Messages in this thread |  | | | Date | Tue, 10 Mar 2009 06:25:08 -0400 | | Subject | Re: [PATCH 02/18] Blackfin Serial Driver: use barrier instead of cpu_relax for Blackfin SMP like patch | | From | Mike Frysinger <> |
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On Tue, Mar 10, 2009 at 06:07, gyang wrote: > On Fri, 2009-03-06 at 14:37 -0800, Andrew Morton wrote: >> On Fri, 6 Mar 2009 14:42:44 +0800 >> Bryan Wu <cooloney@kernel.org> wrote: >> >> > From: Graf Yang <graf.yang@analog.com> >> > >> > We are making a SMP like patch to blackfin, cpu_relax() is replaced by a >> > data cache flush function which will count it to a per-cpu counter. >> > If this serial function is called too early, the per-cpu data area have >> > not been initialized, this call will cause crash. >> >> That's a bug in blackfin architecture support. The kernel should be >> able to call cpu_relax() at any time, surely. It's a very low-level >> and simple thing. >> >> > So we'd like to use barrier() instead of cpu_relax(). >> > >> >> barrier() is purely a compiler concept. We might as well just remove >> the cpu_relax() altogether. > > Do you mean remove cpu_relax(), and either not add barrier() here?
afaik, early printk all runs before SMP is setup, so having it be a 100% busy wait is fine -mike -- 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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