Commit e464640c authored by Thomas Gleixner's avatar Thomas Gleixner Committed by Peter Zijlstra
Browse files

x86/smpboot: Remove wait for cpu_online() 



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: default avatarThomas Gleixner <tglx@linutronix.de>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: default avatarMichael Kelley <mikelley@microsoft.com>
Tested-by: default avatarOleksandr Natalenko <oleksandr@natalenko.name>
Tested-by: Helge Deller <deller@gmx.de> # parisc
Tested-by: Guilherme G. Piccoli <gpiccoli@igalia.com> # Steam Deck
Link: https://lore.kernel.org/r/20230512205256.316417181@linutronix.de
parent 22b612e2

arch/x86/kernel/smpboot.c

+2 −24
Original line number Diff line number Diff line
@@ -275,7 +275,6 @@ static void notrace start_secondary(void *unused) 
	 * 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();
@@ -1104,20 +1103,6 @@ static int wait_cpu_initialized(unsigned int cpu) 
	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);
@@ -1164,16 +1149,9 @@ int native_cpu_up(unsigned int cpu, struct task_struct *tidle) 
	int ret;



	ret = native_kick_ap(cpu, tidle);

	if (ret)

		goto out;



	if (!ret)

		ret = wait_cpu_initialized(cpu);

	if (ret)

		goto out;



	wait_cpu_online(cpu);



out:

	/* Cleanup possible dangling ends... */

	if (x86_platform.legacy.warm_reset)

		smpboot_restore_warm_reset_vector();