Hi Grant, Grant Grundler <grundler@xxxxxxxxxx> wrote: > On Thu, Jun 10, 2010 at 7:57 AM, Catalin Marinas > <catalin.marinas@xxxxxxx> wrote: >> The data in the cmd_block buffers may reach the main memory after the >> writel() to the device ports. > > "ia-64 Linux Kernel" (mosberger and eranian) uses exactly this sequence > as an example for wmb() on page 303. > > I'm curious about the system that exposed this problem. I believe wmb() fixes > an issue not exposed on most machines. Can any general comments be > made about cache coherency, memory ordering (weak?), instruction ordering > (super scalar?), etc. ? > > The explanation above is a bit short (most people won't understand it). I already posted a second version of this patch, though it triggered a longer discussion on whether we should do this (cross-post between LKML, linux-ide and linux-arch): http://thread.gmane.org/gmane.linux.ide/46414 I know IA-64 and a several other architectures have weak memory ordering but some of them just add barriers in the I/O accessors (with some performance penalty). Since the (new) patch is already in mainline, please comment on the other thread for memory ordering etc. Thanks. -- Catalin -- To unsubscribe from this list: send the line "unsubscribe linux-ide" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
