Re: [PATCH] tick/sched: fix data races at tick_do_timer_cpu

[Qian Cai]

> On Mar 4, 2020, at 4:56 AM, Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:
> 
> Worse:
> 
> +    if (cpu != READ_ONCE(tick_do_timer_cpu) &&
> +        (READ_ONCE(tick_do_timer_cpu) != TICK_DO_TIMER_NONE ||
> 
> Doing that read twice is just utterly stupid. And the patch is full of
> that :/
> 
> Please stop this non-thinking 'fix' generation!

That is an oversight that could easily be fixed. However, blaming about ânon-thinkingâ is rather harsh. Do you know I had spent weeks reading about memory-model.txt and alike just to get better at it?