Date: Fri, 08 Aug 2008 12:08:15 -0500 From: Alan Cox <alc@cs.rice.edu> To: John Baldwin <jhb@freebsd.org> Cc: cvs-src@freebsd.org, src-committers@freebsd.org, Ed Schouten <ed@freebsd.org>, cvs-all@freebsd.org Subject: Re: cvs commit: src/sys/dev/io iodev.c Message-ID: <489C7D7F.4090806@cs.rice.edu> In-Reply-To: <200808081226.32089.jhb@freebsd.org> References: <200808081343.m78DhwYE068477@repoman.freebsd.org> <200808081226.32089.jhb@freebsd.org>
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John Baldwin wrote: > >Also, I don't see why memrw() is not MPSAFE actually (on amd64 and i386 at >least). Stephan (ups@) even has a comment to that effect. The MTRR stuff >backing memioctl() on x86 might need locking, but I think that is all mem(4) >is missing. > > > There is nothing there that requires Giant specifically. However, the use of some lock in memrw() does have an arguably useful but small effect: overlapping operations will be serialized. So, if you're ever trying to debug something involving memrw(), you won't be staring at essentially random state. Alan
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