Re: Non-blocking read

Rogier Wolff (R.E.Wolff@BitWizard.nl)
Tue, 15 Jun 1999 07:25:17 +0200 (MEST)

Arjan van de Ven wrote:
> Hi,
>
> I want to do a non-blocking read from a file, from within the kernel.
> Is this, at all, possible? I have been tracing how userspace does this,
> but the userspace does not seem to be non-blocking either.
>
> What I'd expect is this:
>
> * non-blocking read is issued
> * if the pages are in the pagecache, they are copied to my buffer
> * if they are not, an asynchronous read-ahead is issued and the
> read-funtion returns -EAGAIN
>
> By looking at the code (2.3.6), there seems to be no possibility to do
> this. Am I wrong or is it not worth the effort (I might disagree) or just
> impossible?

Hi,

Yes, for the user-space issue, it was deemed not worth the
effort. Please disagree :-)

You also should make "select" work if you find the time to implement
it.

I think you should be able to issue a "read" request, and then not
go to sleep if you're in the kernel.

Roger.

-- 
** R.E.Wolff@BitWizard.nl ** http://www.BitWizard.nl/ ** +31-15-2137555 **
*-- BitWizard writes Linux device drivers for any device you may have! --*
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