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    Subject[tip:x86/urgent] x86: MCE: make cmci_discover_lock irq-safe
    Commit-ID:  e5299926d7459d9fa7c7f856983147817aedb10e
    Gitweb: http://git.kernel.org/tip/e5299926d7459d9fa7c7f856983147817aedb10e
    Author: Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>
    AuthorDate: Fri, 8 May 2009 17:28:40 +0900
    Committer: Ingo Molnar <mingo@elte.hu>
    CommitDate: Fri, 8 May 2009 11:03:26 +0200

    x86: MCE: make cmci_discover_lock irq-safe

    Lockdep reports the warning below when Li tries to offline one cpu:

    [ 110.835487] =================================
    [ 110.835616] [ INFO: inconsistent lock state ]
    [ 110.835688] 2.6.30-rc4-00336-g8c9ed89 #52
    [ 110.835757] ---------------------------------
    [ 110.835828] inconsistent {HARDIRQ-ON-W} -> {IN-HARDIRQ-W} usage.
    [ 110.835908] swapper/0 [HC1[1]:SC0[0]:HE0:SE1] takes:
    [ 110.835982] (cmci_discover_lock){?.+...}, at: [<ffffffff80236dc0>] cmci_clear+0x30/0x9b

    cmci_clear() can be called via smp_call_function_single().

    It is better to disable interrupt while holding cmci_discover_lock,
    to turn it into an irq-safe lock - we can deadlock otherwise.

    [ Impact: fix possible deadlock in the MCE code ]

    Reported-by: Shaohua Li <shaohua.li@intel.com>
    Signed-off-by: Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>
    Cc: Andi Kleen <andi@firstfloor.org>
    Cc: Andrew Morton <akpm@linux-foundation.org>
    LKML-Reference: <4A03ED38.8000700@jp.fujitsu.com>
    Signed-off-by: Ingo Molnar <mingo@elte.hu>
    Reported-by: Shaohua Li<shaohua.li@intel.com>


    ---
    arch/x86/kernel/cpu/mcheck/mce_intel_64.c | 10 ++++++----
    1 files changed, 6 insertions(+), 4 deletions(-)

    diff --git a/arch/x86/kernel/cpu/mcheck/mce_intel_64.c b/arch/x86/kernel/cpu/mcheck/mce_intel_64.c
    index d6b72df..cef3ee3 100644
    --- a/arch/x86/kernel/cpu/mcheck/mce_intel_64.c
    +++ b/arch/x86/kernel/cpu/mcheck/mce_intel_64.c
    @@ -151,10 +151,11 @@ static void print_update(char *type, int *hdr, int num)
    static void cmci_discover(int banks, int boot)
    {
    unsigned long *owned = (void *)&__get_cpu_var(mce_banks_owned);
    + unsigned long flags;
    int hdr = 0;
    int i;

    - spin_lock(&cmci_discover_lock);
    + spin_lock_irqsave(&cmci_discover_lock, flags);
    for (i = 0; i < banks; i++) {
    u64 val;

    @@ -184,7 +185,7 @@ static void cmci_discover(int banks, int boot)
    WARN_ON(!test_bit(i, __get_cpu_var(mce_poll_banks)));
    }
    }
    - spin_unlock(&cmci_discover_lock);
    + spin_unlock_irqrestore(&cmci_discover_lock, flags);
    if (hdr)
    printk(KERN_CONT "\n");
    }
    @@ -211,13 +212,14 @@ void cmci_recheck(void)
    */
    void cmci_clear(void)
    {
    + unsigned long flags;
    int i;
    int banks;
    u64 val;

    if (!cmci_supported(&banks))
    return;
    - spin_lock(&cmci_discover_lock);
    + spin_lock_irqsave(&cmci_discover_lock, flags);
    for (i = 0; i < banks; i++) {
    if (!test_bit(i, __get_cpu_var(mce_banks_owned)))
    continue;
    @@ -227,7 +229,7 @@ void cmci_clear(void)
    wrmsrl(MSR_IA32_MC0_CTL2 + i, val);
    __clear_bit(i, __get_cpu_var(mce_banks_owned));
    }
    - spin_unlock(&cmci_discover_lock);
    + spin_unlock_irqrestore(&cmci_discover_lock, flags);
    }

    /*

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