From mboxrd@z Thu Jan  1 00:00:00 1970
From: Jeff King <peff@peff.net>
Subject: Re: [PATCH 3/8] xread_nonblock: add functionality to read from fds
 without blocking
Date: Mon, 14 Dec 2015 18:57:37 -0500
Message-ID: <20151214235736.GA26133@sigill.intra.peff.net>
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Cc: Eric Sunshine <ericsunshine@gmail.com>,
	Stefan Beller <sbeller@google.com>,
	Git List <git@vger.kernel.org>,
	Jonathan Nieder <jrnieder@gmail.com>,
	Johannes Schindelin <johannes.schindelin@gmail.com>,
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To: Junio C Hamano <gitster@pobox.com>
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On Mon, Dec 14, 2015 at 03:15:29PM -0800, Junio C Hamano wrote:

> -- >8 --
> From: Stefan Beller <sbeller@google.com>
> Date: Mon, 14 Dec 2015 11:37:13 -0800
> Subject: [PATCH] xread_nonblock: add functionality to read from fds without blocking
> 
> Provide a wrapper to read(), similar to xread(), that restarts on
> EINTR but not EAGAIN (or EWOULDBLOCK). This enables the caller to
> handle polling itself, possibly polling multiple sockets or performing
> some other action.

This makes me wonder why we restart xread() on EAGAIN in the first
place.

On EINTR, sure; signals can come and we want to keep going. But if do
not have non-blocking descriptors, it should never happen, right?

Are we trying to protect ourselves against somebody _else_ giving us a
non-blocking descriptor? In that case we'll quietly spin and waste CPU.
Which isn't great, but perhaps better than returning an error.

-Peff