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Date: Wed, 2 May 2007 20:05:43 +0200 From: Segher Boessenkool <segher@...nel.crashing.org> To: Scott Wood <scottwood@...escale.com> Cc: netdev@...r.kernel.org, linuxppc-dev@...abs.org, jgarzik@...ox.com Subject: Re: [PATCH] gianfar: Add I/O barriers when touching buffer descriptor ownership. >> AFAICS you need stronger barriers though; {w,r,}mb(), >> to prevent _any_ reordering of those memory accesses, >> not just the compiler-generated ones. > > My impression was that the eieio used by iobarrier would be sufficient > for that, as we're not trying to synchronize between accesses to > different types of memory. Is sync really required here? For accesses to main system memory, eieio only orders writes, not reads, so iobarrier_r() doesn't do what you want; and iobarrier_w() isn't meant to be used for main memory access ordering either. Also, it is better to not use powerpc-specific interfaces in a device driver if you don't have a strong reason to. Segher - To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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