linux/Documentation/clearing-warn-once.txt
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   1Clearing WARN_ONCE
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   4WARN_ONCE / WARN_ON_ONCE / printk_once only emit a message once.
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   6echo 1 > /sys/kernel/debug/clear_warn_once
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   8clears the state and allows the warnings to print once again.
   9This can be useful after test suite runs to reproduce problems.
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