Gitweb:     http://git.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=c...

Commit:     a263898f628dd21e59210b547986c154788f628e

Parent:     57a04513cb35086d54bcb2cb92e6627fc8fa0fae

Author:     Ingo Molnar <mingo@elte.hu>

AuthorDate: Sun Dec 30 11:58:17 2007 +0100

Committer:  Linus Torvalds <torvalds@woody.linux-foundation.org>

CommitDate: Sun Jan 6 12:39:42 2008 -0800
    CPU hotplug: fix cpu_is_offline() on !CONFIG_HOTPLUG_CPU
    make randconfig bootup testing found that the cpufreq code

    crashes on bootup, if the powernow-k8 driver is enabled and

    if maxcpus=1 passed on the boot line to a !CONFIG_HOTPLUG_CPU

    kernel.
    First lockdep found out that there's an inconsistent unlock

    sequence:
     =====================================

     [ BUG: bad unlock balance detected! ]

     -------------------------------------

     swapper/1 is trying to release lock (&per_cpu(cpu_policy_rwsem, cpu)) at:

     [<ffffffff806ffd8e>] unlock_policy_rwsem_write+0x3c/0x42

     but there are no more locks to release!
    Call Trace:

     [<ffffffff806ffd8e>] unlock_policy_rwsem_write+0x3c/0x42

     [<ffffffff80251c29>] print_unlock_inbalance_bug+0x104/0x12c

     [<ffffffff80252f3a>] mark_held_locks+0x56/0x94

     [<ffffffff806ffd8e>] unlock_policy_rwsem_write+0x3c/0x42

     [<ffffffff807008b6>] cpufreq_add_dev+0x2a8/0x5c4

     ...
    then shortly afterwards the cpufreq code crashed on an assert:
     ------------[ cut here ]------------

     kernel BUG at drivers/cpufreq/cpufreq.c:1068!

     invalid opcode: 0000 [1] SMP

     [...]

     Call Trace:

      [<ffffffff805145d6>] sysdev_driver_unregister+0x5b/0x91

      [<ffffffff806ff520>] cpufreq_register_driver+0x15d/0x1a2

      [<ffffffff80cc0596>] powernowk8_init+0x86/0x94

     [...]

     ---[ end trace 1e9219be2b4431de ]---
    the bug was caused by maxcpus=1...
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