linux-kernel - Re: [PATCH 2/2] drm/i915: Limit the busy wait on requests to 2us not 10ms!

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Message-ID: <20151115174823.GP569@nuc-i3427.alporthouse.com>
Date:	Sun, 15 Nov 2015 17:48:23 +0000
From:	Chris Wilson <chris@...is-wilson.co.uk>
To:	Jens Axboe <axboe@...nel.dk>, intel-gfx@...ts.freedesktop.org,
	linux-kernel@...r.kernel.org
Cc:	dri-devel@...ts.freedesktop.org,
	Daniel Vetter <daniel.vetter@...ll.ch>,
	Tvrtko Ursulin <tvrtko.ursulin@...ux.intel.com>,
	Eero Tamminen <eero.t.tamminen@...el.com>,
	"Rantala, Valtteri" <valtteri.rantala@...el.com>,
	stable@...nel.vger.org
Subject: Re: [PATCH 2/2] drm/i915: Limit the busy wait on requests to 2us not
 10ms!

On Sun, Nov 15, 2015 at 01:32:44PM +0000, Chris Wilson wrote:
> +static bool busywait_stop(u64 timeout, unsigned cpu)
> +{
> +	unsigned this_cpu;
> +
> +	if (time_after64(local_clock_us(&this_cpu), timeout))
> +		return true;

Just a note to say that we can use the unsigned long version rather than
pass around u64 as this test will wraparound correctly (if we discard
the high bits on x86-32).
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre
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