On Fri, Jan 01, 2010 at 02:10:53PM +0000, David Laight wrote: > 1) the 'disk busy' count, this isn't a statistic so needs locking. > 2) cumulative counts of transfers and bytes, these are just stats so > don't necessarily need locking. The most likely 'error' is that one > of the addittions is lost, this is really below the noise floor. > A slight worry might be an error when a multi-word value wraps (eg > a 64bit counter on a 32bit machine that has no double-word memory > accesses). This is probably statistically unlikely enough to be > ignored as well.
It may not be documented but it's the driver's responsibility to provide locking for these. Have a look at ccd for an MP-safe example.
