This is an optimization to bypass the free vector checking if the current CPU has no irq to migrate. This can especially speed up the CPU offline process when there are many CPUs in the system.
Cc: Thomas Gleixner <[email protected]> Cc: Ingo Molnar <[email protected]> Cc: "H. Peter Anvin" <[email protected]> Cc: Prarit Bhargava <[email protected]> Cc: "Rafael J. Wysocki" <[email protected]> Cc: Len Brown <[email protected]> Cc: [email protected] Cc: [email protected] Signed-off-by: Chen Yu <[email protected]> --- arch/x86/kernel/irq.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/arch/x86/kernel/irq.c b/arch/x86/kernel/irq.c index 4d8183b..b9bdc1e 100644 --- a/arch/x86/kernel/irq.c +++ b/arch/x86/kernel/irq.c @@ -394,6 +394,9 @@ int check_irq_vectors_for_cpu_disable(void) !cpumask_subset(&affinity_new, &online_new)) this_count++; } + /* No need to check any further. */ + if (!this_count) + return 0; count = 0; for_each_online_cpu(cpu) { -- 2.7.4
