Paul Mundt wrote: > On Mon, Jul 06, 2009 at 02:07:06PM +0200, Michal Simek wrote: > >> Arnd Bergmann wrote: >> >>> On Monday 06 July 2009, Michal Simek wrote: >>> >>> >>>>> Does this happen on microblaze-mmu or microblaze-nommu, or both? >>>>> The mmap code for the two is very different. >>>>> >>>>> >>>>> >>>> For MMU code. >>>> >>>> >>> Could this be a cache-aliasing problem? If your cache is 'virtually-indexed' >>> (most architectures are 'physically-indexed'), the kernel may have written >>> into different parts of the D-cache than what the user space is reading >>> from. If you have a write-through cache, that can explain why you only >>> see the stale data at the beginning of the page -- the cache controller >>> is still busy writing back the data when you start reading it from >>> DRAM through the cache alias. >>> >>> >> I don't think so because we run that test on Microblaze without caches >> and test failed too. >> I think that this is sufficient test to tell that the problem is not >> relate with caches. >> >> > Not necessarily, even on platforms that manage aliases in hardware > mappings that violate the aliasing constraints can still result in > undefined behaviour, this really depends more on your cache controller > and MMU than anything else. I notice that microblaze sets SHMLBA to > PAGE_SIZE, you may want to see if this test still breaks after bumping it > up to something like PAGE_SIZE * 4. > Yes, test still break - behavior is the same. I don't have accurate information about MMU unit but I will ask a question about. We are able to turn off cache controller directly in HW. > This is unfortunately one of the areas where what POSIX says is possible > and what hardware can support are at odds (you can look through > arch/sh/mm/mmap.c for a better idea). >
Thanks, Michal -- Michal Simek, Ing. (M.Eng) PetaLogix - Linux Solutions for a Reconfigurable World w: www.petalogix.com p: +61-7-30090663,+42-0-721842854 f: +61-7-30090663 ------------------------------------------------------------------------------ _______________________________________________ Ltp-list mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/ltp-list
