Messages in this thread | | | From | Ryan Chen <> | Date | Tue, 10 Dec 2019 15:55:57 +0800 | Subject | Re: [PATCH] x86/resctrl: fix an imbalance in domain_remove_cpu |
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Hi Qian,
On Sun, Dec 8, 2019 at 12:14 PM Qian Cai <cai@lca.pw> wrote: > > domain_add_cpu() calls domain_setup_mon_state() only when r->mon_capable > is true where it will initialize d->mbm_over. However, > domain_remove_cpu() calls cancel_delayed_work(&d->mbm_over) without > checking r->mon_capable. Hence, it triggers a debugobjects warning when > offlining CPUs because those timer debugobjects are never initialized. > Could you elaborate a little more on the failure symptom? If I understand correctly, the error you described was due to r->mon_capable set to false while is_mbm_enabled() returns true? Which means on this platform rdt_mon_features is non zero? And in get_rdt_mon_resources() it will invoke rdt_get_mon_l3_config(), however the only possible failure to do not set r->mon_capable is that it failed in dom_data_init() due to kcalloc() failure? Then the logic in get_rdt_resources() is that it will ignore the return error if rdt allocate feature is supported on this platform? If this is the case, the r->mon_capable is not an indicator for whether the overflow thread has been created, right? Can we simply remove the check of r->mon_capable in domain_add_cpu() and invoke domain_setup_mon_state() directly? > ODEBUG: assert_init not available (active state 0) object type: > timer_list hint: 0x0 > WARNING: CPU: 143 PID: 789 at lib/debugobjects.c:484 > debug_print_object+0xfe/0x140 > Hardware name: HP Synergy 680 Gen9/Synergy 680 Gen9 Compute Module, BIOS > I40 05/23/2018 > RIP: 0010:debug_print_object+0xfe/0x140 > Call Trace: > debug_object_assert_init+0x1f5/0x240 > del_timer+0x6f/0xf0 > try_to_grab_pending+0x42/0x3c0 > cancel_delayed_work+0x7d/0x150 > resctrl_offline_cpu+0x3c0/0x520 > cpuhp_invoke_callback+0x197/0x1120 > cpuhp_thread_fun+0x252/0x2f0 > smpboot_thread_fn+0x255/0x440 > kthread+0x1e6/0x210 > ret_from_fork+0x3a/0x50 > > Fixes: e33026831bdb ("x86/intel_rdt/mbm: Handle counter overflow") > Signed-off-by: Qian Cai <cai@lca.pw> > --- > arch/x86/kernel/cpu/resctrl/core.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/arch/x86/kernel/cpu/resctrl/core.c b/arch/x86/kernel/cpu/resctrl/core.c > index 03eb90d00af0..89049b343c7a 100644 > --- a/arch/x86/kernel/cpu/resctrl/core.c > +++ b/arch/x86/kernel/cpu/resctrl/core.c > @@ -618,7 +618,7 @@ static void domain_remove_cpu(int cpu, struct rdt_resource *r) > if (static_branch_unlikely(&rdt_mon_enable_key)) > rmdir_mondata_subdir_allrdtgrp(r, d->id); > list_del(&d->list); > - if (is_mbm_enabled()) > + if (r->mon_capable && is_mbm_enabled()) > cancel_delayed_work(&d->mbm_over); Humm, it looks like there are two places within this function invoked cancel_delayed_work(&d->mbm_over), why not adding the check for both of them?
thanks, Y
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