Patchwork [2,of,2,V2] windows: allow readpipe() to actually read data out of the pipe

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Submitter Matt Harbison
Date April 8, 2015, 3:30 a.m.
Message ID <2a9f7b16b25b84bf814b.1428463842@Envy>
Download mbox | patch
Permalink /patch/8559/
State Accepted
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Matt Harbison - April 8, 2015, 3:30 a.m.
# HG changeset patch
# User Matt Harbison <matt_harbison@yahoo.com>
# Date 1428460296 14400
#      Tue Apr 07 22:31:36 2015 -0400
# Node ID 2a9f7b16b25b84bf814b953e26e3d4142c4b7722
# Parent  baeeb5f4bd5980f8722221156bbee3c3329c448b
windows: allow readpipe() to actually read data out of the pipe

It appears that the read() in readpipe() never actually ran before (in
test-ssh.t anyway).  A print of the size returned from os.fstat() is 0 for every
single print output in test-ssh.t, so the data in the pipe ends up being read
later instead of when it is available.  This is the same problem as Linux, as
mentioned in 331cbf088c4c.

There are several places in the Windows SSH tests where the order of local
output vs remote output differ from the other platforms.  This only fixes one of
those cases (and interstingly, not the one added in order to test 331cbf088c4c),
so there is more investigation needed.  However, without this patch, test-ssh.t
also has this diff:

    --- c:/Users/Matt/Projects/hg/tests/test-ssh.t
    +++ c:/Users/Matt/Projects/hg/tests/test-ssh.t.err
    @@ -397,11 +397,11 @@
       $ hg push --ssh "sh ../ssh.sh"
       pushing to ssh://user@dummy/*/remote (glob)
       searching for changes
    -  remote: Permission denied
    -  remote: abort: prechangegroup.hg-ssh hook failed
    -  remote: Permission denied
    -  remote: pushkey-abort: prepushkey.hg-ssh hook failed
       updating 6c0482d977a3 to public failed!
    +  remote: Permission denied
    +  remote: abort: prechangegroup.hg-ssh hook failed
    +  remote: Permission denied
    +  remote: pushkey-abort: prepushkey.hg-ssh hook failed
       [1]

       $ cd ..

Output with this change was stable over 600+ runs of test-ssh.t.  I initially
tried a background thread to read the pipe[1], but this was simpler and the test
results were exactly the same.  I also tried SetNamedPipeHandleState(), but the
PIPE_NOWAIT is for compatibility with LANMAN 2.0, not for async I/O (the results
were identical though).

[1] http://eyalarubas.com/python-subproc-nonblock.html
Matt Mackall - April 8, 2015, 6:53 p.m.
On Tue, 2015-04-07 at 23:30 -0400, Matt Harbison wrote:
> # HG changeset patch
> # User Matt Harbison <matt_harbison@yahoo.com>
> # Date 1428460296 14400
> #      Tue Apr 07 22:31:36 2015 -0400
> # Node ID 2a9f7b16b25b84bf814b953e26e3d4142c4b7722
> # Parent  baeeb5f4bd5980f8722221156bbee3c3329c448b
> windows: allow readpipe() to actually read data out of the pipe

These are queued for default, thanks (with nit fixed).

Patch

diff --git a/mercurial/windows.py b/mercurial/windows.py
--- a/mercurial/windows.py
+++ b/mercurial/windows.py
@@ -363,7 +363,7 @@ 
     """Read all available data from a pipe."""
     chunks = []
     while True:
-        size = os.fstat(pipe.fileno()).st_size
+        size = win32.peekpipe(pipe)
         if not size:
             break