From: Eric Wong <e@80x24.org>
Date: Sun, 26 Jun 2016 08:53:47 GMT
Subject: Re: [PATCH v12 04/20] index-helper: new daemon for caching index and related stuff
Message-ID: <20160626085347.GA4053@dcvr.yhbt.net>
In-Reply-To: <576ED9A2.8070202@novalis.org>

David Turner <novalis@novalis.org> wrote:
> On 06/25/2016 10:33 AM, Duy Nguyen wrote:
> >>+               /*
> >>+                * Our connection to the client is blocking since a client
> >>+                * can always be killed by SIGINT or similar.
> >>+                */
> >>+               set_socket_blocking_flag(client_fd, 0);
> >
> >Out of curiosity, do we really need this? I thought default behavior
> >was always blocking (and checked linux kernel, it seemed to agree with
> >me). Maybe for extra safety because other OSes may default to
> >something else?
> 
> Yes -- see this bug report for details:
> https://bugs.python.org/issue7995

I realize it's an issue with BSDs, but it still seems
unnecessary, here:

1) the packet_read => get_packet_data => read_in_full => xread
   call chain already poll()s on EAGAIN/EWOULDBLOCK.
   write_in_full => xwrite busy loops on EAGAIN/EWOULDBLOCK.
   xwrite should probably poll, too; but I guess EAGAIN is
   uncommon with small writes.

2) you create the listen fd you call accept on and never set
   non-blocking on it.  It might be an issue one day if
   we use socket activation and inherit a socket, but the
   retries mentioned in 1) should cover that case.