Christoph Lameter said, at 2012/11/1 1:35:
> It would be better to use
>
> this_cpu_read(tfms)
>
> since that would also make it atomic vs interrupts. The above code (both
> original and modified) could determine a pointer to a per cpu structure
> and then take an interrupt which would move the task. On return we would
> be accessing the per cpu variable of another processor.
this_cpu_read
|-----_this_cpu_generic_read
#define _this_cpu_generic_read(pcp) \
({ typeof(pcp) ret__; \
preempt_disable(); \
ret__ = *this_cpu_ptr(&(pcp)); \
preempt_enable(); \
ret__; \
})
this_cpu_read operations locate per-cpu variable with preemption safeļ¼ not
disable interrupts. why is it atomic vs interrupts?
I have no idea whether we need to disable preemption for this code?
At least, xfrm code run well with per_cpu_ptr which don't disable preemption.
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