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deadlock in with fifo reading in tests/dd/

From: Pádraig Brady
Subject: deadlock in with fifo reading in tests/dd/
Date: Wed, 11 Dec 2013 05:15:02 +0000
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130110 Thunderbird/17.0.2

I noticed _once_ a deadlock in dd in tests/dd/
with make -j20 on a solaris 10 system.
Does anyone see why a dd process would deadlock here?;a=blob;f=tests/dd/;h=dd1a7408b

Now I haven't reproduced the deadlock, but I don't
immediately see why it should deadlock.

I see that the dd processes can go away without reading
due to the ulimit. But that would only cause multiple
`echo 1 > tape` instances to hang around which would
surely give less chance for subsequent dd processes to hang?

I considered adding a 'wait' after each (ulimit...)
but that could introduce a deadlock given the dd
process may go away even before the subshell opens the fifo,
especially for the `dd seek=1` case which can proceed
through an open(RDWR); malloc(large); and be killed even
before the background process blocks.

So I'll probably redo this test, or at least
mark it expensive so it's not run by default.


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