Messages in this thread | | | Date | Wed, 10 May 2006 12:40:03 -0700 (PDT) | Subject | Re: [RFC/PATCH] Make powerpc64 use __thread for per-cpu variables | From | "David S. Miller" <> |
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From: Richard Henderson <rth@twiddle.net> Date: Wed, 10 May 2006 08:47:13 -0700
> How do you plan to address the compiler optimizing ... > Across the schedule, we may have changed cpus, making the cached > address invalid.
Per-cpu variables need to be accessed only with preemption disabled. And the preemption enable/disable operations provide a compiler memory barrier.
#define preempt_disable() \ do { \ inc_preempt_count(); \ barrier(); \ } while (0)
...
#define preempt_enable() \ do { \ preempt_enable_no_resched(); \ barrier(); \ preempt_check_resched(); \ } while (0)
The scheduler itself need to take care to not cause the situation you mention either.
Therefore this is an issue we had already, not some new thing introduced by using __thread for per-cpu variables. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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