Russell, Hi, Kukjin Kim wrote: > Russell wrote: > > So, memory starts at 0x20000000 and finishes at 0x25000000. That's fine. > > That doesn't mean the section size is 16MB. > > > > As I've already said, the section size has _nothing_ what so ever to do > > with the size of memory, or the granularity of the size of memory. By > > way of illustration, it is perfectly legal to have a section size of > > 256MB but only have 1MB in a section and this is perfectly legal. So > > sections do not have to be completely filled. > > > Actually, as you know, the hole's area of mem_map is freed from bootmem if a > section has a hole when initializing sparse memory. > > I identified that a section doesn't need to be a contiguous area of physical > memory when reading your comment with the fact that the mem_map of a section > can be smaller than the size of a section. > > I found, however, the kernel panics when modifying min_free_kbytes file in > the proc filesystem if a section has a hole. > > While processing the change of min_free_kbytes in the kernel, page > descriptors in a hole of an online section is accessed. As I said, following error happens. It would be helpful to me if any opinions or comments. --- When SECTION_SIZE_BITS is 24 (16MiB), [root@Samsung ~]# cat /proc/sys/vm/min_free_kbytes 2736 [root@Samsung ~]# echo "2730" > /proc/sys/vm/min_free_kbytes [root@Samsung ~]# cat /proc/sys/vm/min_free_kbytes 2730 [root@Samsung ~]# When SECTION_SIZE_BITS is 28 (256MiB), [root@Samsung ~]# cat /proc/sys/vm/min_free_kbytes 2736 [root@Samsung ~]# echo "2730" > /proc/sys/vm/min_free_kbytes Unable to handle kernel NULL pointer dereference at virtual address 00000004 pgd = 80a14000 [00000004] *pgd=20a0b031, *pte=00000000, *ppte=00000000 Internal error: Oops: 17 [#1] PREEMPT last sysfs file: Modules linked in: CPU: 0 Not tainted (2.6.35-rc4-00007-g9a59bf7-dirty #3) PC is at get_pageblock_flags_group+0x54/0xa8 LR is at setup_per_zone_wmarks+0xfc/0x1d4 pc : [<800686cc>] lr : [<800691a0>] psr: 60000093 sp : 80a03ed0 ip : 00000001 fp : 00058000 r10: 004a0000 r9 : 801e5fbc r8 : 802c0000 r7 : 0001c900 r6 : 00025000 r5 : 801e5fa4 r4 : 0000007e r3 : 00000018 r2 : 00000002 r1 : 00000000 r0 : 00000000 Flags: nZCv IRQs off FIQs on Mode SVC_32 ISA ARM Segment user Control: 10c5387d Table: 20a14019 DAC: 00000015 Process bash (pid: 888, stack limit = 0x80a022e8) Stack: (0x80a03ed0 to 0x80a04000) 3ec0: 00000000 801e5fa4 00025000 800691a0 3ee0: a0000013 000002aa 00000005 00000001 801d8254 2aacb000 00000005 00000001 3f00: 80a02000 80a03f80 00000001 80069354 80a03f80 00000001 801d7900 800d2734 3f20: 80a03f80 00000000 00000000 00000005 80a0903c 00000005 b7c81c00 2aacb000 3f40: 80a03f80 00000005 00000000 800d2760 00000001 2aacb000 00000005 8008ff74 3f60: b7c81c00 2aacb000 b7c81c00 2aacb000 00000000 00000000 00000005 800900c8 