ports/151725: sysutils/hal: hald fails to start with dbus-1.4

[Andriy Gapon]

The following reply was made to PR ports/151725; it has been noted by GNATS.

From: Andriy Gapon <avg at freebsd.org>
To: Joe Marcus Clarke <marcus at freebsd.org>
Cc: Kevin Oberman <oberman at es.net>, gnome at freebsd.org,
        bug-followup at freebsd.org
Subject: Re: ports/151725: sysutils/hal: hald fails to start with dbus-1.4
Date: Tue, 09 Nov 2010 07:52:48 +0200

 on 09/11/2010 07:47 Joe Marcus Clarke said the following:
 > On 11/9/10 12:36 AM, Andriy Gapon wrote:
 >> on 09/11/2010 02:14 Kevin Oberman said the following:
 >>> I'll try this as soon as I can. I'm not too sure that it will happen as
 >>> I think that this is somehow timing related. I suspect that the entry is
 >>> disappearing too quickly with 1.4 in some cases but is not a problem
 >>> with 1.2. Perhaps some optimization? 
 >>>
 >>> I suggest this because on at least rare occasion, 1.4 did run
 >>> successfully, not because I have any clue what was happening under the
 >>> covers. 
 >>
 >> I guess that I already explained this part.
 >> The problem happened because we tried to write something (even if it's just zero
 >> sized something) into stdin of a child process that already exited.
 >> Sometimes the child process was quicker, sometimes the parent process was
 >> quicker, hence the non-determinism.
 >>
 > 
 > Ah, I missed that.  I wonder if it would be safer then to ignore SIGPIPE
 > around the write block.
 
 Maybe.  But not calling write(2) when we don't have anything to write (zero
 length) also looks like a good solution (for me personally).
 
 My point is: zero-sized write in nothing but testing OS implementation details
 of handling zero-sized writes, it doesn't perform any useful function.
 OTOH, if a child process is supposed to get any actual input, then it won't exit
 prematurely, but would block reading from its stdin until the input arrives.
 
 But I think I am starting to repeat what I have already wrote before.
 
 -- 
 Andriy Gapon