Confirmed. This does not happen with vmalloc. The pointers are in quite different places in case that's relevant: kptr = ed460000 vptr = f23d1000 Aside: the reason I'm using kmalloc (or __get_free_pages()) is to have a physically contiguous buffer for DMA. I currently copy the framebuffer into a DMA buffer which is less efficient but works (thank goodness!). I will trace the bug myself when I get time. Conor. On Sat, Mar 15, 2014 at 11:29 AM, Conor O <falling174fps@xxxxxxxxx> wrote: > Hello all, I hope this is a reasonable place to post a bug. If I fix > it I can post a fix too. > > I believe there might be a bug in deferred io. In my fb driver I have > a block of memory, allocated with kmalloc, that I can mmap, write to, > and munmap perfectly fine using my own mmap routine. As soon as I > switch to deferred io, there's a problem: > > From userspace, I can mmap the framebuffer memory fine and write to > it. The deferred io driver routine is called and updates the display > perfectly correctly. As soon as I call munmap() I get a repeated > kernel messages. This happens on ARM but not under an Ubuntu > Virtualbox VM (x86): > > BUG: Bad page state in process fbtest1 pfn:ad11d > page:c0dc03a0 count:0 mapcount:0 mapping:edbf7144 index:0x1d > page flags: 0x94(referenced|dirty|slab) > Modules linked in: hhlcd28a(O) sysimgblt sysfillrect syscopyarea > fb_sys_fops bnep ipv6 mwifiex_sdio mwifiex btmrvl_sdio firmware_class > btmrvl cfg80211 bluetooth rfkill > [<c0014bc8>] (unwind_backtrace+0x0/0x11c) from [<c00c44d4>] (bad_page+0xd0/0xfc) > [<c00c44d4>] (bad_page+0xd0/0xfc) from [<c00c45c0>] > (free_pages_prepare+0xc0/0x150) > [<c00c45c0>] (free_pages_prepare+0xc0/0x150) from [<c00c5a34>] > (free_hot_cold_page+0x20/0x188) > [<c00c5a34>] (free_hot_cold_page+0x20/0x188) from [<c00c5dc4>] > (free_hot_cold_page_list+0x7c/0x9c) > [<c00c5dc4>] (free_hot_cold_page_list+0x7c/0x9c) from [<c00c90c0>] > (release_pages+0x1b4/0x1c8) > [<c00c90c0>] (release_pages+0x1b4/0x1c8) from [<c00ea854>] > (free_pages_and_swap_cache+0x8c/0x9c) > [<c00ea854>] (free_pages_and_swap_cache+0x8c/0x9c) from [<c00dfff4>] > (unmap_region+0x100/0x154) > [<c00dfff4>] (unmap_region+0x100/0x154) from [<c00e116c>] > (do_munmap+0x218/0x2a4) > [<c00e116c>] (do_munmap+0x218/0x2a4) from [<c00e1234>] (vm_munmap+0x3c/0x50) > [<c00e1234>] (vm_munmap+0x3c/0x50) from [<c000dc20>] (ret_fast_syscall+0x0/0x30) > > [repeated for N pages] > > root@duovero:~/testdrv# > > I will now convert to using vmalloc and check to see if this happens too. > > Thanks, > > Conor. -- To unsubscribe from this list: send the line "unsubscribe linux-fbdev" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
