Messages in this thread | | | From | Kevin Hilman <> | Subject | Re: [GIT PULL] cputime: Full dynticks task/cputime accounting v7 | Date | Wed, 20 Feb 2013 10:48:53 -0800 |
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Frederic Weisbecker <fweisbec@gmail.com> writes:
> 2013/2/15 Kevin Hilman <khilman@linaro.org>: >> Frederic Weisbecker <fweisbec@gmail.com> writes: >> >>> Ingo, >>> >>> Please pull the new full dynticks cputime accounting code that >>> can be found at: >>> >>> git://git.kernel.org/pub/scm/linux/kernel/git/frederic/linux-dynticks.git >>> tags/full-dynticks-cputime-for-mingo >>> >>> My last concern is the dependency on CONFIG_64BIT. We rely on cputime_t >>> being u64 for reasonable nanosec granularity implementation. And therefore >>> we need a single instruction fetch to read kernel cpustat for atomicity >>> requirement against concurrent incrementation, which only 64 bit archs >>> can provide. >> >> Actually, moderately recent 32-bit ARMs can do atomic 64-bit load/stores >> too. > > Does gcc automatically handle 64 bit store/loads in one way or does > that require specific CPU instructions?
For atomic load/stores, it requires specific instructions that gcc will not generate, so the atomic64 accessors are needed on ARM.
Kevin
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