Hi greg, I write a module for inserting a PCB or delete a PCB to kernel's PCB tree, but when i run it something wrong happens to me like following. My environment is "Linux 10 2.6.35-22-generic #33-Ubuntu SMP Sun Sep 19 20:34:50 UTC 2010 i686 GNU/Linux" hw2.c #include <linux/module.h> #include <linux/kernel.h> #include <linux/init.h> #include <linux/sched.h> #include <linux/list.h> #include <linux/slab.h> struct pcb { int pid; int state; int flag; char *comm; struct list_head tasks; }; static int insert_task(struct task_struct *p) { struct pcb *pcb1 = NULL; pcb1 = (struct pcb *)kmalloc(sizeof(struct pcb), GFP_KERNEL); if (NULL == pcb1) { printk("<0> kmalloc failed!\n"); } pcb1->state = 8; pcb1->flag = 8; pcb1->pid= 2; pcb1->comm = "jiawei"; list_add(&pcb1->tasks, &p->tasks); return 0; } static int rm_task(struct task_struct *p){ struct task_struct *del = p; list_del(&p->tasks); // kfree(del); return 0; } #if 1 static int print_pid(void) { struct task_struct *task = NULL; struct task_struct *p = NULL; struct list_head *pos = NULL; int count = 0; printk("Search for insert task-------->\n"); task = &init_task; list_for_each(pos, &task->tasks) { p = list_entry(pos, struct task_struct, tasks); count++; if (0 == p->pid) { rm_task(p); } printk("pid: %d, state: %ld, comm: %s\n", p->pid, p->state, p->comm); } insert_task(p); printk("the number of process is %d\n", count); count = 0; printk("show all tasks-------->\n"); task = &init_task; list_for_each(pos, &task->tasks) { p = list_entry(pos, struct task_struct, tasks); count++; printk("pid: %d, state: %ld, comm: %s\n", p->pid, p->state, p->comm); } printk("the number of process is %d\n", count); return 0; } #endif static int __init hello_init(void) { printk("<1> Hello World\n"); print_pid(); return 0; } static void __exit hello_exit(void) { printk("<1> Goodbey\n"); return ; } MODULE_LICENSE("GPL"); module_init(hello_init); module_exit(hello_exit); Dmesg logs: [ 1174.738305] Search for insert task--------> [ 1174.738308] pid: 1, state: 1, comm: init [ 1174.738312] pid: 2, state: 1, comm: kthreadd [ 1174.738316] pid: 3, state: 1, comm: ksoftirqd/0 [ 1174.738319] pid: 4, state: 1, comm: migration/0 [ 1174.738323] pid: 5, state: 1, comm: watchdog/0 [ 1174.738326] pid: 6, state: 1, comm: events/0 [ 1174.738329] pid: 7, state: 1, comm: cpuset [ 1174.738333] pid: 8, state: 1, comm: khelper [ 1174.738336] pid: 9, state: 1, comm: netns [ 1174.738340] pid: 10, state: 1, comm: async/mgr [ 1174.738343] pid: 11, state: 1, comm: pm [ 1174.738346] pid: 12, state: 1, comm: sync_supers [ 1174.738350] pid: 13, state: 1, comm: bdi-default [ 1174.738353] pid: 14, state: 1, comm: kintegrityd/0 [ 1174.738357] pid: 15, state: 1, comm: kblockd/0 [ 1174.738360] pid: 16, state: 1, comm: ata_aux [ 1174.738364] pid: 17, state: 1, comm: ata_sff/0 [ 