From 06c6796e0304234da65e70577f354cb194086521 Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Tue, 23 May 2023 01:12:26 +0200 Subject: [PATCH] cpu/hotplug: Fix off by one in cpuhp_bringup_mask() cpuhp_bringup_mask() iterates over a cpumask and starts all present CPUs up to a caller provided upper limit. The limit variable is decremented and checked for 0 before invoking cpu_up(), which is obviously off by one and prevents the bringup of the last CPU when the limit is equal to the number of present CPUs. Move the decrement and check after the cpu_up() invocation. Fixes: 18415f33e2ac ("cpu/hotplug: Allow "parallel" bringup up to CPUHP_BP_KICK_AP_STATE") Reported-by: Mark Brown Signed-off-by: Thomas Gleixner Tested-by: Mark Brown Link: https://lore.kernel.org/r/87wn10ufj9.ffs@tglx --- kernel/cpu.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/kernel/cpu.c b/kernel/cpu.c index 005f863a3d2b..88a7ede322bd 100644 --- a/kernel/cpu.c +++ b/kernel/cpu.c @@ -1770,9 +1770,6 @@ static void __init cpuhp_bringup_mask(const struct cpumask *mask, unsigned int n for_each_cpu(cpu, mask) { struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu); - if (!--ncpus) - break; - if (cpu_up(cpu, target) && can_rollback_cpu(st)) { /* * If this failed then cpu_up() might have only @@ -1781,6 +1778,9 @@ static void __init cpuhp_bringup_mask(const struct cpumask *mask, unsigned int n */ WARN_ON(cpuhp_invoke_callback_range(false, cpu, st, CPUHP_OFFLINE)); } + + if (!--ncpus) + break; } }