| From 90ae06bd083cc66f3dd1b7d91c4d636ac1ee881d Mon Sep 17 00:00:00 2001 |
| From: Sasha Levin <sashal@kernel.org> |
| Date: Wed, 28 Oct 2020 14:27:42 -0400 |
| Subject: s390/smp: move rcu_cpu_starting() earlier |
| |
| From: Qian Cai <cai@redhat.com> |
| |
| [ Upstream commit de5d9dae150ca1c1b5c7676711a9ca139d1a8dec ] |
| |
| The call to rcu_cpu_starting() in smp_init_secondary() is not early |
| enough in the CPU-hotplug onlining process, which results in lockdep |
| splats as follows: |
| |
| WARNING: suspicious RCU usage |
| ----------------------------- |
| kernel/locking/lockdep.c:3497 RCU-list traversed in non-reader section!! |
| |
| other info that might help us debug this: |
| |
| RCU used illegally from offline CPU! |
| rcu_scheduler_active = 1, debug_locks = 1 |
| no locks held by swapper/1/0. |
| |
| Call Trace: |
| show_stack+0x158/0x1f0 |
| dump_stack+0x1f2/0x238 |
| __lock_acquire+0x2640/0x4dd0 |
| lock_acquire+0x3a8/0xd08 |
| _raw_spin_lock_irqsave+0xc0/0xf0 |
| clockevents_register_device+0xa8/0x528 |
| init_cpu_timer+0x33e/0x468 |
| smp_init_secondary+0x11a/0x328 |
| smp_start_secondary+0x82/0x88 |
| |
| This is avoided by moving the call to rcu_cpu_starting up near the |
| beginning of the smp_init_secondary() function. Note that the |
| raw_smp_processor_id() is required in order to avoid calling into |
| lockdep before RCU has declared the CPU to be watched for readers. |
| |
| Link: https://lore.kernel.org/lkml/160223032121.7002.1269740091547117869.tip-bot2@tip-bot2/ |
| Signed-off-by: Qian Cai <cai@redhat.com> |
| Acked-by: Paul E. McKenney <paulmck@kernel.org> |
| Signed-off-by: Heiko Carstens <hca@linux.ibm.com> |
| Signed-off-by: Sasha Levin <sashal@kernel.org> |
| --- |
| arch/s390/kernel/smp.c | 3 ++- |
| 1 file changed, 2 insertions(+), 1 deletion(-) |
| |
| diff --git a/arch/s390/kernel/smp.c b/arch/s390/kernel/smp.c |
| index 85700bd85f98d..3b4c3140c18e7 100644 |
| --- a/arch/s390/kernel/smp.c |
| +++ b/arch/s390/kernel/smp.c |
| @@ -855,13 +855,14 @@ void __init smp_detect_cpus(void) |
| |
| static void smp_init_secondary(void) |
| { |
| - int cpu = smp_processor_id(); |
| + int cpu = raw_smp_processor_id(); |
| |
| S390_lowcore.last_update_clock = get_tod_clock(); |
| restore_access_regs(S390_lowcore.access_regs_save_area); |
| set_cpu_flag(CIF_ASCE_PRIMARY); |
| set_cpu_flag(CIF_ASCE_SECONDARY); |
| cpu_init(); |
| + rcu_cpu_starting(cpu); |
| preempt_disable(); |
| init_cpu_timer(); |
| vtime_init(); |
| -- |
| 2.27.0 |
| |