On Sun, 4 Mar 2007, Divacky Roman wrote:
I looked at where Giant is held in the kernel and I found these interesting
things:
1) in fs/fifofs/fifo_vnops.c we lock Giant when calling sorecieve()/sosend()
this is a bandaid for fixing a race that doesnt have to exist anymore. ie.
it needs some testing and can be remvoed
Hmm. I think that conclusion is a bit premature. Per our conversation on
IRC, the workaround was added back prior to a release due to our being unable
to resolve a very difficult to debug race condition. There is no evidence the
race doesn't exist anymore: what is needed is testing to determine if it does
or not. The race condition occurred under high make -j load on SMP; FYI, make
uses a fifo to implement a concurrency limiting token scheme in order to bound
total simultaneous jobs despite many make instances running.
I've CC'd Kris since I know that he was able to reproduce the problem, so
might be able to provide advice on how to do so.
Robert N M Watson
Computer Laboratory
University of Cambridge
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