From 6b2c08f989250c54f31b53dba9ace863a1f3fff6 Mon Sep 17 00:00:00 2001 From: Thiago Jung Bauermann Date: Wed, 4 Oct 2017 21:04:30 -0300 Subject: [PATCH] powerpc: Don't call lockdep_assert_cpus_held() from arch_update_cpu_topology() It turns out that not all paths calling arch_update_cpu_topology() hold cpu_hotplug_lock, but that's OK because those paths can't race with any concurrent hotplug events. Warnings were reported with the following trace: lockdep_assert_cpus_held arch_update_cpu_topology sched_init_domains sched_init_smp kernel_init_freeable kernel_init ret_from_kernel_thread Which is safe because it's called early in boot when hotplug is not live yet. And also this trace: lockdep_assert_cpus_held arch_update_cpu_topology partition_sched_domains cpuset_update_active_cpus sched_cpu_deactivate cpuhp_invoke_callback cpuhp_down_callbacks cpuhp_thread_fun smpboot_thread_fn kthread ret_from_kernel_thread Which is safe because it's called as part of CPU hotplug, so although we don't hold the CPU hotplug lock, there is another thread driving the CPU hotplug operation which does hold the lock, and there is no race. Thanks to tglx for deciphering it for us. Fixes: 3e401f7a2e51 ("powerpc: Only obtain cpu_hotplug_lock if called by rtasd") Signed-off-by: Thiago Jung Bauermann Signed-off-by: Michael Ellerman --- arch/powerpc/mm/numa.c | 1 - 1 file changed, 1 deletion(-) diff --git a/arch/powerpc/mm/numa.c b/arch/powerpc/mm/numa.c index b95c584ce19d..a51df9ef529d 100644 --- a/arch/powerpc/mm/numa.c +++ b/arch/powerpc/mm/numa.c @@ -1438,7 +1438,6 @@ out: int arch_update_cpu_topology(void) { - lockdep_assert_cpus_held(); return numa_update_cpu_topology(true); } -- 2.30.2