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    Subject[PATCH v2] printk: ignore recursion_bug flag in HW error handle process
    From: ShuoX Liu <shuox.liu@intel.com>

    When MCE happens in printk, we ignore recursion_bug to make sure MCE logs printed out.

    According to Boris' suggestion, we add some helper functions.
    1) hw_error_enter: Call it when specific arch begins to process a hardware error.
    2) hw_error_exit: Call it when specific arch finishes the processing of a hardware error.
    3) in_hw_error():indicates whether HW error handling is in processing.

    Each arch could call the helpers in their arch-dependent HW error handlers.

    Signed-off-by: Yanmin Zhang <yanmin_zhang@linux.intel.com>
    Signed-off-by: ShuoX Liu <shuox.liu@intel.com>
    ---
    arch/x86/include/asm/mce.h | 2 --
    arch/x86/kernel/cpu/mcheck/mce.c | 6 ++----
    include/linux/cpu.h | 17 +++++++++++++++++
    kernel/cpu.c | 3 +++
    kernel/printk.c | 3 ++-
    5 files changed, 24 insertions(+), 7 deletions(-)

    diff --git a/arch/x86/include/asm/mce.h b/arch/x86/include/asm/mce.h
    index 441520e..aeda4cc 100644
    --- a/arch/x86/include/asm/mce.h
    +++ b/arch/x86/include/asm/mce.h
    @@ -187,8 +187,6 @@ int mce_available(struct cpuinfo_x86 *c);
    DECLARE_PER_CPU(unsigned, mce_exception_count);
    DECLARE_PER_CPU(unsigned, mce_poll_count);

    -extern atomic_t mce_entry;
    -
    typedef DECLARE_BITMAP(mce_banks_t, MAX_NR_BANKS);
    DECLARE_PER_CPU(mce_banks_t, mce_poll_banks);

    diff --git a/arch/x86/kernel/cpu/mcheck/mce.c b/arch/x86/kernel/cpu/mcheck/mce.c
    index 2afcbd2..aaf41d2 100644
    --- a/arch/x86/kernel/cpu/mcheck/mce.c
    +++ b/arch/x86/kernel/cpu/mcheck/mce.c
    @@ -61,8 +61,6 @@ int mce_disabled __read_mostly;

    #define SPINUNIT 100 /* 100ns */

    -atomic_t mce_entry;
    -
    DEFINE_PER_CPU(unsigned, mce_exception_count);

    /*
    @@ -1015,7 +1013,7 @@ void do_machine_check(struct pt_regs *regs, long error_code)
    DECLARE_BITMAP(toclear, MAX_NR_BANKS);
    char *msg = "Unknown";

    - atomic_inc(&mce_entry);
    + hw_error_enter();

    this_cpu_inc(mce_exception_count);

    @@ -1143,7 +1141,7 @@ void do_machine_check(struct pt_regs *regs, long error_code)
    mce_report_event(regs);
    mce_wrmsrl(MSR_IA32_MCG_STATUS, 0);
    out:
    - atomic_dec(&mce_entry);
    + hw_error_exit();
    sync_core();
    }
    EXPORT_SYMBOL_GPL(do_machine_check);
    diff --git a/include/linux/cpu.h b/include/linux/cpu.h
    index 7230bb5..beb56d0 100644
    --- a/include/linux/cpu.h
    +++ b/include/linux/cpu.h
    @@ -210,4 +210,21 @@ static inline int disable_nonboot_cpus(void) { return 0; }
    static inline void enable_nonboot_cpus(void) {}
    #endif /* !CONFIG_PM_SLEEP_SMP */

    +/* HW error handle status helpers */
    +extern atomic_t hw_error;
    +static inline void hw_error_enter(void)
    +{
    + atomic_inc(&hw_error);
    +}
    +
    +static inline void hw_error_exit(void)
    +{
    + atomic_dec(&hw_error);
    +}
    +
    +static inline int in_hw_error(void)
    +{
    + return atomic_read(&hw_error);
    +}
    +
    #endif /* _LINUX_CPU_H_ */
    diff --git a/kernel/cpu.c b/kernel/cpu.c
    index 0e6353c..54b9c1f 100644
    --- a/kernel/cpu.c
    +++ b/kernel/cpu.c
    @@ -679,3 +679,6 @@ void init_cpu_online(const struct cpumask *src)
    {
    cpumask_copy(to_cpumask(cpu_online_bits), src);
    }
    +
    +/* hardware error status */
    +atomic_t hw_error __read_mostly = ATOMIC_INIT(0);
    diff --git a/kernel/printk.c b/kernel/printk.c
    index 32462d2..6f0f216 100644
    --- a/kernel/printk.c
    +++ b/kernel/printk.c
    @@ -1295,7 +1295,8 @@ asmlinkage int vprintk_emit(int facility, int level,
    * recursion and return - but flag the recursion so that
    * it can be printed at the next appropriate moment:
    */
    - if (!oops_in_progress && !lockdep_recursing(current)) {
    + if (!oops_in_progress && !in_hw_error()
    + && !lockdep_recursing(current)) {
    recursion_bug = 1;
    goto out_restore_irqs;
    }
    --
    1.7.1

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