On Aug 31 17:27, Corinna Vinschen wrote:
> On Aug 31 17:18, Corinna Vinschen wrote:
> > On Aug 31 08:33, Ken Brown wrote:
> > > On 8/31/2021 7:45 AM, Takashi Yano wrote:
> > > > On Tue, 31 Aug 2021 12:18:57 +0200
> > > > Corinna Vinschen wrote:
> > > > > Please try the attached patch on top of topic/pipe.
> > > > 
> > > > Thanks for the new patch. I have confirmed that above issue
> > > > is fixed and select() for write pipe seems to work as expected.
> > > > 
> > > > 
> > > > BTW, I found one minor difference between Linux and this pipe
> > > > implementation.
> > > > [...]
> > > > Is this difficult to be fixed?
> > > Two other remarks:
> > > 
> > > 1. I think query_hdl needs to be initialized in the fhandler_pipe constructor.
> > 
> > No, that's not necessary.  The fhandlers are always ccalloc'ed so they
> > are all 0 anyway.
> > 
> > > 2. When the read side of the pipe is non-blocking, there can be no pending
> > > reads, so shouldn't we be able to use WriteQuotaAvailable reliably on the
> > > write side?  (I can't test this at the moment.)
> > 
> > In theory, yes, but is it a safe bet that non-blocking reads won't change
> > WriteQuotaAvailable on the write side, at least for a very short time?
> > The question is, of course, if that really makes much of a difference.
> 
> Oh, btw... why do you want to use WriteQuotaAvailable for normal
> pipes, even though the read side information is available anyway?
> 
> We can do that for fifos, no problem, but it doesn't make much sense
> to differ between blocking and non-blocking pipes, the code flow is the
> same.

So for the time being I suggest the below patch on top of topic/pipe.
It contains everything we discussed so far.

One question left is, do we want to switch to FILE_PIPE_BYTE_STREAM_TYPE
entirely for pipes?  I don't see that it's still necessary to use
FILE_PIPE_MESSAGE_TYPE for pipes.  Everything seems to work normally
with byte-type pipes.