From: "H. Peter Anvin" <hpa@linux.intel.com>
To: "Pan, Jacob jun" <jacob.jun.pan@intel.com>
Cc: Pavel Machek <pavel@ucw.cz>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 2/9] x86: introduce a set of platform feature flags
Date: Thu, 02 Jul 2009 16:25:38 -0700 [thread overview]
Message-ID: <4A4D41F2.8070507@linux.intel.com> (raw)
In-Reply-To: <43F901BD926A4E43B106BF17856F07556428B555@orsmsx508.amr.corp.intel.com>
Pan, Jacob jun wrote:
>>> +#define platform_has(bit) \
>>> + test_bit(bit, (unsigned long *)platform_feature)
>> test_bit and friends imply synchronization you probably don't want or
>> need...
>>
> [[JPAN]] could you explain a little more? The disassembly shows the test_bit
> ends up as a testb instruction and a jump. Why there is synchronization
> involved?
> Perhaps on some architectures?
test_bit() doesn't imply synchronization; set_bit() and clear_bit() do
(but not __set_bit() and __clear_bit(), just to really be confusing.)
-hpa
prev parent reply other threads:[~2009-07-02 23:25 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-06-26 0:14 [PATCH 2/9] x86: introduce a set of platform feature flags Pan, Jacob jun
2009-06-26 7:22 ` Ingo Molnar
2009-06-26 9:14 ` Alan Cox
2009-06-26 9:45 ` Ingo Molnar
2009-06-26 10:17 ` Alan Cox
2009-06-26 10:47 ` Ingo Molnar
2009-06-26 11:41 ` Alan Cox
2009-06-26 15:47 ` Ingo Molnar
2009-06-26 19:04 ` H. Peter Anvin
2009-06-26 19:13 ` Ingo Molnar
2009-06-30 6:32 ` Pavel Machek
2009-07-02 23:09 ` Pan, Jacob jun
2009-07-02 23:25 ` H. Peter Anvin [this message]
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