3f80: 00000005 00000000 00000005 00000000 00000005 2aacb000 2ac525f8 00000004 3fa0: 8001f0e8 8001ef40 00000005 2aacb000 00000001 2aacb000 00000005 00000000 3fc0: 00000005 2aacb000 2ac525f8 00000004 00000005 000babe0 00000000 00000001 3fe0: 2aacb000 7e88ca58 2ab99124 2abe643c 60000010 00000001 00000000 00000000 [<800686cc>] (get_pageblock_flags_group+0x54/0xa8) from [<800691a0>] (setup_per_zone_wmarks+0xfc/0x1d4) [<800691a0>] (setup_per_zone_wmarks+0xfc/0x1d4) from [<80069354>] (min_free_kbytes_sysctl_handler+0x20/0x28) [<80069354>] (min_free_kbytes_sysctl_handler+0x20/0x28) from [<800d2734>] (proc_sys_call_handler+0x90/0xac) [<800d2734>] (proc_sys_call_handler+0x90/0xac) from [<800d2760>] (proc_sys_write+0x10/0x14) [<800d2760>] (proc_sys_write+0x10/0x14) from [<8008ff74>] (vfs_write+0xac/0x154) [<8008ff74>] (vfs_write+0xac/0x154) from [<800900c8>] (sys_write+0x3c/0x68) [<800900c8>] (sys_write+0x3c/0x68) from [<8001ef40>] (ret_fast_syscall+0x0/0x30) Code: 11a0cb8c 11a0cbac 1080018c e3a0c001 (e5904004) ---[ end trace 8b96cc6afed783d1 ]--- note: bash[888] exited with preempt_count 1 BUG: scheduling while atomic: bash/888/0x40000002 Modules linked in: [<80024558>] (unwind_backtrace+0x0/0xec) from [<8014f110>] (schedule+0x6c/0x2e4) [<8014f110>] (schedule+0x6c/0x2e4) from [<80035f74>] (__cond_resched+0x24/0x34) [<80035f74>] (__cond_resched+0x24/0x34) from [<8014f484>] (_cond_resched+0x30/0x40) [<8014f484>] (_cond_resched+0x30/0x40) from [<8007ac1c>] (unmap_vmas+0x550/0x604) [<8007ac1c>] (unmap_vmas+0x550/0x604) from [<8007d6b8>] (exit_mmap+0xb0/0x1d8) [<8007d6b8>] (exit_mmap+0xb0/0x1d8) from [<80037de8>] (mmput+0x4c/0x104) [<80037de8>] (mmput+0x4c/0x104) from [<8003b7f4>] (exit_mm+0x104/0x10c) [<8003b7f4>] (exit_mm+0x104/0x10c) from [<8003cdc4>] (do_exit+0x194/0x5bc) [<8003cdc4>] (do_exit+0x194/0x5bc) from [<80022950>] (die+0x190/0x1bc) [<80022950>] (die+0x190/0x1bc) from [<80025488>] (__do_kernel_fault+0x64/0x84) [<80025488>] (__do_kernel_fault+0x64/0x84) from [<8002567c>] (do_page_fault+0x1d4/0x1ec) [<8002567c>] (do_page_fault+0x1d4/0x1ec) from [<8001e2d0>] (do_DataAbort+0x34/0x94) [<8001e2d0>] (do_DataAbort+0x34/0x94) from [<8001ea2c>] (__dabt_svc+0x4c/0x60) Exception stack(0x80a03e88 to 0x80a03ed0) 3e80: 00000000 00000000 00000002 00000018 0000007e 801e5fa4 3ea0: 00025000 0001c900 802c0000 801e5fbc 004a0000 00058000 00000001 80a03ed0 3ec0: 800691a0 800686cc 60000093 ffffffff [<8001ea2c>] (__dabt_svc+0x4c/0x60) from [<800686cc>] (get_pageblock_flags_group+0x54/0xa8) [<800686cc>] (get_pageblock_flags_group+0x54/0xa8) from [<800691a0>] (setup_per_zone_wmarks+0xfc/0x1d4) [<800691a0>] (setup_per_zone_wmarks+0xfc/0x1d4) from [<80069354>] (min_free_kbytes_sysctl_handler+0x20/0x28) [<80069354>] (min_free_kbytes_sysctl_handler+0x20/0x28) from [<800d2734>] (proc_sys_call_handler+0x90/0xac) [<800d2734>] (proc_sys_call_handler+0x90/0xac) from [<800d2760>] (proc_sys_write+0x10/0x14) [<800d2760>] (proc_sys_write+0x10/0x14) from [<8008ff74>] (vfs_write+0xac/0x154) [<8008ff74>] (vfs_write+0xac/0x154) from [<800900c8>] (sys_write+0x3c/0x68) [<800900c8>] (sys_write+0x3c/0x68) from [<8001ef40>] (ret_fast_syscall+0x0/0x30) BUG: spinlock lockup on CPU#0, bash/888, 801e5fbc [<80024558>] (unwind_backtrace+0x0/0xec) from [<801098a8>] (do_raw_spin_lock+0x110/0x14c) [<801098a8>] (do_raw_spin_lock+0x110/0x14c) from [<8006963c>] (free_pcppages_bulk+0x24/0x2f4) [<8006963c>] (free_pcppages_bulk+0x24/0x2f4) from [<80069f28>] (free_hot_cold_page+0x15c/0x180) [<80069f28>] (free_hot_cold_page+0x15c/0x180) from [<8007b834>] (free_pgd_range+0x15c/0x17c) [<8007b834>] (free_pgd_range+0x15c/0x17c) from [<8007b8e4>] (free_pgtables+0x90/0x9c) [<8007b8e4>] (free_pgtables+0x90/0x9c) from [<8007d714>] (exit_mmap+0x10c/0x1d8) [<8007d714>] (exit_mmap+0x10c/0x1d8) from [<80037de8>] (mmput+0x4c/0x104) [<80037de8>] (mmput+0x4c/0x104) from [<8003b7f4>] (exit_mm+0x104/0x10c) [<8003b7f4>] (exit_mm+0x104/0x10c) from [<8003cdc4>] (do_exit+0x194/0x5bc) [<8003cdc4>] (do_exit+0x194/0x5bc) from [<80022950>] (die+0x190/0x1bc) [<80022950>] (die+0x190/0x1bc) from [<80025488>] (__do_kernel_fault+0x64/0x84) [<80025488>] (__do_kernel_fault+0x64/0x84) from [<8002567c>] (do_page_fault+0x1d4/0x1ec) [<8002567c>] (do_page_fault+0x1d4/0x1ec) from [<8001e2d0>] (do_DataAbort+0x34/0x94) [<8001e2d0>] (do_DataAbort+0x34/0x94) from [<8001ea2c>] (__dabt_svc+0x4c/0x60) Exception stack(0x80a03e88 to 0x80a03ed0) 3e80: 00000000 00000000 00000002 00000018 0000007e 801e5fa4 3ea0: 00025000 0001c900 802c0000 801e5fbc 004a0000 00058000 00000001 80a03ed0 3ec0: 800691a0 800686cc 60000093 ffffffff [<8001ea2c>] (__dabt_svc+0x4c/0x60) from [<800686cc>] (get_pageblock_flags_group+0x54/0xa8) [<800686cc>] (get_pageblock_flags_group+0x54/0xa8) from [<800691a0>] (setup_per_zone_wmarks+0xfc/0x1d4) [<800691a0>] (setup_per_zone_wmarks+0xfc/0x1d4) from [<80069354>] (min_free_kbytes_sysctl_handler+0x20/0x28) [<80069354>] (min_free_kbytes_sysctl_handler+0x20/0x28) from [<800d2734>] (proc_sys_call_handler+0x90/0xac) [<800d2734>] (proc_sys_call_handler+0x90/0xac) from [<800d2760>] (proc_sys_write+0x10/0x14) [<800d2760>] (proc_sys_write+0x10/0x14) from [<8008ff74>] (vfs_write+0xac/0x154) [<8008ff74>] (vfs_write+0xac/0x154) from [<800900c8>] (sys_write+0x3c/0x68) [<800900c8>] (sys_write+0x3c/0x68) from [<8001ef40>] (ret_fast_syscall+0x0/0x30) Thanks. Best regards, Kgene. -- Kukjin Kim <kgene.kim@xxxxxxxxxxx>, Senior Engineer, SW Solution Development Team, Samsung Electronics Co., Ltd. -- To unsubscribe from this list: send the line "unsubscribe linux-samsung-soc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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