1174.738367] pid: 18, state: 1, comm: khubd [ 1174.738370] pid: 19, state: 1, comm: kseriod [ 1174.738374] pid: 20, state: 1, comm: kmmcd [ 1174.738377] pid: 23, state: 1, comm: kswapd0 [ 1174.738380] pid: 24, state: 1, comm: ksmd [ 1174.738383] pid: 25, state: 1, comm: aio/0 [ 1174.738387] pid: 26, state: 1, comm: ecryptfs-kthrea [ 1174.738390] pid: 27, state: 1, comm: crypto/0 [ 1174.738394] pid: 33, state: 1, comm: scsi_eh_0 [ 1174.738397] pid: 35, state: 1, comm: scsi_eh_1 [ 1174.738400] pid: 38, state: 1, comm: kstriped [ 1174.738404] pid: 39, state: 1, comm: kmpathd/0 [ 1174.738407] pid: 40, state: 1, comm: kmpath_handlerd [ 1174.738411] pid: 41, state: 1, comm: ksnapd [ 1174.738414] pid: 42, state: 1, comm: kondemand/0 [ 1174.738417] pid: 43, state: 1, comm: kconservative/0 [ 1174.738421] pid: 147, state: 1, comm: scsi_eh_2 [ 1174.738424] pid: 148, state: 1, comm: scsi_eh_3 [ 1174.738427] pid: 160, state: 1, comm: jbd2/sda1-8 [ 1174.738431] pid: 161, state: 1, comm: ext4-dio-unwrit [ 1174.738434] pid: 194, state: 1, comm: flush-8:0 [ 1174.738438] pid: 223, state: 1, comm: upstart-udev-br [ 1174.738441] pid: 225, state: 1, comm: udevd [ 1174.738445] pid: 284, state: 1, comm: udevd [ 1174.738448] pid: 289, state: 1, comm: udevd [ 1174.738451] pid: 323, state: 1, comm: kpsmoused [ 1174.738455] pid: 477, state: 1, comm: hd-audio0 [ 1174.738458] pid: 502, state: 1, comm: sshd [ 1174.738462] pid: 506, state: 1, comm: rsyslogd [ 1174.738465] pid: 529, state: 1, comm: dbus-daemon [ 1174.738469] pid: 561, state: 1, comm: gdm-binary [ 1174.738472] pid: 566, state: 1, comm: NetworkManager [ 1174.738476] pid: 577, state: 1, comm: avahi-daemon [ 1174.738479] pid: 586, state: 1, comm: avahi-daemon [ 1174.738483] pid: 587, state: 1, comm: modem-manager [ 1174.738486] pid: 597, state: 1, comm: console-kit-dae [ 1174.738490] pid: 675, state: 1, comm: gdm-simple-slav [ 1174.738493] pid: 679, state: 1, comm: cupsd [ 1174.738497] pid: 684, state: 1, comm: wpa_supplicant [ 1174.738501] pid: 688, state: 1, comm: dhclient [ 1174.738504] pid: 707, state: 1, comm: Xorg [ 1174.738507] pid: 742, state: 1, comm: getty [ 1174.738511] pid: 748, state: 1, comm: getty [ 1174.738514] pid: 758, state: 1, comm: getty [ 1174.738517] pid: 760, state: 1, comm: getty [ 1174.738520] pid: 764, state: 1, comm: getty [ 1174.738524] pid: 766, state: 1, comm: acpid [ 1174.738527] pid: 771, state: 1, comm: cron [ 1174.738530] pid: 772, state: 1, comm: atd [ 1174.738534] pid: 909, state: 1, comm: dbus-launch [ 1174.738537] pid: 978, state: 1, comm: gdm-session-wor [ 1174.738541] pid: 986, state: 1, comm: upowerd [ 1174.738544] pid: 990, state: 1, comm: rtkit-daemon [ 1174.738548] pid: 1000, state: 1, comm: polkitd [ 1174.738551] pid: 1071, state: 1, comm: getty [ 1174.738555] pid: 1082, state: 1, comm: