* Suresh Siddha <suresh.b.siddha@xxxxxxxxx> wrote: > On Wed, 2009-02-18 at 05:59 -0800, Nick Piggin wrote: > > You're saying the problem is in generic_exec_single because I've > > removed the smp_mb that inadvertently also serialises memory with > > the x2apic on x86? > > yes. > > > > > Indeed that could cause problems on some architectures which I > > had hoped to avoid. So the patch is probably better off to first > > add the smp_mb() to arch_send_call_function_xxx arch code, unless > > it is immediately obvious or confirmed by arch maintainer that > > such barrier is not required. > > For x2apic specific operations we should add the smp_mb() sequence. But > we need to make sure that we don't end up doing it twice (once in > generic code and another in arch code) for all the ipi paths. right now we do have an smp_mb() due to your fix in November. So what should happen is to move that smp_mb() from the x86 generic IPI path to the x86 x2apic IPI path. (and turn it into an smp_wmb() - that should be enough - we dont care about future reads being done sooner than this point.) Ingo -- 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
