cvs commit: src/sys/dev/io iodev.c

Alan Cox alc at
Fri Aug 8 17:08:17 UTC 2008

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.


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