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Date: Thu, 19 May 2016 17:35:02 -0500 (CDT)
From: Scot Doyle <lkml14@scotdoyle.com>
To: David Daney <ddaney.cavm@gmail.com>
cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Jiri Slaby <jslaby@suse.com>, Peter Hurley <peter@hurleysoftware.com>,
        Ming Lei <ming.lei@canonical.com>,
        Dann Frazier <dann.frazier@canonical.com>,
        Scot Doyle <lkml14@scotdoyle.com>, David Airlie <airlied@linux.ie>,
        dri-devel@lists.freedesktop.org, Radha.Chintakuntla@caviumnetworks.com,
        Pavel Machek <pavel@ucw.cz>, linux-kernel@vger.kernel.org,
        David Daney <david.daney@cavium.com>, stable@vger.kernel.org
Subject: Re: [PATCH] tty: vt: Fix soft lockup in fbcon cursor blink timer.
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On Tue, 17 May 2016, David Daney wrote:
> From: David Daney <david.daney@cavium.com>
> 
> We are getting somewhat random soft lockups with this signature:
> 
> [   86.992215] [<fffffc00080935e0>] el1_irq+0xa0/0x10c
> [   86.997082] [<fffffc000841822c>] cursor_timer_handler+0x30/0x54
> [   87.002991] [<fffffc000810ec44>] call_timer_fn+0x54/0x1a8
> [   87.008378] [<fffffc000810ef88>] run_timer_softirq+0x1c4/0x2bc
> [   87.014200] [<fffffc000809077c>] __do_softirq+0x114/0x344
> [   87.019590] [<fffffc00080af45c>] irq_exit+0x74/0x98
> [   87.024458] [<fffffc00080fac20>] __handle_domain_irq+0x98/0xfc
> [   87.030278] [<fffffc000809056c>] gic_handle_irq+0x94/0x190
> 
> This is caused by the vt visual_init() function calling into
> fbcon_init() with a vc_cur_blink_ms value of zero.  This is a
> transient condition, as it is later set to a non-zero value.  But, if
> the timer happens to expire while the blink rate is zero, it goes into
> an endless loop, and we get soft lockup.
> 
> The fix is to initialize vc_cur_blink_ms before calling the con_init()
> function.
> 
> Signed-off-by: David Daney <david.daney@cavium.com>
> Cc: stable@vger.kernel.org

Acked-by: Scot Doyle <lkml14@scotdoyle.com>