From: Qian Cai cai@redhat.com
[ Upstream commit ce3d31ad3cac765484463b4f5a0b6b1f8f1a963e ]
The call to rcu_cpu_starting() in secondary_start_kernel() 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: dump_backtrace+0x0/0x3c8 show_stack+0x14/0x60 dump_stack+0x14c/0x1c4 lockdep_rcu_suspicious+0x134/0x14c __lock_acquire+0x1c30/0x2600 lock_acquire+0x274/0xc48 _raw_spin_lock+0xc8/0x140 vprintk_emit+0x90/0x3d0 vprintk_default+0x34/0x40 vprintk_func+0x378/0x590 printk+0xa8/0xd4 __cpuinfo_store_cpu+0x71c/0x868 cpuinfo_store_cpu+0x2c/0xc8 secondary_start_kernel+0x244/0x318
This is avoided by moving the call to rcu_cpu_starting up near the beginning of the secondary_start_kernel() function.
Signed-off-by: Qian Cai cai@redhat.com Acked-by: Paul E. McKenney paulmck@kernel.org Link: https://lore.kernel.org/lkml/160223032121.7002.1269740091547117869.tip-bot2@... Link: https://lore.kernel.org/r/20201028182614.13655-1-cai@redhat.com Signed-off-by: Will Deacon will@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- arch/arm64/kernel/smp.c | 1 + 1 file changed, 1 insertion(+)
diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c index 8cd6316a0d833..3e0fd4e6bcdcb 100644 --- a/arch/arm64/kernel/smp.c +++ b/arch/arm64/kernel/smp.c @@ -214,6 +214,7 @@ asmlinkage notrace void secondary_start_kernel(void) if (system_uses_irq_prio_masking()) init_gic_priority_masking();
+ rcu_cpu_starting(cpu); preempt_disable(); trace_hardirqs_off();