On Wed, Oct 28, 2020 at 10:39:47AM -0400, Qian Cai wrote: > On Tue, 2020-10-27 at 20:01 -0700, Paul E. McKenney wrote: > > If I have the right email thread associated with the right fixes, these > > commits in -rcu should be what you are looking for: > > > > 73b658b6b7d5 ("rcu: Prevent lockdep-RCU splats on lock acquisition/release") > > 626b79aa935a ("x86/smpboot: Move rcu_cpu_starting() earlier") > > > > And maybe this one as well: > > > > 3a6f638cb95b ("rcu,ftrace: Fix ftrace recursion") > > > > Please let me know if these commits do not fix things. > While those patches silence the warnings for x86. Other arches are still > suffering. It is only after applying the patch from Boqun below fixed > everything. Fair point! > Is it a good idea for Boqun to write a formal patch or we should fix all arches > individually like "x86/smpboot: Move rcu_cpu_starting() earlier"? By Boqun's patch, you mean the change to debug_lockdep_rcu_enabled() shown below? Peter Zijlstra showed that real failures can happen, so we do not want to cover them up. So we are firmly in "fix all architectures" space here, sorry! I am happy to accumulate those patches, but cannot commit to creating or testing them. Thanx, Paul > > > > diff --git a/kernel/rcu/update.c b/kernel/rcu/update.c > > > > index 39334d2d2b37..35d9bab65b75 100644 > > > > --- a/kernel/rcu/update.c > > > > +++ b/kernel/rcu/update.c > > > > @@ -275,8 +275,8 @@ EXPORT_SYMBOL_GPL(rcu_callback_map); > > > > > > > > noinstr int notrace debug_lockdep_rcu_enabled(void) > > > > { > > > > - return rcu_scheduler_active != RCU_SCHEDULER_INACTIVE && debug_locks && > > > > - current->lockdep_recursion == 0; > > > > + return rcu_scheduler_active != RCU_SCHEDULER_INACTIVE && > > > > + __lockdep_enabled; > > > > } > > > > EXPORT_SYMBOL_GPL(debug_lockdep_rcu_enabled); > > The warnings for each arch are: > > == powerpc == > [ 0.176044][ T1] smp: Bringing up secondary CPUs ... > [ 0.179731][ T0] > [ 0.179734][ T0] ============================= > [ 0.179736][ T0] WARNING: suspicious RCU usage > [ 0.179739][ T0] 5.10.0-rc1-next-20201028+ #2 Not tainted > [ 0.179741][ T0] ----------------------------- > [ 0.179744][ T0] kernel/locking/lockdep.c:3497 RCU-list traversed in non-reader section!! > [ 0.179745][ T0] > [ 0.179745][ T0] other info that might help us debug this: > [ 0.179745][ T0] > [ 0.179748][ T0] > [ 0.179748][ T0] RCU used illegally from offline CPU! > [ 0.179748][ T0] rcu_scheduler_active = 1, debug_locks = 1 > [ 0.179750][ T0] no locks held by swapper/1/0. > [ 0.179752][ T0] > [ 0.179752][ T0] stack backtrace: > [ 0.179757][ T0] CPU: 1 PID: 0 Comm: swapper/1 Not tainted 5.10.0-rc1-next-20201028+ #2 > [ 0.179759][ T0] Call Trace: > [ 0.179767][ T0] [c000000015b27ab0] [c000000000657188] dump_stack+0xec/0x144 (unreliable) > [ 0.179776][ T0] [c000000015b27af0] [c00000000014d0d4] lockdep_rcu_suspicious+0x128/0x14c > [ 0.179782][ T0] [c000000015b27b70] [c000000000148920] __lock_acquire+0x1060/0x1c60 > [ 0.179788][ T0] [c000000015b27ca0] [c00000000014a1d0] lock_acquire+0x140/0x5f0 > [ 0.179794][ T0] [c000000015b27d90] [c0000000008f22f4] _raw_spin_lock_irqsave+0x64/0xb0 > [ 0.179801][ T0] [c000000015b27dd0] [c0000000001a1094] clockevents_register_device+0x74/0x270 > [ 0.179808][ T0] [c000000015b27e80] [c00000000001f194] register_decrementer_clockevent+0x94/0x110 > [ 0.179814][ T0] [c000000015b27ef0] [c00000000003fd84] start_secondary+0x134/0x800 > [ 0.179819][ T0] [c000000015b27f90] [c00000000000c454] start_secondary_prolog+0x10/0x14 > [ 0.179855][ T0] > [ 0.179857][ T0] ============================= > [ 0.179858][ T0] WARNING: suspicious RCU usage > [ 0.179860][ T0] 5.10.0-rc1-next-20201028+ #2 Not tainted > [ 0.179862][ T0] ----------------------------- > [ 0.179864][ T0] kernel/locking/lockdep.c:886 RCU-list traversed in non-reader section!! > [ 0.179866][ T0] > [ 0.179866][ T0] other info that might help us debug this: > [ 0.179866][ T0] > [ 0.179868][ T0] > [ 0.179868][ T0] RCU used illegally from offline CPU! > [ 0.179868][ T0] rcu_scheduler_active = 1, debug_locks = 1 > [ 0.179870][ T0] no locks held by swapper/1/0. > [ 0.179871][ T0] > [ 0.179871][ T0] stack backtrace: > [ 0.179875][ T0] CPU: 1 PID: 0 Comm: swapper/1 Not tainted 5.10.0-rc1-next-20201028+ #2 > [ 0.179876][ T0] Call Trace: > [ 0.179880][ T0] [c000000015b27980] [c000000000657188] dump_stack+0xec/0x144 (unreliable) > [ 0.179886][ T0] [c000000015b279c0] [c00000000014d0d4] lockdep_rcu_suspicious+0x128/0x14c > [ 0.179892][ T0] [c000000015b27a40] [c00000000014b010] register_lock_class+0x680/0xc70 > [ 0.179896][ T0] [c000000015b27b50] [c00000000014795c] __lock_acquire+0x9c/0x1c60 > [ 0.179901][ T0] [c000000015b27c80] [c00000000014a1d0] lock_acquire+0x140/0x5f0 > [ 0.179906][ T0] [c000000015b27d70] [c0000000008f22f4] _raw_spin_lock_irqsave+0x64/0xb0 > [ 0.179912][ T0] [c000000015b27db0] [c0000000003a2fb4] __delete_object+0x44/0x80 > [ 0.179917][ T0] [c000000015b27de0] [c00000000035a964] slab_free_freelist_hook+0x174/0x300 > [ 0.179921][ T0] [c000000015b27e50] [c00000000035f848] kfree+0xf8/0x500 > [ 0.179926][ T0] [c000000015b27ed0] [c000000000656878] free_cpumask_var+0x18/0x30 > [ 0.179931][ T0] [c000000015b27ef0] [c00000000003fff0] start_secondary+0x3a0/0x800 > add_cpu_to_masks at arch/powerpc/kernel/smp.c:1390 > (inlined by) start_secondary at arch/powerpc/kernel/smp.c:1420 > [ 0.179936][ T0] [c000000015b27f90] [c00000000000c454] start_secondary_prolog+0x10/0x14 > [ 0.955418][ T1] smp: Brought up 2 nodes, 128 CPUs > > == arm64 == > [ 0.473124][ T0] CPU1: Booted secondary processor 0x0000000100 [0x431f0af1] > [ 0.473180][ C1] > [ 0.473183][ C1] ============================= > [ 0.473186][ C1] WARNING: suspicious