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    Subject[patch 2/2] hung_task: add method to reset detector
    In certain occasions it is possible for a hung task detector
    positive to be false: continuation from a paused VM, for example.

    Add a method to reset detection, similar as is done
    with other kernel watchdogs.

    Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

    Index: kvm/kernel/hung_task.c
    ===================================================================
    --- kvm.orig/kernel/hung_task.c
    +++ kvm/kernel/hung_task.c
    @@ -203,6 +203,14 @@ int proc_dohung_task_timeout_secs(struct
    return ret;
    }

    +static atomic_t reset_hung_task = ATOMIC_INIT(0);
    +
    +void reset_hung_task_detector(void)
    +{
    + atomic_set(&reset_hung_task, 1);
    +}
    +EXPORT_SYMBOL_GPL(reset_hung_task_detector);
    +
    /*
    * kthread which checks for tasks stuck in D state
    */
    @@ -216,6 +224,9 @@ static int watchdog(void *dummy)
    while (schedule_timeout_interruptible(timeout_jiffies(timeout)))
    timeout = sysctl_hung_task_timeout_secs;

    + if (atomic_xchg(&reset_hung_task, 0))
    + continue;
    +
    check_hung_uninterruptible_tasks(timeout);
    }

    Index: kvm/include/linux/sched.h
    ===================================================================
    --- kvm.orig/include/linux/sched.h
    +++ kvm/include/linux/sched.h
    @@ -285,6 +285,14 @@ static inline void lockup_detector_init(
    }
    #endif

    +#ifdef CONFIG_DETECT_HUNG_TASK
    +void reset_hung_task_detector(void);
    +#else
    +static inline void reset_hung_task_detector(void)
    +{
    +}
    +#endif
    +
    /* Attach to any functions which should be ignored in wchan output. */
    #define __sched __attribute__((__section__(".sched.text")))

    Index: kvm/arch/x86/kernel/pvclock.c
    ===================================================================
    --- kvm.orig/arch/x86/kernel/pvclock.c
    +++ kvm/arch/x86/kernel/pvclock.c
    @@ -48,6 +48,7 @@ void pvclock_touch_watchdogs(void)
    touch_softlockup_watchdog_sync();
    clocksource_touch_watchdog();
    rcu_cpu_stall_reset();
    + reset_hung_task_detector();
    }

    static atomic64_t last_value = ATOMIC64_INIT(0);



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