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    SubjectRe: [patch 00/61] ANNOUNCE: lock validator -V1

    * Michal Piotrowski <> wrote:

    > On 29/05/06, Ingo Molnar <> wrote:
    > >We are pleased to announce the first release of the "lock dependency
    > >correctness validator" kernel debugging feature, which can be downloaded
    > >from:
    > >
    > >
    > >
    > [snip]
    > I get this while loading cpufreq modules
    > =====================================================
    > [ BUG: possible circular locking deadlock detected! ]
    > -----------------------------------------------------
    > modprobe/1942 is trying to acquire lock:
    > (&anon_vma->lock){--..}, at: [<c10609cf>] anon_vma_link+0x1d/0xc9
    > but task is already holding lock:
    > (&mm->mmap_sem/1){--..}, at: [<c101e5a0>] copy_process+0xbc6/0x1519
    > which lock already depends on the new lock,
    > which could lead to circular deadlocks!

    hm, this one could perhaps be a real bug. Dave: lockdep complains about
    having observed:

    anon_vma->lock => mm->mmap_sem
    mm->mmap_sem => anon_vma->lock

    locking sequences, in the cpufreq code. Is there some special runtime
    behavior that still makes this safe, or is it a real bug?

    > stack backtrace:
    > <c1003f36> show_trace+0xd/0xf <c1004449> dump_stack+0x17/0x19
    > <c103863e> print_circular_bug_tail+0x59/0x64 <c1038e91>
    > __lockdep_acquire+0x848/0xa39
    > <c10394be> lockdep_acquire+0x69/0x82 <c11ed759>
    > __mutex_lock_slowpath+0xd0/0x347

    there's one small detail to improve future lockdep printouts: please set
    CONFIG_STACK_BACKTRACE_COLS=1, so that the backtrace is more readable.
    (i'll change the code to force that when CONFIG_LOCKDEP is enabled)

    > BTW I still must revert lockdep-serial.patch - it doesn't compile on
    > my gcc 4.1.1

    ok, will check this.

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      Last update: 2006-05-30 00:43    [W:0.025 / U:0.208 seconds]
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