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Message-Id: <alpine.LFD.2.20.1707241441120.9422@schleppi>
Date:   Mon, 24 Jul 2017 14:46:23 +0200 (CEST)
From:   Sebastian Ott <sebott@...ux.vnet.ibm.com>
To:     Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
cc:     Petr Mladek <pmladek@...e.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Michal Hocko <mhocko@...nel.org>,
        Heiko Carstens <heiko.carstens@...ibm.com>,
        Martin Schwidefsky <schwidefsky@...ibm.com>,
        linux-kernel@...r.kernel.org,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>
Subject: Re: lockdep warning: console vs. mem hotplug

Hello Sergey,

On Tue, 21 Mar 2017, Sergey Senozhatsky wrote:
> // I kept only lockdep splats from the original report and cut off .configs
> // full version:
> // lkml.kernel.org/r/alpine.LFD.2.20.1703201736070.1753@...leppi
>
> On (03/20/17 17:43), Sebastian Ott wrote:
> > Since commit f975237b7682 ("printk: use printk_safe buffers in printk")
> > I observe lockdep warnings on s390 when doing memory hotplug:

When using the sclp console I can no longer recreate that lockdep warning
but the other one is still present:

[  347.644660] ======================================================
[  347.644660] WARNING: possible circular locking dependency detected
[  347.644661] 4.13.0-rc2 #146 Not tainted
[  347.644661] ------------------------------------------------------
[  347.644662] sh/770 is trying to acquire lock:
[  347.644662]  (&console_sch_key){-.-...}, at: [<0000000000763d80>] raw3215_write+0x58/0x208
[  347.644665] but task is already holding lock:
[  347.644665]  (&(&zone->lock)->rlock){-.-...}, at: [<00000000002b693e>] __offline_isolated_pages+0x316/0x388
[  347.644668] which lock already depends on the new lock.
[  347.644669] the existing dependency chain (in reverse order) is:
[  347.644670] -> #4 (&(&zone->lock)->rlock){-.-...}:
[  347.644672]        validate_chain.isra.10+0xb56/0xd88
[  347.644673]        __lock_acquire+0x62c/0x850
[  347.644673]        lock_acquire+0x254/0x2b8
[  347.644674]        _raw_spin_lock_irqsave+0x70/0xb8
[  347.644674]        get_page_from_freelist+0x446/0xf30
[  347.644675]        __alloc_pages_nodemask+0x200/0x1568
[  347.644675]        allocate_slab+0xf0/0x658
[  347.644676]        new_slab+0x94/0xa8
[  347.644677]        ___slab_alloc.constprop.23+0x55e/0x580
[  347.644677]        __slab_alloc.isra.17.constprop.22+0x74/0xa8
[  347.644678]        kmem_cache_alloc+0x13c/0x4b0
[  347.644678]        __debug_object_init+0x5c/0x468
[  347.644679]        hrtimer_init+0x42/0x1d8
[  347.644679]        init_dl_task_timer+0x3a/0x58
[  347.644680]        __sched_fork.isra.2+0x82/0xd8
[  347.644680]        init_idle+0x7a/0x278
[  347.644681]        fork_idle+0xa4/0xb8
[  347.644681]        idle_threads_init+0x6a/0xd0
[  347.644682]        smp_init+0x34/0x110
[  347.644682]        kernel_init_freeable+0x166/0x2d8
[  347.644683]        kernel_init+0x2a/0x148
[  347.644683]        kernel_thread_starter+0x6/0xc
[  347.644684]        kernel_thread_starter+0x0/0xc

[  347.644684] -> #3 (&rq->lock){-.-.-.}:
[  347.644686]        validate_chain.isra.10+0xb56/0xd88
[  347.644687]        __lock_acquire+0x62c/0x850
[  347.644687]        lock_acquire+0x254/0x2b8
[  347.644688]        _raw_spin_lock+0x60/0xa0
[  347.644688]        task_fork_fair+0x6a/0x160
[  347.644689]        sched_fork+0x13e/0x2a0
[  347.644689]        copy_process+0x676/0x1ec0
[  347.644690]        _do_fork+0xc2/0x6d0
[  347.644690]        kernel_thread+0x4e/0x60
[  347.644691]        rest_init+0x48/0x290
[  347.644691]        start_kernel+0x470/0x480
[  347.644692]        _stext+0x20/0x80