RCU usage > [ 0.473188][ C1] 5.10.0-rc1-next-20201028+ #3 Not tainted > [ 0.473190][ C1] ----------------------------- > [ 0.473193][ C1] kernel/locking/lockdep.c:3497 RCU-list traversed in non-reader section!! > [ 0.473194][ C1] > [ 0.473197][ C1] other info that might help us debug this: > [ 0.473198][ C1] > [ 0.473200][ C1] > [ 0.473202][ C1] RCU used illegally from offline CPU! > [ 0.473204][ C1] rcu_scheduler_active = 1, debug_locks = 1 > [ 0.473206][ C1] no locks held by swapper/1/0. > [ 0.473208][ C1] > [ 0.473210][ C1] stack backtrace: > [ 0.473212][ C1] CPU: 1 PID: 0 Comm: swapper/1 Not tainted 5.10.0-rc1-next-20201028+ #3 > [ 0.473215][ C1] Call trace: > [ 0.473217][ C1] dump_backtrace+0x0/0x3c8 > [ 0.473219][ C1] show_stack+0x14/0x60 > [ 0.473221][ C1] dump_stack+0x14c/0x1c4 > [ 0.473223][ C1] lockdep_rcu_suspicious+0x134/0x14c > [ 0.473225][ C1] __lock_acquire+0x1c30/0x2600 > [ 0.473227][ C1] lock_acquire+0x274/0xc48 > [ 0.473229][ C1] _raw_spin_lock+0xc8/0x140 > [ 0.473231][ C1] vprintk_emit+0x90/0x3d0 > [ 0.473233][ C1] vprintk_default+0x34/0x40 > [ 0.473235][ C1] vprintk_func+0x378/0x590 > [ 0.473236][ C1] printk+0xa8/0xd4 > [ 0.473239][ C1] __cpuinfo_store_cpu+0x71c/0x868 > [ 0.473241][ C1] cpuinfo_store_cpu+0x2c/0xc8 > [ 0.473243][ C1] secondary_start_kernel+0x244/0x318 > [ 0.547541][ T0] Detected PIPT I-cache on CPU2 > [ 0.547562][ T0] GICv3: CPU2: found redistributor 200 region 0:0x0000000401100000 > > == s390 == > 00: [ 0.603404] WARNING: suspicious RCU usage > 00: [ 0.603408] 5.10.0-rc1-next-20201027 #1 Not tainted > 00: [ 0.603409] ----------------------------- > 00: [ 0.603459] kernel/locking/lockdep.c:3497 RCU-list traversed in non-reade > 00: r section!! > 00: [ 0.603460] > 00: [ 0.603460] other info that might help us debug this: > 00: [ 0.603460] > 00: [ 0.603462] > 00: [ 0.603462] RCU used illegally from offline CPU! > 00: [ 0.603462] rcu_scheduler_active = 1, debug_locks = 1 > 00: [ 0.603463] no locks held by swapper/1/0. > 00: [ 0.603464] > 00: [ 0.603464] stack backtrace: > 00: [ 0.603467] CPU: 1 PID: 0 Comm: swapper/1 Not tainted 5.10.0-rc1-next-202 > 00: 01027 #1 > 00: [ 0.603469] Hardware name: IBM 2964 N96 400 (z/VM 6.4.0) > 00: [ 0.603471] Call Trace: > 00: [ 0.603484] [<00000000d262a778>] show_stack+0x158/0x1f0 > 00: [ 0.603487] [<00000000d2635872>] dump_stack+0x1f2/0x238 > 00: [ 0.603491] [<00000000d167a550>] __lock_acquire+0x2640/0x4dd0 > 00: [ 0.603493] [<00000000d167eda8>] lock_acquire+0x3a8/0xd08 > 00: [ 0.603498] [<00000000d265b088>] _raw_spin_lock_irqsave+0xc0/0xf0 > 00: [ 0.603502] [<00000000d17103f8>] clockevents_register_device+0xa8/0x528 > 00: > 00: [ 0.603516] [<00000000d14f5246>] init_cpu_timer+0x33e/0x468 > 00: [ 0.603521] [<00000000d151f44a>] smp_init_secondary+0x11a/0x328 > 00: [ 0.603525] [<00000000d151f32a>] smp_start_secondary+0x82/0x88 >
![]() |