Date: Sat, 13 Dec 2014 22:10:18 -0500 (EST) From: Benjamin Kaduk <bjk@freebsd.org> To: Mateusz Guzik <mjguzik@gmail.com> Cc: "svn-src-head@freebsd.org" <svn-src-head@freebsd.org>, "svn-src-all@freebsd.org" <svn-src-all@freebsd.org>, "src-committers@freebsd.org" <src-committers@freebsd.org>, Chagin Dmitry <dchagin@freebsd.org> Subject: Re: svn commit: r275751 - in head: share/man/man9 sys/kern sys/sys Message-ID: <alpine.GSO.1.10.1412132206580.23489@multics.mit.edu> In-Reply-To: <20141213215011.GA17746@dft-labs.eu> References: <201412132100.sBDL0BvR094009@svn.freebsd.org> <CAJ5_RoCnMNEEa86besbhfKTxf-wOhwBy%2BjktLB7%2Bod=zkSQ6Aw@mail.gmail.com> <20141213213111.GA2070@dchagin.static.corbina.net> <20141213215011.GA17746@dft-labs.eu>
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On Sat, 13 Dec 2014, Mateusz Guzik wrote: > I think the actual question was when would you call _init_flags and not > want _NEW and it would have a potential to detect double init. That is a fine question to ask, but it is not the one I was trying to ask. I can answer yours, though: it detects when buggy code is using uninitialized memory for a structure that needs initialization. If I remember correctly, the need for https://github.com/openafs/openafs/commit/64da7c133a66a15233c2cdc5d9a8f71d17d80d77 was detected by this feature of WITNESS. > I think a better approach would be to have a hash with addresses of all > locks in use. Then _init/_destroy would add/remove it respectively and > we would not be dependent on the state of the lock (e.g. struct could be > zeroed by unrelated code and then double init is not detected). > > Chains locked separately of course. > > I didn't try that, should be totally fine for invariants. That is an interesting proposal, which might be better than the current state of affairs. (I am not signing up to implement it, though.) -Ben
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