Re: [patch 10/19] preempt: Cleanup the macro maze a bit

Peter Zijlstra
2020-11-16T12:38:28Z

On Fri, Nov 13, 2020 at 03:02:17PM +0100, Thomas Gleixner wrote:

> -#define irq_count() (preempt_count() & (HARDIRQ_MASK | SOFTIRQ_MASK \
> - | NMI_MASK))
> +#define irq_count() (nmi_count() | hardirq_count() | softirq_count())

> +#define in_task() (!(in_nmi() | in_hardirq() | in_serving_softirq()))
> -#define in_task() (!(preempt_count() & \
> - (NMI_MASK | HARDIRQ_MASK | SOFTIRQ_OFFSET)))

How horrible is the code-gen? Because preempt_count() is
raw_cpu_read_4() and at least some old compilers will refuse to CSE it
(consider the this_cpu_read_stable mess).