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From:   Saravana Kannan <saravanak@google.com>
Date:   Mon, 2 Dec 2019 13:19:22 -0800
Message-ID: <CAGETcx9r0u=-WSnQ2ZS1KmZSVQqKwvpnhO-w41=jk8iF6BdALA@mail.gmail.com>
Subject: Re: 5e6669387e ("of/platform: Pause/resume sync state during init
 .."): [ 3.192726] WARNING: CPU: 1 PID: 1 at drivers/base/core.c:688 device_links_supplier_sync_state_resume
To:     Frank Rowand <frowand.list@gmail.com>,
        Rob Herring <robh+dt@kernel.org>
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@vger.kernel.org>, LKML <linux-kernel@vger.kernel.org>,
        LKP <lkp@lists.01.org>, kernel test robot <lkp@intel.com>
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Sender: linux-kernel-owner@vger.kernel.org
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On Sun, Dec 1, 2019 at 7:00 AM kernel test robot <lkp@intel.com> wrote:
>
> Greetings,
>
> 0day kernel testing robot got the below dmesg and the first bad commit is
>
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
>
> commit 5e6669387e2287f25f09fd0abd279dae104cfa7e
> Author:     Saravana Kannan <saravanak@google.com>
> AuthorDate: Wed Sep 4 14:11:24 2019 -0700
> Commit:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> CommitDate: Fri Oct 4 17:30:19 2019 +0200
>
>     of/platform: Pause/resume sync state during init and of_platform_populate()
>
>     When all the top level devices are populated from DT during kernel
>     init, the supplier devices could be added and probed before the
>     consumer devices are added and linked to the suppliers. To avoid the
>     sync_state() callback from being called prematurely, pause the
>     sync_state() callbacks before populating the devices and resume them
>     at late_initcall_sync().
>
>     Similarly, when children devices are populated from a module using
>     of_platform_populate(), there could be supplier-consumer dependencies
>     between the children devices that are populated. To avoid the same
>     problem with sync_state() being called prematurely, pause and resume
>     sync_state() callbacks across of_platform_populate().
>
>     Signed-off-by: Saravana Kannan <saravanak@google.com>
>     Link: https://lore.kernel.org/r/20190904211126.47518-6-saravanak@google.com
>     Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
>
> fc5a251d0f  driver core: Add sync_state driver/bus callback
> 5e6669387e  of/platform: Pause/resume sync state during init and of_platform_populate()
> 81b6b96475  Merge branch 'master' of git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux; tag 'dma-mapping-5.5' of git://git.infradead.org/users/hch/dma-mapping
> +-------------------------------------------------------------------------+------------+------------+------------+
> |                                                                         | fc5a251d0f | 5e6669387e | 81b6b96475 |
> +-------------------------------------------------------------------------+------------+------------+------------+
> | boot_successes                                                          | 30         | 0          | 0          |
> | boot_failures                                                           | 1          | 11         | 22         |
> | Oops:#[##]                                                              | 1          |            |            |
> | EIP:unmap_vmas                                                          | 1          |            |            |
> | PANIC:double_fault                                                      | 1          |            |            |
> | Kernel_panic-not_syncing:Fatal_exception                                | 1          |            |            |
> | WARNING:at_drivers/base/core.c:#device_links_supplier_sync_state_resume | 0          | 11         | 22         |
> | EIP:device_links_supplier_sync_state_resume                             | 0          | 11         | 22         |
> +-------------------------------------------------------------------------+------------+------------+------------+
>
> If you fix the issue, kindly add following tag
> Reported-by: kernel test robot <lkp@intel.com>
>
> [    3.186107] OF: /testcase-data/phandle-tests/consumer-b: #phandle-cells = 2 found -1
> [    3.188595] platform testcase-data:testcase-device2: IRQ index 0 not found
> [    3.191047] ### dt-test ### end of unittest - 199 passed, 0 failed
> [    3.191932] ------------[ cut here ]------------
> [    3.192571] Unmatched sync_state pause/resume!
> [    3.192726] WARNING: CPU: 1 PID: 1 at drivers/base/core.c:688 device_links_supplier_sync_state_resume+0x27/0xc0
> [    3.195084] Modules linked in:
> [    3.195494] CPU: 1 PID: 1 Comm: swapper/0 Tainted: G                T 5.4.0-rc1-00005-g5e6669387e228 #1
> [    3.196674] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1 04/01/2014
> [    3.197693] EIP: device_links_supplier_sync_state_resume+0x27/0xc0
> [    3.198680] Code: 00 00 00 3e 8d 74 26 00 57 56 31 d2 53 b8 a0 d0 d9 c1 e8 6c b6 38 00 a1 e4 d0 d9 c1 85 c0 75 13 68 84 ba c4 c1 e8 29 30 b1 ff <0f> 0b 58 eb 7f 8d 74 26 00 83 e8 01 85 c0 a3 e4 d0 d9 c1 75 6f 8b
> [    3.201560] EAX: 00000022 EBX: 00000000 ECX: 00000000 EDX: 00000000
> [    3.202466] ESI: 000001ab EDI: c02c7f80 EBP: c1e87d27 ESP: c02c7f20
> [    3.203301] DS: 007b ES: 007b FS: 00d8 GS: 0000 SS: 0068 EFLAGS: 00010282
> [    3.204258] CR0: 80050033 CR2: bfa1bf98 CR3: 01f28000 CR4: 00140690
> [    3.205022] DR0: 00000000 DR1: 00000000 DR2: 00000000 DR3: 00000000
> [    3.205919] DR6: fffe0ff0 DR7: 00000400
> [    3.206529] Call Trace:
> [    3.207011]  ? of_platform_sync_state_init+0x13/0x16
> [    3.207719]  ? do_one_initcall+0xda/0x260
> [    3.208247]  ? kernel_init_freeable+0x110/0x197
> [    3.208906]  ? rest_init+0x120/0x120
> [    3.209369]  ? kernel_init+0xa/0x100
> [    3.209775]  ? ret_from_fork+0x19/0x24
> [    3.210283] ---[ end trace 81d0f2d2ee65199b ]---
> [    3.210955] ALSA device list:

Rob/Frank,

This seems to be an issue with the unit test code not properly
cleaning up the state after it's done.

Specifically, unittest_data_add() setting up of_root on systems where
there's no device tree (of_root == NULL). It doesn't clean up of_root
after the tests are done. This affects the of_have_populated_dt() API
that in turn affects calls to
device_links_supplier_sync_state_pause/resume(). I think unittests
shouldn't affect the of_have_populated_dt() API.

I was looking into writing a unittest patch to fix this, but I don't
know enough about the FDT parsing code to make sure I don't leak any
memory or free stuff that's in use. I'm not sure I can simply set
of_root = NULL if it was NULL before the unittest started. Let me know
how I should proceed or if you plan to write up a patch for this.

Thanks,
Saravana