linux-kernel - Re: select(0, ..) is valid ?

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Message-ID: <4649F11F.3040807@zytor.com>
Date:	Tue, 15 May 2007 10:42:55 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Badari Pulavarty <pbadari@...ibm.com>
CC:	netdev@...r.kernel.org, lkml <linux-kernel@...r.kernel.org>,
	Christoph Lameter <clameter@....com>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: select(0, ..) is valid ?

Badari Pulavarty wrote:
> Hi,
> 
> Is select(0, ..) is a valid operation ?
> 
> I see that there is no check to prevent this or return
> success early, without doing any work. Do we need one ?
> 
> slub code is complaining that we are doing kmalloc(0).
> 

select(0, ...) is valid, and is functionally equivalent to
select(..., NULL, NULL, NULL, ...); except that any nonzero fdsets get
zeroed on return.  As such, the only thing that can interrupt it is the
timeout, or a signal.

	-hpa
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