[libvirt] mingw: test-poll pipe part fails

Bastien ROUCARIES roucaries.bastien at gmail.com
Tue Jul 19 16:54:51 UTC 2011

I have some code if you want that work. If you could test, I wil lsend
you. I have no time to create m4 and proper gnulib integration. It is
up to you


On Tue, Jul 19, 2011 at 5:44 PM, Daniel P. Berrange <berrange at redhat.com> wrote:
> On Tue, Jul 19, 2011 at 09:31:59AM -0600, Eric Blake wrote:
>> On 07/19/2011 09:30 AM, Daniel P. Berrange wrote:
>> >>I'm wondering if the problem here is that libvirt is trying to use the
>> >>pipe-to-self mechanism as a fundamental event loop idiom.  That is, the
>> >>reason libvirt is calling poll is in order to minimize CPU until
>> >>something interesting happens, where interesting includes needing to
>> >>wake up a helper thread to do an action inside locks in response to the
>> >>receipt of a signal.
>> >>
>> >>Maybe you are on to something, and replacing all uses of pipe() with
>> >>virPipeToSelf() (which uses pipe() for efficiency on Linux, but
>> >>socketpair() on mingw), would allow libvirt to continue to use the
>> >>pipe-to-self idiom while also using fds that can actually be poll'd on
>> >>mingw.
>> >
>> >IIRC, we never resolved this for the last release. I think we should
>> >do as you suggest and just use socketpair() on Win32. Given the way
>> >in which libvirt uses these capabilities, I don't think the overheads
>> >of socketpair() vs pipe() are so onerous that we need worry about an
>> >even more fancy Win32 impl or eventfd for linux. Of course if someone
>> >wants todo a full job for gnulib meawhile, we won't complain...
>> Well, right now, we don't even have socketpair() for Win32.  We'd
>> have to wire up some other native APIs for this to work.
> Oh I read your mail above as indicating we did have socketpair()
> on Mingw32. A quick look through google, suggests most people
> go down the route of creating a TCP socket bound to localhost
> for this purpose.
> Daniel
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