• Ingo Molnar's avatar
    x86: dumpstack, 64-bit: Disable preemption when walking the IRQ/exception stacks · 67f2de0b
    Ingo Molnar authored
    This warning:
    
    [  847.140022] rb_producer   D 0000000000000000  5928   519      2 0x00000000
    [  847.203627] BUG: using smp_processor_id() in preemptible [00000000] code: khungtaskd/517
    [  847.207360] caller is show_stack_log_lvl+0x2e/0x241
    [  847.210364] Pid: 517, comm: khungtaskd Not tainted 2.6.32-rc8-tip+ #13761
    [  847.213395] Call Trace:
    [  847.215847]  [<ffffffff81413bde>] debug_smp_processor_id+0x1f0/0x20a
    [  847.216809]  [<ffffffff81015eae>] show_stack_log_lvl+0x2e/0x241
    [  847.220027]  [<ffffffff81018512>] show_stack+0x1c/0x1e
    [  847.223365]  [<ffffffff8107b7db>] sched_show_task+0xe4/0xe9
    [  847.226694]  [<ffffffff8112f21f>] check_hung_task+0x140/0x199
    [  847.230261]  [<ffffffff8112f4a8>] check_hung_uninterruptible_tasks+0x1b7/0x20f
    [  847.233371]  [<ffffffff8112f500>] ? watchdog+0x0/0x50
    [  847.236683]  [<ffffffff8112f54e>] watchdog+0x4e/0x50
    [  847.240034]  [<ffffffff810cee56>] kthread+0x97/0x9f
    [  847.243372]  [<ffffffff81012aea>] child_rip+0xa/0x20
    [  847.246690]  [<ffffffff81e43494>] ? restore_args+0x0/0x30
    [  847.250019]  [<ffffffff81e43083>] ? _spin_lock+0xe/0x10
    [  847.253351]  [<ffffffff810cedbf>] ? kthread+0x0/0x9f
    [  847.256833]  [<ffffffff81012ae0>] ? child_rip+0x0/0x20
    
    Happens because on preempt-RCU, khungd calls show_stack() with
    preemption enabled.
    
    Make sure we are not preemptible while walking the IRQ and exception
    stacks on 64-bit. (32-bit stack dumping is preemption safe.)
    Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
    67f2de0b
dumpstack_64.c 7.34 KB