kernel: smp: introduce k_smp_cpu_resume
This provides a path to resume a previously suspended CPU.
This differs from k_smp_cpu_start() where per-CPU kernel
structs are not initialized such that execution context
can be saved during suspend and restored during resume.
Though the actual context saving and restoring are
platform specific.
Signed-off-by: Daniel Leung <daniel.leung@intel.com>
diff --git a/kernel/smp.c b/kernel/smp.c
index 7fe4f85..ff23171 100644
--- a/kernel/smp.c
+++ b/kernel/smp.c
@@ -42,6 +42,14 @@
/** Argument to @ref cpu_start_fn.fn. */
void *arg;
+
+ /** Invoke scheduler after CPU has started if true. */
+ bool invoke_sched;
+
+#ifdef CONFIG_SYS_CLOCK_EXISTS
+ /** True if smp_timer_init() needs to be called. */
+ bool reinit_timer;
+#endif
} cpu_start_fn;
static struct k_spinlock cpu_start_lock;
@@ -111,7 +119,7 @@
}
#endif
-static inline FUNC_NORETURN void smp_init_top(void *arg)
+static inline void smp_init_top(void *arg)
{
struct k_thread dummy_thread;
struct cpu_start_cb *csc = arg;
@@ -124,13 +132,10 @@
*/
wait_for_start_signal(&cpu_start_flag);
- /* Initialize the dummy thread struct so that
- * the scheduler can schedule actual threads to run.
- */
- z_dummy_thread_init(&dummy_thread);
-
#ifdef CONFIG_SYS_CLOCK_EXISTS
- smp_timer_init();
+ if ((csc == NULL) || csc->reinit_timer) {
+ smp_timer_init();
+ }
#endif
/* Do additional initialization steps if needed. */
@@ -138,6 +143,16 @@
csc->fn(csc->arg);
}
+ if ((csc != NULL) && !csc->invoke_sched) {
+ /* Don't invoke scheduler. */
+ return;
+ }
+
+ /* Initialize the dummy thread struct so that
+ * the scheduler can schedule actual threads to run.
+ */
+ z_dummy_thread_init(&dummy_thread);
+
/* Let scheduler decide what thread to run next. */
z_swap_unlocked();
@@ -146,9 +161,6 @@
static void start_cpu(int id, struct cpu_start_cb *csc)
{
- /* Initialize various CPU structs related to this CPU. */
- z_init_cpu(id);
-
/* Clear the ready flag so the newly powered up CPU can
* signal that it has powered up.
*/
@@ -172,6 +184,40 @@
cpu_start_fn.fn = fn;
cpu_start_fn.arg = arg;
+ cpu_start_fn.invoke_sched = true;
+
+#ifdef CONFIG_SYS_CLOCK_EXISTS
+ cpu_start_fn.reinit_timer = true;
+#endif
+
+ /* We are only starting one CPU so we do not need to synchronize
+ * across all CPUs using the start_flag. So just set it to 1.
+ */
+ (void)atomic_set(&cpu_start_flag, 1); /* async, don't care */
+
+ /* Initialize various CPU structs related to this CPU. */
+ z_init_cpu(id);
+
+ /* Start the CPU! */
+ start_cpu(id, &cpu_start_fn);
+
+ k_spin_unlock(&cpu_start_lock, key);
+}
+
+void k_smp_cpu_resume(int id, smp_init_fn fn, void *arg,
+ bool reinit_timer, bool invoke_sched)
+{
+ k_spinlock_key_t key = k_spin_lock(&cpu_start_lock);
+
+ cpu_start_fn.fn = fn;
+ cpu_start_fn.arg = arg;
+ cpu_start_fn.invoke_sched = invoke_sched;
+
+#ifdef CONFIG_SYS_CLOCK_EXISTS
+ cpu_start_fn.reinit_timer = reinit_timer;
+#else
+ ARG_UNUSED(reinit_timer);
+#endif
/* We are only starting one CPU so we do not need to synchronize
* across all CPUs using the start_flag. So just set it to 1.
@@ -195,6 +241,7 @@
unsigned int num_cpus = arch_num_cpus();
for (int i = 1; i < num_cpus; i++) {
+ z_init_cpu(i);
start_cpu(i, NULL);
}
