On Thu, 2013-02-21 at 21:56 -0800, Kevin Hilman wrote:
On 64-bit platforms, reads/writes of the various cpustat fields are atomic due to native 64-bit loads/stores. However, on non 64-bit platforms, reads/writes of the cpustat fields are not atomic and could lead to inconsistent statistics.
Which is a problem how?
This problem was originally reported by Frederic Weisbecker as a 64-bit limitation with the nsec granularity cputime accounting for full dynticks, but then we realized that it's a problem that's been around for awhile and not specific to the new cputime accounting.
This series fixes this by first converting all access to the cputime fields to use accessor functions, and then converting the accessor functions to use the atomic64 functions.
Argh!! at what cost? 64bit atomics are like expensive. Wouldn't adding a seqlock be saner?