linux-kernel - Re: [PATCH] vgacon.c: add cond reschedule points in vgacon_do_font

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Date:	Wed, 26 Jun 2013 16:36:49 +1000
From:	Dave Airlie <airlied@...il.com>
To:	Marcelo Tosatti <mtosatti@...hat.com>
Cc:	Dave Airlie <airlied@...hat.com>, linux-kernel@...r.kernel.org,
	Gleb Natapov <gleb@...hat.com>,
	Paolo Bonzini <pbonzini@...hat.com>
Subject: Re: [PATCH] vgacon.c: add cond reschedule points in vgacon_do_font_op

> can result in a soft lockup:
>
> BUG: soft lockup - CPU#41 stuck for 67s! [setfont:1505]
>  RIP: 0010:[<ffffffff812c48da>]
> [<ffffffff812c48da>] vgacon_do_font_op.clone.0+0x1ba/0x550
>
> This is due to the 8192 (cmapsz) IO operations taking longer than expected
> due to lock contention in QEMU.
>
> Add conditional resched points in between writes allowing other tasks to
> execute.

I've applied this to drm-next against my best judgement as it steers
me close to being the console maintainer.

Dave.
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