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[MIT-Scheme-devel] pclsr


From: Taylor R Campbell
Subject: [MIT-Scheme-devel] pclsr
Date: Mon, 14 Mar 2011 22:15:36 +0000
User-agent: IMAIL/1.21; Edwin/3.116; MIT-Scheme/9.0.1

If I (open-output-file "/an/sshfs/on/a/distant/host"), Scheme spins.
This is frustrating.  (Edwin is still responsive, and I can still ^G
my way out of it, but Scheme never opens the file.)

This happens because

(a) the open(2) system call on sshfs takes longer to return than the
next Scheme thread timer interrupt takes to arrive, and

(b) the open(2) system call, like every Unix system call, backs out
instead of pclsring, so it loses any progress it might have made.

Blocking signals during open(2) would make it succeed in this case --
eventually.  However, it would have unacceptable consequences: trying
to open both ends of a fifo would permanently wedge Scheme; Edwin
would become unresponsive while you try to open remote files; &c.

Any ideas?



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