From: "H. Peter Anvin" <hpa@zytor.com>
To: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Christoph Lameter <cl@linux.com>, Tejun Heo <tj@kernel.org>,
Pekka Enbeerg <penberg@cs.helsinki.fi>,
linux-kernel@vger.kernel.org,
Eric Dumazet <eric.dumazet@gmail.com>,
Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Subject: Re: x86: A fast way to check capabilities of the current cpu
Date: Wed, 15 Dec 2010 13:39:12 -0800 [thread overview]
Message-ID: <4D093580.9000303@zytor.com> (raw)
In-Reply-To: <AANLkTimhdmWGhxW9qnFWYxiVDManH4XG4RqTLJb_Fdbk@mail.gmail.com>
On 12/15/2010 01:30 PM, Miguel Ojeda wrote:
>
> In this case it this_cpu_*_test_bit() return an int, but they act as a
> bool and are used in if()s; where is the catch?
>
If they aren't, and are stored in a variable for whatever reason, then
the || form will generate additional instructions to booleanize the
value for no good reason.
-hpa
next prev parent reply other threads:[~2010-12-15 21:40 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-12-15 20:07 x86: A fast way to check capabilities of the current cpu Christoph Lameter
2010-12-15 20:11 ` x86: Avoid passing struct cpuinfo pointer to mce_available Christoph Lameter
2010-12-15 20:56 ` x86: A fast way to check capabilities of the current cpu Andrew Morton
2010-12-15 21:03 ` H. Peter Anvin
2010-12-15 21:30 ` Miguel Ojeda
2010-12-15 21:39 ` H. Peter Anvin [this message]
2010-12-15 21:48 ` Miguel Ojeda
2010-12-16 6:25 ` Miles Bader
2010-12-16 10:17 ` Miguel Ojeda
2010-12-16 10:29 ` Miles Bader
2010-12-16 15:38 ` H. Peter Anvin
2010-12-17 4:26 ` Miles Bader
2011-01-21 17:11 ` Tejun Heo
2011-01-21 17:21 ` Christoph Lameter
2011-01-21 17:28 ` Tejun Heo
2011-01-21 17:46 ` Christoph Lameter
2011-01-21 17:48 ` Tejun Heo
2011-01-21 17:57 ` Christoph Lameter
2011-01-21 18:12 ` Tejun Heo
2011-01-21 18:20 ` Christoph Lameter
2011-01-21 22:32 ` H. Peter Anvin
2011-01-24 17:05 ` Christoph Lameter
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