linux-kernel - Re: [PATCH] x86, mce, therm_throt: Optimize notifications of thermal throttle

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Date:   Sat, 08 Feb 2020 22:24:42 +0000
From:   Chris Wilson <chris@...is-wilson.co.uk>
To:     Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
        bberg@...hat.com, bp@...en8.de, hpa@...or.com, mingo@...hat.com,
        tglx@...utronix.de, tony.luck@...el.com
Cc:     x86@...nel.org, linux-edac@...r.kernel.org,
        linux-kernel@...r.kernel.org, hdegoede@...hat.com,
        ckellner@...hat.com,
        Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
Subject: Re: [PATCH] x86, mce, therm_throt: Optimize notifications of thermal throttle

Quoting Srinivas Pandruvada (2019-11-11 21:43:12)
> +static void throttle_active_work(struct work_struct *work)
> +{
> +       struct _thermal_state *state = container_of(to_delayed_work(work),
> +                                               struct _thermal_state, therm_work);
> +       unsigned int i, avg, this_cpu = smp_processor_id();
> +       u64 now = get_jiffies_64();
> +       bool hot;
> +       u8 temp;

<6> [198.901895] [IGT] perf_pmu: starting subtest cpu-hotplug
<4> [199.088851] IRQ 24: no longer affine to CPU0
<4> [199.088871] IRQ 25: no longer affine to CPU0
<6> [199.091679] smpboot: CPU 0 is now offline
<6> [200.122204] smpboot: Booting Node 0 Processor 0 APIC 0x0
<6> [200.297267] smpboot: CPU 1 is now offline
<3> [201.218812] BUG: using smp_processor_id() in preemptible [00000000] code: kworker/1:0/17
<4> [201.218974] caller is throttle_active_work+0x12/0x280
<4> [201.218985] CPU: 0 PID: 17 Comm: kworker/1:0 Tainted: G     U            5.5.0-CI-CI_DRM_7867+ #1
<4> [201.218991] Hardware name: MSI MS-7924/Z97M-G43(MS-7924), BIOS V1.12 02/15/2016
<4> [201.219001] Workqueue: events throttle_active_work
<4> [201.219009] Call Trace:
<4> [201.219021]  dump_stack+0x71/0x9b
<4> [201.219035]  debug_smp_processor_id+0xad/0xb0
<4> [201.219047]  throttle_active_work+0x12/0x280
<4> [201.219063]  process_one_work+0x26a/0x620
<4> [201.219087]  worker_thread+0x37/0x380
<4> [201.219103]  ? process_one_work+0x620/0x620
<4> [201.219110]  kthread+0x119/0x130
<4> [201.219119]  ? kthread_park+0x80/0x80
<4> [201.219134]  ret_from_fork+0x3a/0x50
<6> [201.315866] x86: Booting SMP configuration:
<6> [201.315880] smpboot: Booting Node 0 Processor 1 APIC 0x2
<4> [201.319814] ------------[ cut here ]------------
<3> [201.319832] ODEBUG: init active (active state 0) object type: timer_list hint: delayed_work_timer_fn+0x0/0x10
<4> [201.319971] WARNING: CPU: 1 PID: 14 at lib/debugobjects.c:484 debug_print_object+0x67/0x90
<4> [201.319977] Modules linked in: vgem snd_hda_codec_hdmi i915 mei_hdcp x86_pkg_temp_thermal coretemp snd_hda_codec_realtek crct10dif_pclmul snd_hda_codec_generic crc32_pclmul snd_hda_intel snd_intel_dspcfg snd_hda_codec ghash_clmulni_intel snd_hwdep snd_hda_core snd_pcm mei_me r8169 mei realtek lpc_ich prime_numbers
<4> [201.320023] CPU: 1 PID: 14 Comm: cpuhp/1 Tainted: G     U            5.5.0-CI-CI_DRM_7867+ #1
<4> [201.320029] Hardware name: MSI MS-7924/Z97M-G43(MS-7924), BIOS V1.12 02/15/2016
<4> [201.320038] RIP: 0010:debug_print_object+0x67/0x90
<4> [201.320046] Code: 83 c2 01 8b 4b 14 4c 8b 45 00 89 15 17 f7 8b 02 8b 53 10 4c 89 e6 48 c7 c7 b0 ce 31 82 48 8b 14 d5 00 37 07 82 e8 89 7b b8 ff <0f> 0b 5b 83 05 33 fb 21 01 01 5d 41 5c c3 83 05 28 fb 21 01 01 c3
<4> [201.320053] RSP: 0000:ffffc900000dbd40 EFLAGS: 00010286
<4> [201.320060] RAX: 0000000000000000 RBX: ffff888408665d68 RCX: 0000000000000001
<4> [201.320066] RDX: 0000000080000001 RSI: ffff88840d6e30f8 RDI: 00000000ffffffff
<4> [201.320072] RBP: ffffffff826489e0 R08: ffff88840d6e30f8 R09: 0000000000000000
<4> [201.320078] R10: 0000000000000000 R11: 0000000000000000 R12: ffffffff822d7bd1
<4> [201.320084] R13: ffffffff826489e0 R14: ffff88840f898300 R15: 0000000000000202
<4> [201.320091] FS:  0000000000000000(0000) GS:ffff88840f880000(0000) knlGS:0000000000000000
<4> [201.320098] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
<4> [201.320104] CR2: 0000000000000000 CR3: 0000000005610001 CR4: 00000000001606e0
<4> [201.320109] Call Trace:
<4> [201.320125]  __debug_object_init+0x359/0x510
<4> [201.320140]  ? _raw_spin_unlock_irqrestore+0x34/0x60
<4> [201.320156]  ? queue_work_node+0x70/0x70
<4> [201.320165]  init_timer_key+0x25/0x140
<4> [201.320180]  ? intel_thermal_supported+0x30/0x30
<4> [201.320191]  thermal_throttle_online+0xb4/0x260
<4> [201.320204]  ? unexpected_thermal_interrupt+0x20/0x20
<4> [201.320213]  cpuhp_invoke_callback+0x9b/0x9d0
<4> [201.320235]  cpuhp_thread_fun+0x1c8/0x220
<4> [201.320249]  ? smpboot_thread_fn+0x23/0x280
<4> [201.320259]  ? smpboot_thread_fn+0x6b/0x280
<4> [201.320271]  smpboot_thread_fn+0x1d3/0x280
<4> [201.320288]  ? sort_range+0x20/0x20
<4> [201.320295]  kthread+0x119/0x130
<4> [201.320303]  ? kthread_park+0x80/0x80
<4> [201.320317]  ret_from_fork+0x3a/0x50
<4> [201.320348] irq event stamp: 4846
<4> [201.320358] hardirqs last  enabled at (4845): [<ffffffff8112dcca>] console_unlock+0x4ba/0x5a0
<4> [201.320368] hardirqs last disabled at (4846): [<ffffffff81001ca0>] trace_hardirqs_off_thunk+0x1a/0x1c
<4> [201.320379] softirqs last  enabled at (4746): [<ffffffff81e00385>] __do_softirq+0x385/0x47f
<4> [201.320388] softirqs last disabled at (4739): [<ffffffff810ba15a>] irq_exit+0xba/0xc0
<4> [201.320394] ---[ end trace 06576bf31ad2ac2b ]---

Are we otherwise relying on current->nr_cpus_allowed == 1 here?
(As this section is not within a preempt_disable or local_irq_disable
region.)
-Chris