x86/smpboot: Set online before setting up vectors

There is no reason to set the CPU online after establishing the vectors on
the upcoming CPU. The vector space is protected by the vector lock so no
changes can happen.

Marking the CPU online before setting up the vector space makes tracing
work in the early vector management cpu online code.

Signed-off-by: Thomas Gleixner <[email protected]>
Tested-by: Juergen Gross <[email protected]>
Tested-by: Yu Chen <[email protected]>
Acked-by: Juergen Gross <[email protected]>
Cc: Boris Ostrovsky <[email protected]>
Cc: Tony Luck <[email protected]>
Cc: Marc Zyngier <[email protected]>
Cc: Alok Kataria <[email protected]>
Cc: Joerg Roedel <[email protected]>
Cc: "Rafael J. Wysocki" <[email protected]>
Cc: Steven Rostedt <[email protected]>
Cc: Christoph Hellwig <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Paolo Bonzini <[email protected]>
Cc: Rui Zhang <[email protected]>
Cc: "K. Y. Srinivasan" <[email protected]>
Cc: Arjan van de Ven <[email protected]>
Cc: Dan Williams <[email protected]>
Cc: Len Brown <[email protected]>
Link: https://lkml.kernel.org/r/[email protected]

Author: KAGA-KOKO

arch/x86/kernel/smpboot.c

@@ -254,14 +254,14 @@ static void notrace start_secondary(void *unused)
 	check_tsc_sync_target();
 
 	/*
-	 * Lock vector_lock and initialize the vectors on this cpu
-	 * before setting the cpu online. We must set it online with
-	 * vector_lock held to prevent a concurrent setup/teardown
-	 * from seeing a half valid vector space.
+	 * Lock vector_lock, set CPU online and bring the vector
+	 * allocator online. Online must be set with vector_lock held
+	 * to prevent a concurrent irq setup/teardown from seeing a
+	 * half valid vector space.
 	 */
 	lock_vector_lock();
-	lapic_online();
 	set_cpu_online(smp_processor_id(), true);
+	lapic_online();
 	unlock_vector_lock();
 	cpu_set_state_online(smp_processor_id());
 	x86_platform.nmi_init();