[patch v3 15/36] x86/smpboot: Remove wait for cpu_online()

Thomas Gleixner
2023-05-08T19:44:56Z

From: Thomas Gleixner <tglx@linutronix.de>

Now that the core code drops sparse_irq_lock after the idle thread
synchronized, it's pointless to wait for the AP to mark itself online.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Michael Kelley <mikelley@microsoft.com>

---
arch/x86/kernel/smpboot.c | 26 ++------------------------
1 file changed, 2 insertions(+), 24 deletions(-)
---

--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -281,7 +281,6 @@ static void notrace start_secondary(void
* half valid vector space.
*/
lock_vector_lock();
- /* Sync point with do_wait_cpu_online() */
set_cpu_online(smp_processor_id(), true);
lapic_online();
unlock_vector_lock();
@@ -1110,20 +1109,6 @@ static int wait_cpu_initialized(unsigned
return 0;
}

-/*
- * Bringup step three: Wait for the target AP to reach set_cpu_online() in
- * start_secondary().
- */
-static void wait_cpu_online(unsigned int cpu)
-{
- /*
- * Wait for the AP to mark itself online, so the core caller
- * can drop sparse_irq_lock.
- */
- while (!cpu_online(cpu))
- schedule();
-}
-
static int native_kick_ap(unsigned int cpu, struct task_struct *tidle)
{
int apicid = apic->cpu_present_to_apicid(cpu);
@@ -1170,16 +1155,9 @@ int native_cpu_up(unsigned int cpu, stru
int ret;

ret = native_kick_ap(cpu, tidle);
- if (ret)
- goto out;
-
- ret = wait_cpu_initialized(cpu);
- if (ret)
- goto out;
-
- wait_cpu_online(cpu);
+ if (!ret)
+ ret = wait_cpu_initialized(cpu);

-out:
/* Cleanup possible dangling ends... */
if (x86_platform.legacy.warm_reset)
smpboot_restore_warm_reset_vector();