I have counted a problem when i mmap the /dev/fb0 and memset it to 0( the fb driver use deferred_io and when i do not use deferred_io it works well) .This bug also showed int linux2.6.26 and linux2.6.25. does this bug solved? function fb_deferred_io_fault called<3>function fb_deferred_io_mkwrite called<3>function fb_deferred_io_fault called<3>function fb_deferred_io_mkwrite called<3>function fb_deferred_io_fault called<3>function fb_deferred_io_mkwrite called<2>kernel BUG at lib/radix-tree.c:474! Unable to handle kernel NULL pointer dereference at virtual address 00000000 pgd = c3ef8000 [00000000] *pgd=0bd25031, *pte=00000000, *ppte=00000000 Internal error: Oops: 817 [#2] Modules linked in: etrackfb_new sony_prs_505 CPU: 0 Tainted: G D W (2.6.26-rc9-00056-g99b0915-dirty #1) PC is at __bug+0x20/0x2c LR is at log_wait+0x0/0x8 pc : [<c002118c>] lr : [<c024f1f8>] psr: 20000093 sp : c3ed7d9c ip : c3ed7ce0 fp : c3ed7da8 r10: 00000002 r9 : 00000000 r8 : 40137000 r7 : 00000000 r6 : c3811294 r5 : 00000000 r4 : 00000000 r3 : 00000000 r2 : c024f214 r1 : 0001233d r0 : 00000027 Flags: nzCv IRQs off FIQs on Mode SVC_32 ISA ARM Segment user Control: c000717f Table: 0bef8000 DAC: 00000015 Process framebuff.ko (pid: 215, stack limit = 0xc3ed6260) Stack: (0xc3ed7d9c to 0xc3ed8000) 7d80: c3ed7dd8 7da0: c3ed7dac c01069d4 c002117c c3ed7db8 00000000 c0310b40 c3811290 00000000 7dc0: 40137000 c3d2c900 00000000 c3ed7df4 c3ed7ddc c00a639c c010692c c0310b40 7de0: 00000001 c3d1339c c3ed7e04 c3ed7df8 c00a65f8 c00a6248 c3ed7e1c c3ed7e08 7e00: c00660d8 c00a6554 c0310b40 00000001 c3ed7e34 c3ed7e20 c0066ba4 c006609c 7e20: 0bd5a0ff c0310b40 c3ed7e7c c3ed7e38 c006d684 c0066b9c c3ef9000 00000001 7e40: 00000001 00000001 00000002 40137000 c0310b40 c3ef8000 00000000 c3d20f00 7e60: c3d1339c 40137000 00000800 00001000 c3ed7ecc c3ed7e80 c006eb64 c006d318 7e80: 00000002 00000001 00000000 c02ffe60 c3d2c900 c3ed7eb4 000004dc c3ef9000 7ea0: c004c368 ffffffff c3d1339c c3d20f00 c3d2c938 c3d2c900 c3ed7fb0 40137000 7ec0: c3ed7f04 c3ed7ed0 c0022dc0 c006e8b8 c02ffe60 c3ef8000 00000817 ffffffff 7ee0: c024e630 00000817 c3ed7fb0 40137000 00000000 4012f000 c3ed7fac c3ed7f08 7f00: c001d1dc c0022ce8 00000000 000000fb c3d2c900 c3d30680 00000224 c3ef9000 7f20: 00076000 ffffffff 00000200 c3d136e4 c3ed7f4c c3ed7f40 c004f998 c0107a20 7f40: c3ed7f84 c3ed7f50 c0022e50 c004f998 00075300 c3ed7f70 00000000 ffffffff 7f60: 00001000 000086c0 00000001 00008520 00000000 4012f000 c3ed7f9c c3ed7f88 7f80: c0022f98 c0022ce8 ffffffff ffffffff 000086b4 000086c0 00000001 00008520 7fa0: 00000000 c3ed7fb0 c001d9c0 c001d1b0 40135000 00000000 000732f8 40137000 7fc0: beb2bed4 000086b4 000086c0 00000001 00008520 00000000 4012f000 beb2bea8 7fe0: 40089810 beb2bd6c 00008674 40089838 20000010 ffffffff ffffffff ffffffff Backtrace: [<c002116c>] (__bug+0x0/0x2c) from [<c01069d4>] (radix_tree_tag_set+0xb8/0xfc) [<c010691c>] (radix_tree_tag_set+0x0/0xfc) from [<c00a639c>] (__set_page_dirty+0x164/0x198) [<c00a6238>] (__set_page_dirty+0x0/0x198) from [<c00a65f8>] (__set_page_dirty_buffers+0xb4/0xc4) r6:c3d1339c r5:00000001 r4:c0310b40 [<c00a6544>] (__set_page_dirty_buffers+0x0/0xc4) from [<c00660d8>] (set_page_dirty+0x4c/0xd0) [<c006608c>] (set_page_dirty+0x0/0xd0) from [<c0066ba4>] (set_page_dirty_balance+0x18/0x5c) r5:00000001 r4:c0310b40 [<c0066b8c>] (set_page_dirty_balance+0x0/0x5c) from [<c006d684>] (__do_fault+0x37c/0x3a4) r5:c0310b40 r4:0bd5a0ff [<c006d308>] (__do_fault+0x0/0x3a4) from [<c006eb64>] (handle_mm_fault+0x2bc/0x5f0) [<c006e8a8>] (handle_mm_fault+0x0/0x5f0) from [<c0022dc0>] (do_page_fault+0xe8/0x224) [<c0022cd8>] (do_page_fault+0x0/0x224) from [<c001d1dc>] (do_DataAbort+0x3c/0xa0) [<c001d1a0>] (do_DataAbort+0x0/0xa0) from [<c001d9c0>] (ret_from_exception+0x0/0x10) Exception stack(0xc3ed7fb0 to 0xc3ed7ff8) 7fa0: 40135000 00000000 000732f8 40137000 7fc0: beb2bed4 000086b4 000086c0 00000001 00008520 00000000 4012f000 beb2bea8 7fe0: 40089810 beb2bd6c 00008674 40089838 20000010 ffffffff r8:00008520 r7:00000001 r6:000086c0 r5:000086b4 r4:ffffffff Code: e1a01000 e59f000c eb006243 e3a03000 (e5833000) ---[ end trace 4cc49dda9c86eac6 ]--- Segmentation fault