[  347.644693] -> #2 (&p->pi_lock){-.-.-.}:
[  347.644695]        validate_chain.isra.10+0xb56/0xd88
[  347.644695]        __lock_acquire+0x62c/0x850
[  347.644696]        lock_acquire+0x254/0x2b8
[  347.644696]        _raw_spin_lock_irqsave+0x70/0xb8
[  347.644697]        try_to_wake_up+0x4a/0x600
[  347.644697]        autoremove_wake_function+0x2e/0x88
[  347.644698]        __wake_up_common+0x76/0xc0
[  347.644698]        __wake_up+0x54/0x68
[  347.644699]        ccw_device_verify_done+0xae/0x268
[  347.644700]        ccw_request_handler+0x422/0x560
[  347.644700]        do_cio_interrupt+0x224/0x2a0
[  347.644701]        __handle_irq_event_percpu+0x1a6/0x440
[  347.644701]        handle_irq_event_percpu+0x38/0x88
[  347.644702]        handle_percpu_irq+0x84/0xb0
[  347.644702]        generic_handle_irq+0x42/0x60
[  347.644703]        do_IRQ+0x86/0xc8
[  347.644703]        io_int_handler+0x104/0x2d4
[  347.644704]        enabled_wait+0x72/0x140
[  347.644704]        enabled_wait+0x5a/0x140
[  347.644705]        arch_cpu_idle+0x32/0x50
[  347.644706]        default_idle_call+0x52/0x68
[  347.644706]        do_idle+0x118/0x170
[  347.644707]        cpu_startup_entry+0x3e/0x48
[  347.644707]        smp_start_secondary+0x112/0x120
[  347.644708]        restart_int_handler+0x62/0x78
[  347.644708]                  (null)

[  347.644709] -> #1 (&priv->wait_q){-.....}:
[  347.644711]        validate_chain.isra.10+0xb56/0xd88
[  347.644711]        __lock_acquire+0x62c/0x850
[  347.644712]        lock_acquire+0x254/0x2b8
[  347.644712]        _raw_spin_lock_irqsave+0x70/0xb8
[  347.644713]        __wake_up+0x3a/0x68
[  347.644713]        ccw_device_recog_done+0x28e/0x2c8
[  347.644714]        snsid_callback+0x324/0x390
[  347.644714]        ccw_request_handler+0x480/0x560
[  347.644715]        do_cio_interrupt+0x224/0x2a0
[  347.644715]        __handle_irq_event_percpu+0x1a6/0x440
[  347.644715]        handle_irq_event_percpu+0x38/0x88
[  347.644716]        handle_percpu_irq+0x84/0xb0
[  347.644716]        generic_handle_irq+0x42/0x60
[  347.644717]        do_IRQ+0x86/0xc8
[  347.644717]        io_int_handler+0x104/0x2d4
[  347.644718]        _raw_spin_unlock_irq+0x4e/0x78
[  347.644718]        _raw_spin_unlock_irq+0x4a/0x78
[  347.644719]        ccw_device_enable_console+0xa0/0x188
[  347.644719]        con3215_init+0x116/0x1b8
[  347.644720]        console_init+0x40/0x60
[  347.644720]        start_kernel+0x34c/0x480
[  347.644720]        _stext+0x20/0x80

