Messages in this thread | | | Date | Tue, 10 Sep 2013 17:25:49 +0200 | From | Peter Zijlstra <> | Subject | Re: [PATCH 6/7] sched, x86: Provide a per-cpu preempt_count implementation |
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On Tue, Sep 10, 2013 at 07:02:51AM -0700, Eric Dumazet wrote: > 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 ?
Last time I tried using the proper this_cpu* stuff that all exploded in my face due to header recursion hell, so I've limited myself to what's available in arch/x86/include/asm/percpu.h.
It was a few weeks ago though and maybe I just didn't try hard enough.
> > +#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;
OK, that does indeed generate slightly better code.
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