gnome-keyring-d [ 1174.738559] pid: 1101, state: 1, comm: gnome-session [ 1174.738562] pid: 1128, state: 1, comm: ibus-daemon [ 1174.738566] pid: 1132, state: 1, comm: ssh-agent [ 1174.738569] pid: 1135, state: 1, comm: dbus-launch [ 1174.738573] pid: 1136, state: 1, comm: dbus-daemon [ 1174.738576] pid: 1142, state: 1, comm: gconfd-2 [ 1174.738580] pid: 1146, state: 1, comm: gnome-power-man [ 1174.738583] pid: 1152, state: 1, comm: gnome-settings- [ 1174.738587] pid: 1157, state: 1, comm: gvfsd [ 1174.738590] pid: 1162, state: 1, comm: gvfs-fuse-daemo [ 1174.738593] pid: 1170, state: 1, comm: polkit-gnome-au [ 1174.738597] pid: 1172, state: 1, comm: pulseaudio [ 1174.738600] pid: 1173, state: 1, comm: bluetooth-apple [ 1174.738604] pid: 1176, state: 1, comm: evolution-alarm [ 1174.738608] pid: 1177, state: 1, comm: nm-applet [ 1174.738611] pid: 1178, state: 1, comm: gnome-panel [ 1174.738615] pid: 1180, state: 1, comm: metacity [ 1174.738618] pid: 1182, state: 1, comm: nautilus [ 1174.738621] pid: 1189, state: 1, comm: gconf-helper [ 1174.738625] pid: 1202, state: 1, comm: ibus-gconf [ 1174.738629] pid: 1204, state: 1, comm: python [ 1174.738632] pid: 1206, state: 1, comm: ibus-x11 [ 1174.738635] pid: 1214, state: 1, comm: ibus-engine-pin [ 1174.738639] pid: 1226, state: 1, comm: gvfs-gdu-volume [ 1174.738642] pid: 1249, state: 1, comm: udisks-daemon [ 1174.738646] pid: 1271, state: 1, comm: udisks-daemon [ 1174.738649] pid: 1279, state: 1, comm: gvfs-afc-volume [ 1174.738653] pid: 1281, state: 1, comm: gvfsd-trash [ 1174.738656] pid: 1284, state: 1, comm: gvfs-gphoto2-vo [ 1174.738660] pid: 1289, state: 1, comm: gnome-screensav [ 1174.738663] pid: 1291, state: 1, comm: bonobo-activati [ 1174.738667] pid: 1299, state: 1, comm: wnck-applet [ 1174.738670] pid: 1301, state: 1, comm: trashapplet [ 1174.738674] pid: 1313, state: 1, comm: indicator-apple [ 1174.738677] pid: 1317, state: 1, comm: clock-applet [ 1174.738681] pid: 1318, state: 1, comm: indicator-apple [ 1174.738684] pid: 1319, state: 1, comm: notification-ar [ 1174.738688] pid: 1329, state: 1, comm: indicator-me-se [ 1174.738691] pid: 1333, state: 1, comm: indicator-sessi [ 1174.738695] pid: 1337, state: 1, comm: gvfsd-burn [ 1174.738698] pid: 1343, state: 1, comm: indicator-messa [ 1174.738702] pid: 1347, state: 1, comm: indicator-appli [ 1174.738705] pid: 1349, state: 1, comm: indicator-sound [ 1174.738709] pid: 1350, state: 1, comm: gdu-notificatio [ 1174.738712] pid: 1353, state: 1, comm: gnome-terminal [ 1174.738716] pid: 1356, state: 1, comm: gnome-pty-helpe [ 1174.738719] pid: 1357, state: 1, comm: bash [ 1174.738722] pid: 1381, state: 1, comm: firefox [ 1174.738726] pid: 1385, state: 1, comm: run-mozilla.sh [ 1174.738729] pid: 1389, state: 1, comm: firefox-bin [ 1174.738733] pid: 1419, state: 1, comm: applet.py [ 1174.738736] pid: 1427, state: 1, comm: sshd [ 1174.738740] pid: 1519, state: 1, comm: sshd [ 1174.738743] pid: 1520, state: 1, comm: bash [ 1174.738746] pid: 1557, state: 1, comm: update-notifier [ 1174.738750] pid: 1561, state: 1, comm: sshd [ 1174.738753] pid: 1657, state: 1, comm: sshd [ 1174.738756] pid: 1658, state: 1, comm: bash [ 1174.738760] pid: 1671, state: 1, comm: sshd [ 1174.738763] pid: 1784, state: 1, comm: sshd [ 1174.738766] pid: 1785, state: 1, comm: bash [ 1174.738769] pid: 1812, state: 1, comm: sshd [ 1174.738773] pid: 1911, state: 1, comm: sshd [ 1174.738776] pid: 1912, state: 1, comm: bash [ 1174.738779] pid: 1925, state: 1, comm: sshd [ 1174.738783] pid: 2038, state: 1, comm: sshd [ 1174.738786] pid: 2039, state: 1, comm: bash [ 1174.738789] pid: 2170, state: 1, comm: su [ 1174.738792] pid: 2177, state: 1, comm: bash [ 1174.738796] pid: 2285, state: 1, comm: vim [ 1174.738799] pid: 2319, state: 1, comm: vim [ 1174.738802] pid: 2320, state: 1, comm: sshd [ 1174.738806] pid: 2413, state: 1, comm: bash [ 1174.738809] pid: 2456, state: 1, comm: man [ 1174.738812] pid: 2465, state: 1, comm: pager [ 1174.738816] pid: 2474, state: 1, comm: su [ 1174.738819] pid: 2481, state: 1, comm: bash [ 1174.738822] pid: 0, state: 1, comm: [ 1174.738840] BUG: unable to handle kernel paging request at 00100100 [ 1174.738845] IP: [<f072a08d>] hello_init+0x8d/0x1c8 [hw2] [ 1174.738853] *pde = 00000000 [ 1174.738857] Oops: 0000 [#3] SMP [ 1174.738860] last sysfs file: /sys/devices/pci0000:00/0000:00:03.3/usb1/1-0:1.0/uevent [ 1174.738865] Modules linked in: hw2(+) hw1(+) binfmt_misc parport_pc ppdev snd_hda_codec_realtek snd_hda_intel snd_hda_codec snd_hwdep snd_pcm snd_seq_midi snd_rawmidi snd_seq_midi_event snd_seq snd_timer snd_seq_device snd sis_agp psmouse serio_raw soundcore snd_page_alloc shpchp agpgart lp parport 8139too 8139cp sata_sis mii [last unloaded: hw1] [ 1174.738895] [ 1174.738900] Pid: 4340, comm: insmod Tainted: G D 2.6.35-22-generic #33-Ubuntu / [ 1174.738904] EIP: 0060:[<f072a08d>] EFLAGS: 00010292 CPU: 0 [ 1174.738908] EIP is at hello_init+0x8d/0x1c8 [hw2] [ 1174.738911] EAX: 0000002b EBX: 00100100 ECX: c07cdd3c EDX: 00000000 [ 1174.738914] ESI: d85650e0 EDI: 00000097 EBP: d8781f5c ESP: d8781f34 [ 1174.738917] DS: 007b ES: 007b FS: 00d8 GS: 00e0 SS: 0068 [ 1174.738921] Process insmod (pid: 4340, ti=d8780000 task=ef098000 task.ti=d8780000) [ 1174.738923] Stack: [ 1174.738925] f07210d8 00000000 00000001 d85653d0 00000001 c07d0f50 00000001 096bb018 [ 1174.738933] <0> f0721120 00000000 d8781f88 c0101132 f0721120 c07d0f60 096bb018 f0721120 [ 1174.738940] <0> 00004000 f072a000 096bb018 f0721120 00004000 d8781fac c0180c2b 00000003 [ 1174.738948] Call Trace: [ 1174.738958] [<c0101132>] ? do_one_initcall+0x32/0x1a0 [ 