• Konrad Rzeszutek Wilk's avatar
    cpuidle: Check for dev before deregistering it. · 813e8e3d
    Konrad Rzeszutek Wilk authored
    
    
    If not, we could end up in the unfortunate situation where
    we dereference a NULL pointer b/c we have cpuidle disabled.
    
    This is the case when booting under Xen (which uses the
    ACPI P/C states but disables the CPU idle driver) - and can
    be easily reproduced when booting with cpuidle.off=1.
    
    BUG: unable to handle kernel NULL pointer dereference at           (null)
    IP: [<ffffffff8156db4a>] cpuidle_unregister_device+0x2a/0x90
    .. snip..
    Call Trace:
     [<ffffffff813b15b4>] acpi_processor_power_exit+0x3c/0x5c
     [<ffffffff813af0a9>] acpi_processor_stop+0x61/0xb6
     [<ffffffff814215bf>] __device_release_driver+0fffff81421653>] device_release_driver+0x23/0x30
     [<ffffffff81420ed8>] bus_remove_device+0x108/0x180
     [<ffffffff8141d9d9>] device_del+0x129/0x1c0
     [<ffffffff813cb4b0>] ? unregister_xenbus_watch+0x1f0/0x1f0
     [<ffffffff8141da8e>] device_unregister+0x1e/0x60
     [<ffffffff814243e9>] unregister_cpu+0x39/0x60
     [<ffffffff81019e03>] arch_unregister_cpu+0x23/0x30
     [<ffffffff813c3c51>] handle_vcpu_hotplug_event+0xc1/0xe0
     [<ffffffff813cb4f5>] xenwatch_thread+0x45/0x120
     [<ffffffff810af010>] ? abort_exclusive_wait+0xb0/0xb0
     [<ffffffff8108ec42>] kthread+0xd2/0xf0
     [<ffffffff8108eb70>] ? kthread_create_on_node+0x180/0x180
     [<ffffffff816ce17c>] ret_from_fork+0x7c/0xb0
     [<ffffffff8108eb70>] ? kthread_create_on_node+0x180/0x180
    
    This problem also appears in 3.12 and could be a candidate for backport.
    
    Signed-off-by: default avatarKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>
    Cc: All applicable <stable@vger.kernel.org>
    Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
    813e8e3d