[  347.644721] -> #0 (&console_sch_key){-.-...}:
[  347.644723]        check_prev_add+0x160/0x6e8
[  347.644723]        validate_chain.isra.10+0xb56/0xd88
[  347.644723]        __lock_acquire+0x62c/0x850
[  347.644724]        lock_acquire+0x254/0x2b8
[  347.644724]        _raw_spin_lock_irqsave+0x70/0xb8
[  347.644725]        raw3215_write+0x58/0x208
[  347.644725]        con3215_write+0x8e/0xf8
[  347.644725]        console_unlock+0x4d8/0x6a8
[  347.644726]        vprintk_emit+0x308/0x378
[  347.644726]        vprintk_default+0x44/0x58
[  347.644727]        printk+0x4e/0x60
[  347.644727]        __offline_isolated_pages+0x16a/0x388
[  347.644728]        offline_isolated_pages_cb+0x2e/0x40
[  347.644728]        walk_system_ram_range+0x92/0xf0
[  347.644729]        __offline_pages.constprop.6+0x6d2/0x910
[  347.644729]        memory_subsys_offline+0x6c/0xa0
[  347.644730]        device_offline+0x84/0xe0
[  347.644730]        store_mem_state+0xfe/0x120
[  347.644731]        kernfs_fop_write+0x132/0x208
[  347.644731]        __vfs_write+0x36/0x158
[  347.644731]        vfs_write+0xb8/0x1a0
[  347.644732]        SyS_write+0x66/0xc0
[  347.644732]        system_call+0xc4/0x298
[  347.644733] other info that might help us debug this:
[  347.644734] Chain exists of:
[  347.644734]   &console_sch_key --> &rq->lock --> &(&zone->lock)->rlock
[  347.644736]  Possible unsafe locking scenario:
[  347.644737]        CPU0                    CPU1
[  347.644738]        ----                    ----
[  347.644738]   lock(&(&zone->lock)->rlock);
[  347.644739]                                lock(&rq->lock);
[  347.644740]                                lock(&(&zone->lock)->rlock);
[  347.644741]   lock(&console_sch_key);
[  347.644742]  *** DEADLOCK ***
[  347.644743] 9 locks held by sh/770:
[  347.644743]  #0:  (sb_writers#5){.+.+.+}, at: [<000000000035c64a>] vfs_write+0xa2/0x1a0
[  347.644745]  #1:  (&of->mutex){+.+.+.}, at: [<000000000040065a>] kernfs_fop_write+0x1b2/0x208
[  347.644747]  #2:  (s_active#46){.+.+.+}, at: [<0000000000400666>] kernfs_fop_write+0x1be/0x208
[  347.644749]  #3:  (device_hotplug_lock){+.+...}, at: [<00000000006b9d18>] lock_device_hotplug_sysfs+0x30/0x70
[  347.644750]  #4:  (cpu_hotplug_lock.rw_sem){++++++}, at: [<000000000033596a>] mem_hotplug_begin+0x2a/0x40
[  347.644752]  #5:  (mem_hotplug_lock.rw_sem){++++.+}, at: [<00000000001a5c78>] percpu_down_write+0x38/0x110
[  347.644754]  #6:  (&dev->mutex){......}, at: [<00000000006bb5ac>] device_offline+0x5c/0xe0
[  347.644756]  #7:  (&(&zone->lock)->rlock){-.-...}, at: [<00000000002b693e>] __offline_isolated_pages+0x316/0x388
[  347.644758]  #8:  (console_lock){+.+...}, at: [<00000000001c2a3c>] vprintk_emit+0x2fc/0x378
[  347.644760] stack backtrace:
[  347.644760] CPU: 2 PID: 770 Comm: sh Not tainted 4.13.0-rc2 #146
[  347.644761] Hardware name: IBM 2827 H66 706 (z/VM 6.3.0)
[  347.644761] Call Trace:
[  347.644761] ([<0000000000113a1a>] show_stack+0x8a/0xe0)
[  347.644762]  [<00000000008fe4a6>] dump_stack+0x96/0xd8 
[  347.644762]  [<00000000001a95c4>] print_circular_bug+0x314/0x340 
[  347.644763]  [<00000000001aa548>] check_prev_add+0x160/0x6e8 
[  347.644763]  [<00000000001ab626>] validate_chain.isra.10+0xb56/0xd88 
[  347.644764]  [<00000000001ad024>] __lock_acquire+0x62c/0x850 
[  347.644764]  [<00000000001adbec>] lock_acquire+0x254/0x2b8 
[  347.644765]  [<000000000091e4a8>] _raw_spin_lock_irqsave+0x70/0xb8 
[  347.644766]  [<0000000000763d80>] raw3215_write+0x58/0x208 
[  347.644766]  [<000000000076416e>] con3215_write+0x8e/0xf8 
[  347.644766]  [<00000000001c2570>] console_unlock+0x4d8/0x6a8 
[  347.644767]  [<00000000001c2a48>] vprintk_emit+0x308/0x378 
[  347.644767]  [<00000000001c2c94>] vprintk_default+0x44/0x58 
[  347.644768]  [<00000000001c3c0e>] printk+0x4e/0x60 
[  347.644768]  [<00000000002b6792>] __offline_isolated_pages+0x16a/0x388 
[  347.644769]  [<0000000000335516>] offline_isolated_pages_cb+0x2e/0x40 
[  347.644769]  [<000000000014b092>] walk_system_ram_range+0x92/0xf0 
[  347.644770]  [<0000000000913cfa>] __offline_pages.constprop.6+0x6d2/0x910 
[  347.644770]  [<00000000006d8cf4>] memory_subsys_offline+0x6c/0xa0 
[  347.644771]  [<00000000006bb5d4>] device_offline+0x84/0xe0 
[  347.644771]  [<00000000006d93de>] store_mem_state+0xfe/0x120 
[  347.644772]  [<00000000004005da>] kernfs_fop_write+0x132/0x208 
[  347.644773]  [<000000000035b236>] __vfs_write+0x36/0x158 
[  347.644773]  [<000000000035c660>] vfs_write+0xb8/0x1a0 
[  347.644774]  [<000000000035dd96>] SyS_write+0x66/0xc0 
[  347.644774]  [<000000000091f59c>] system_call+0xc4/0x298 
[  347.644774] INFO: lockdep is turned off.

Sebastian

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