1174.738963] [<f072a000>] ? hello_init+0x0/0x1c8 [hw2] [ 1174.738969] [<c0180c2b>] ? sys_init_module+0x9b/0x1e0 [ 1174.738975] [<c02169c5>] ? sys_close+0x75/0xc0 [ 1174.738982] [<c05c90a4>] ? syscall_call+0x7/0xb [ 1174.738984] Code: 00 00 00 02 20 00 8b 16 8d 8e f0 02 00 00 83 c7 01 89 4c 24 0c 89 44 24 04 c7 04 24 d8 10 72 f0 89 54 24 08 e8 b0 c3 e9 cf 8b 1b <8b> 03 0f 18 00 90 81 fb 90 78 7c c0 75 92 ba d0 00 00 00 b8 68 [ 1174.739024] EIP: [<f072a08d>] hello_init+0x8d/0x1c8 [hw2] SS:ESP 0068:d8781f34 [ 1174.739030] CR2: 0000000000100100 [ 1174.739035] ---[ end trace babb4642fde28352 ]--- [ 1620.965086] ------------[ cut here ]------------ [ 1620.965105] WARNING: at /build/buildd/linux-2.6.35/net/sched/sch_generic.c:258 dev_watchdog+0x1fd/0x210() [ 1620.965109] NETDEV WATCHDOG: eth1 (8139too): transmit queue 0 timed out [ 1620.965112] Modules linked in: hw2(+) hw1(+) binfmt_misc parport_pc ppdev snd_hda_codec_realtek snd_hda_intel snd_hda_codec snd_hwdep snd_pcm snd_seq_midi snd_rawmidi snd_seq_midi_event snd_seq snd_timer snd_seq_device snd sis_agp psmouse serio_raw soundcore snd_page_alloc shpchp agpgart lp parport 8139too 8139cp sata_sis mii [last unloaded: hw1] [ 1620.965147] Pid: 0, comm: swapper Tainted: G D 2.6.35-22-generic #33-Ubuntu [ 1620.965150] Call Trace: [ 1620.965160] [<c014ac52>] warn_slowpath_common+0x72/0xa0 [ 1620.965166] [<c050e62d>] ? dev_watchdog+0x1fd/0x210 [ 1620.965170] [<c050e62d>] ? dev_watchdog+0x1fd/0x210 [ 1620.965175] [<c014ad23>] warn_slowpath_fmt+0x33/0x40 [ 1620.965179] [<c050e62d>] dev_watchdog+0x1fd/0x210 [ 1620.965185] [<c0108a28>] ? sched_clock+0x8/0x10 [ 1620.965191] [<c016bf14>] ? sched_clock_local+0xa4/0x180 [ 1620.965195] [<c050e430>] ? dev_watchdog+0x0/0x210 [ 1620.965200] [<c0157e1f>] call_timer_fn+0x2f/0xf0 [ 1620.965204] [<c0169a5a>] ? hrtimer_run_pending+0x4a/0xe0 [ 1620.965209] [<c0159064>] run_timer_softirq+0x104/0x210 [ 1620.965213] [<c016c121>] ? sched_clock_cpu+0x131/0x190 [ 1620.965217] [<c050e430>] ? dev_watchdog+0x0/0x210 [ 1620.965222] [<c015127c>] __do_softirq+0x9c/0x1b0 [ 1620.965226] [<c0158af3>] ? update_process_times+0x53/0x70 [ 1620.965230] [<c01513d5>] do_softirq+0x45/0x50 [ 1620.965234] [<c0151545>] irq_exit+0x65/0x70 [ 1620.965239] [<c05cf72b>] smp_apic_timer_interrupt+0x5b/0x8a [ 1620.965243] [<c016c1ce>] ? sched_clock_idle_sleep_event+0xe/0x10 [ 1620.965248] [<c05c9535>] apic_timer_interrupt+0x31/0x38 [ 1620.965254] [<c010a766>] ? mwait_idle+0x56/0xb0 [ 1620.965257] [<c0101fcc>] cpu_idle+0x8c/0xd0 [ 1620.965262] [<c05b2431>] rest_init+0x71/0x80 [ 1620.965269] [<c081981a>] start_kernel+0x36e/0x374 [ 1620.965273] [<c08199dd>] ? pass_all_bootoptions+0x0/0xa [ 1620.965277] [<c08190d7>] i386_start_kernel+0xd7/0xdf [ 1620.965280] ---[ end trace babb4642fde28353 ]--- Cloud you please give me some help? -- Thanks Harry Wei