check_hung_uninterruptible_tasks

Name:Check whether a TASK_UNINTERRUPTIBLE does not get woken up for* a really long time (120 seconds). If that happens, print out* a warning.

Proto:static void check_hung_uninterruptible_tasks(unsigned long timeout)

Type:void

Parameter:

Type	Parameter	Name
unsigned long	timeout

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max_count = The number of tasks checked:

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last_break = jiffies

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If test_taint(TAINT_DIE) || did_panic Then Return

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hung_task_show_lock = false

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_read_lock() - mark the beginning of an RCU read-side critical section* When synchronize_rcu() is invoked on one CPU while other CPUs* are within RCU read-side critical sections, then the* synchronize_rcu() is guaranteed to block until after all the other

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Careful: this is a double loop, 'break' won't work as expected. (g, t)

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If Not max_count -- Then Go to unlock

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If These inlines deal with timer wrapping correctly. You are * strongly encouraged to use them* 1. Because people otherwise forget* 2. Because if the timer wrap changes in future you won't have to* alter your driver code.(jiffies, last_break + Limit number of tasks checked in a batch.* This value controls the preemptibility of khungtaskd since preemption* is disabled during the critical section. It also controls the size of* the RCU grace period. So it needs to be upper-bound.) Then

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If Not To avoid extending the RCU grace period for an unbounded amount of time,* periodically exit the critical section and enter a new one.* For preemptible RCU it is sufficient to call rcu_read_unlock in order* to exit the grace period Then Go to unlock

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last_break = jiffies

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If run state == TASK_UNINTERRUPTIBLE Then check_hung_task(t, timeout)

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_read_unlock() - marks the end of an RCU read-side critical section.* In most situations, rcu_read_unlock() is immune from deadlock.* However, in kernels built with CONFIG_RCU_BOOST, rcu_read_unlock()

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If hung_task_show_lock Then debug_show_all_locks()

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If hung_task_call_panic Then

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trigger_all_cpu_backtrace()

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panic - halt the system*@fmt: The text string to print* Display a message, then perform cleanups.* This function never returns.

**Caller**
Name	Describe
watchdog	kthread which checks for tasks stuck in D state

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