On Tue, Apr 16, 2013 at 01:43:09AM +0100, Colin Cross wrote: > On Mon, Apr 15, 2013 at 4:59 PM, Rob Herring <robherri...@gmail.com> wrote: > > Exclusive accesses still have further restrictions. From section 3.4.5: > > > > • It is IMPLEMENTATION DEFINED whether LDREX and STREX operations can be > > performed to a memory region > > with the Device or Strongly-ordered memory attribute. Unless the > > implementation documentation explicitly > > states that LDREX and STREX operations to a memory region with the > > Device or Strongly-ordered attribute are > > permitted, the effect of such operations is UNPREDICTABLE. > > > > > > Given that it is implementation defined, I don't see how Linux can rely > > on that behavior. > > I see, the problem is that while noncached and writecombined appear to > be similar mappings, noncached is mapped in PRRR to strongly-ordered, > while writecombined is mapped to unbufferable normal memory. > > I think adding a wmb() to persistent_ram_write is going to be > expensive on cpus with outer caches like the L2X0, where wmb() will > result in a spinlock. Is there a real SoC where this doesn't work?
A real SoC where exclusives don't work to memory not mapped as normal? Take your pick... Will -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
