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Subject: Re: [4.2.0-rc1-00201-g59c3cb5] Regression: kernel NULL pointer dereference
From: =?UTF-8?Q?J=C3=B6rg_Otte?= <jrg.otte@gmail.com>
To: David Airlie <airlied@linux.ie>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Daniel Vetter <daniel.vetter@ffwll.ch>,
        dri-devel@lists.freedesktop.org,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Ander Conselvan de Oliveira 
	<ander.conselvan.de.oliveira@intel.com>
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2015-07-12 10:03 GMT+02:00 Jörg Otte <jrg.otte@gmail.com>:
> 4.2.0-rc1-00201-g59c3cb5 introducued a null pointer derefence and a
> system freeze
> when Xorg is started ( 4.2.0-rc1-00062-gc4b5fd3 was fine) :
>
> BUG: unable to handle kernel NULL pointer dereference at 0000000000000009
> IP: [<ffffffffbd3447bb>] 0xffffffffbd3447bb
> PGD 0
> Oops: 0000 [#1] SMP
> CPU: 1 PID: 1290 Comm: Xorg Not tainted 4.2.0-rc1-00201-g59c3cb5 #6
> Hardware name: FUJITSU LIFEBOOK AH532/FJNBB1C, BIOS Version 1.09 05/22/2012
> task: ffff8802149d6c00 ti: ffff880206df4000 task.ti: ffff880206df4000
> RIP: 0010:[<ffffffffbd3447bb>]  [<ffffffffbd3447bb>] 0xffffffffbd3447bb
> RSP: 0018:ffff880206df7b08  EFLAGS: 00010246
> RAX: 0000000000000000 RBX: ffff88021578f480 RCX: ffff88021578f4d0
> RDX: 0000000000000000 RSI: ffff88021630b000 RDI: ffff880214a68000
> RBP: ffff88021630b000 R08: ffff88021578f4e0 R09: ffff88021578f4f0
> R10: 0000000000003c18 R11: 00000000fffffff2 R12: ffff880214a68000
> R13: ffff88021634e800 R14: 0000000000000000 R15: 0000000000000000
> FS:  00007ff3caa60880(0000) GS:ffff88021f280000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 0000000000000009 CR3: 0000000206e07000 CR4: 00000000001407e0
> Stack:
>  ffff880200010000 ffff880200010000 ffff880200000000 ffff880200000001
>  ffff88021578f500 ffffffffbd2df135 ffff880213f71c00 ffff880214a68000
>  0000000000000000 ffff880214a70000 0000000000000001 ffff880214a68000
> Call Trace:
>  [<ffffffffbd2df135>] ? 0xffffffffbd2df135
>  [<ffffffffbd2b6ca8>] ? 0xffffffffbd2b6ca8
>  [<ffffffffbd33cc7e>] ? 0xffffffffbd33cc7e
>  [<ffffffffbd343673>] ? 0xffffffffbd343673
>  [<ffffffffbd2d0728>] ? 0xffffffffbd2d0728
>  [<ffffffffbd2d088e>] ? 0xffffffffbd2d088e
>  [<ffffffffbd2d10c5>] ? 0xffffffffbd2d10c5
>  [<ffffffffbd2c6976>] ? 0xffffffffbd2c6976
>  [<ffffffffbd2d0fe0>] ? 0xffffffffbd2d0fe0
>  [<ffffffffbd0c6a1f>] ? 0xffffffffbd0c6a1f
>  [<ffffffffbd0e79e1>] ? 0xffffffffbd0e79e1
>  [<ffffffffbd0e7ed1>] ? 0xffffffffbd0e7ed1
>  [<ffffffffbd6df557>] ? 0xffffffffbd6df557
> Code: 48 89 54 24 20 48 8b 54 24 40 48 89 ee 89 0c 24 4c 89 f9 c7 44
> 24 18 01 00 00 00 89 44 24 08 e8 bc 1f f7 ff 85 c0 41 89 c7 75 67 <41>
> 80 7e 09 00 74 56 49 8b 84 24 38 02 00 00 c6 85 d0 08 00 00
> RIP  [<ffffffffbd3447bb>] 0xffffffffbd3447bb
>  RSP <ffff880206df7b08>
> CR2: 0000000000000009
> ---[ end trace dd0931f7f0d43d12 ] ---

I can fix the problem for me by reverting:

commit dec4f799d0a4c9edae20512fa60b0a36f3299ca2
Author: Daniel Vetter <daniel.vetter@ffwll.ch>
Date:   Tue Jul 7 11:15:47 2015 +0200

    drm/i915: Use crtc_state->active in primary check_plane func
    Since
    commit 8c7b5ccb729870e606321b3703e2c2e698c49a95
    Author: Ander Conselvan de Oliveira <ander.conselvan.de.oliveira@intel.com>
    Date:   Tue Apr 21 17:13:19 2015 +0300
    drm/i915: Use atomic helpers for computing changed flags

Thanks, Jörg
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