> Um, OK, you've said write twice now ... I was assuming you meant read. > Even on an x86, writes are posted, so there's no way a spin lock could > serialise a write without an intervening read to flush the posting > (that's why only reads have a relaxed version on altix). Or is there > something else I'm missing? Writes are posted yes, but not reordered arbitrarily. If I have code like: spin_lock(&mmio_lock); writel(val1, reg1); writel(val2, reg2); spin_unlock(&mmio_lock); then I have a reasonable expectation that if two CPUs run this at the same time, their writes to reg1/reg2 won't be interleaved with each other (because the whole section is inside a spinlock). And Altix violates that expectation. - R. -- To unsubscribe from this list: send the line "unsubscribe linux-arch" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
