From 45e565b55b2fc0f731f1b66a706f74301c7cd7f3 Mon Sep 17 00:00:00 2001 From: Stefan Wiehler Date: Mon, 6 Nov 2023 13:12:07 +0100 Subject: [PATCH] mips/smp: Call rcutree_report_cpu_starting() earlier commit 55702ec9603ebeffb15e6f7b113623fe1d8872f4 upstream. rcutree_report_cpu_starting() must be called before clockevents_register_device() to avoid the following lockdep splat triggered by calling list_add() when CONFIG_PROVE_RCU_LIST=y: WARNING: suspicious RCU usage ... ----------------------------- kernel/locking/lockdep.c:3680 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+0x64/0x158 [] dump_stack_lvl+0x90/0xc4 [] __lock_acquire+0x1404/0x2940 [] lock_acquire+0x14c/0x448 [] _raw_spin_lock_irqsave+0x50/0x88 [] clockevents_register_device+0x60/0x1e8 [] r4k_clockevent_init+0x220/0x3a0 [] start_secondary+0x50/0x3b8 raw_smp_processor_id() is required in order to avoid calling into lockdep before RCU has declared the CPU to be watched for readers. See also commit 29368e093921 ("x86/smpboot: Move rcu_cpu_starting() earlier"), commit de5d9dae150c ("s390/smp: move rcu_cpu_starting() earlier") and commit 99f070b62322 ("powerpc/smp: Call rcu_cpu_starting() earlier"). Signed-off-by: Stefan Wiehler Reviewed-by: Huacai Chen Signed-off-by: Thomas Bogendoerfer Signed-off-by: Greg Kroah-Hartman --- arch/mips/kernel/smp.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/arch/mips/kernel/smp.c b/arch/mips/kernel/smp.c index 1d93b85271ba..002c91fcb842 100644 --- a/arch/mips/kernel/smp.c +++ b/arch/mips/kernel/smp.c @@ -333,10 +333,11 @@ early_initcall(mips_smp_ipi_init); */ asmlinkage void start_secondary(void) { - unsigned int cpu; + unsigned int cpu = raw_smp_processor_id(); cpu_probe(); per_cpu_trap_init(false); + rcu_cpu_starting(cpu); mips_clockevent_init(); mp_ops->init_secondary(); cpu_report(); @@ -348,7 +349,6 @@ asmlinkage void start_secondary(void) */ calibrate_delay(); - cpu = smp_processor_id(); cpu_data[cpu].udelay_val = loops_per_jiffy; set_cpu_sibling_map(cpu);