Re: [PATCH] http-backend: Don't infinite loop during die()

From: Shawn Pearce <spearce@spearce.org>
Date: Mar 24, 2010, 20:25 UTC
Message-ID: <ec874dac1003241325y43fdec78gfbb3d115e1aaa1b0@mail.gmail.com>
In-Reply-To: <alpine.LFD.2.00.1003241623370.694@xanadu.home>

On Wed, Mar 24, 2010 at 1:24 PM, Nicolas Pitre <nico@fluxnic.net> wrote:

Show 23 quoted lines

> On Wed, 24 Mar 2010, Shawn O. Pearce wrote:
>
>> Junio C Hamano <gitster@pobox.com> wrote:
>> > "Shawn O. Pearce" <spearce@spearce.org> writes:
>> >
>> > > If stdout has already been closed by the CGI and die() gets called,
>> > > the CGI will fail to write the "Status: 500 Internal Server Error" to
>> > > the pipe, which results in die() being called again (via safe_write).
>> > > This goes on in an infinite loop until the stack overflows and the
>> > > process is killed by SIGSEGV.
>> > >
>> > > Instead set a flag on the first die() invocation and perform no
>> > > action during recursive die() calls.  This way failures to write the
>> > > error messages to the stdout pipe do not result in an infinite loop.
>> >
>> > Hmm.  I would need something like this on top, but there must be a better
>> > way.  Ideas?
>>
>> Ick.
>>
>> Just exit(0) if dead is true.
>
> Do you really want the exit code to be 0 if you're dying?

IIRC, yes. If we exit non-zero Apache really freaked out. That was a big part of my motivation to write the die_webcgi handler.

-- 
Shawn.