Re: [PATCH 6/7] sched, x86: Provide a per-cpu preempt_countimplementation
From: Eric Dumazet
Date: Tue Sep 10 2013 - 10:02:59 EST
On Tue, 2013-09-10 at 15:08 +0200, Peter Zijlstra wrote:
> +static __always_inline int preempt_count(void)
> +{
> + return __this_cpu_read_4(__preempt_count) & ~PREEMPT_NEED_RESCHED;
> +}
Not sure why you used the _4 prefix on all accessors ?
>
> +#ifdef CONFIG_PREEMPT_COUNT
> + /*
> + * If it were not for PREEMPT_ACTIVE we could guarantee that the
> + * preempt_count of all tasks was equal here and this would not be
> + * needed.
> + */
> + task_thread_info(prev_p)->saved_preempt_count = __raw_get_cpu_var(__preempt_count);
this_cpu_read(__preempt_count) ?
> + __raw_get_cpu_var(__preempt_count) = task_thread_info(next_p)->saved_preempt_count;
this_cpu_write(__preempt_count,
task_thread_info(next_p)->saved_preempt_count;
> +#endif
> +
> this_cpu_write(kernel_stack,
> (unsigned long)task_stack_page(next_p) +
> THREAD_SIZE - KERNEL_STACK_OFFSET);
>
>
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