thread_count = count;
+
+	return t;
+}
+DECLARE_KEEP_PAGER(swap_thread_ctx);
+
 void thread_init_threads(size_t count)
 {
 	size_t n = 0;
 
 	if (IS_ENABLED(CFG_DYN_CONFIG)) {
 		assert(count <= CFG_NUM_THREADS);
-		threads = calloc(count, sizeof(*threads));
-		if (!threads)
-			panic();
-		thread_count = count;
+		free(swap_thread_ctx(calloc(count, sizeof(*threads)), count));
 	} else {
 		assert(count == CFG_NUM_THREADS);
 	}