Date: Mon, 20 Oct 2003 15:10:53 -0500 From: Alan Cox <alc@cs.rice.edu> To: Scott Long <scottl@freebsd.org> Cc: cvs-src@FreeBSD.org Subject: Re: cvs commit: src/sys/dev/streams streams.c src/sys/kernkern_descrip.c kern_event.c sys_pipe.c uipc_syscalls.cvfs_syscalls.c src/sys/opencrypto cryptodev.c Message-ID: <20031020201053.GL20658@cs.rice.edu> In-Reply-To: <20031020135441.S50707@pooker.samsco.home> References: <200310200848.aa99929@salmon.maths.tcd.ie> <20031020095412.F49719@pooker.samsco.home> <20031020101425.H49719@pooker.samsco.home> <20031020135441.S50707@pooker.samsco.home>
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On Mon, Oct 20, 2003 at 01:58:08PM -0600, Scott Long wrote: > On Mon, 20 Oct 2003, Scott Long wrote: > > > > > > On Mon, 20 Oct 2003, Scott Long wrote: > > > > > On Mon, 20 Oct 2003, David Malone wrote: > > > > > > This reminds me that we still hold Giant around pipe(2) because it isn't > > > > > > declared MPSAFE in the syscall table. Is this still necessary? > > > > > > > > > I've been suspicious of this too, and I was hoping that you would have > > > > > an answer. Can we go ahead and correct this? > > > > > > > > I think we may need to check the calling of pipeclose() in pipe(), > > > > but as this is only done in an error case, it is probably safe enough > > > > to just grab Giant for that. (The mac_* calls may need to be checked > > > > too). > > > > > > pipeclose() seems to have some concept of locking, though I don't know > > > what the implications are of it saying, 'gee, the mutex on this pipe was > > > never initialized, so I just won't worry about locking.' Towards the > > > end of pipeclose() Giant is acquired, though that action is likely no > > > longer needed either. > > > > Nix that last part, I was looking at a stale file. pipeclose() does not > > explicitely grab Gaint. > > > > Scott > > > > > > I've run several buildworlds while doing background pipe tests, all > without any problems with WITNESS and INVARIANTS enabled on a fast SMP > machine. I can't report any performance change since I'm only testing > correctness now, but it looks promising. I'd advise to go ahead and > throw the switch on this. > This only changes the creation of pipes. Thus, I wouldn't expect an observable difference. I believe that the actual use of pipes has been free of Giant for some time. (In truth, there is a small bit of pmap-level code that still acquires Giant.) Alan
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