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doc: Add rcutree.kthread_prio pointer to stallwarn.txt

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This commit adds mention of the rcutree.kthread_prio kernel boot parameter
to the discussion of how high-priority real-time tasks can result in
RCU CPU stall warnings.  (However, this does not necessarily help when
the high-priority real-time tasks are using dubious deadlines.)

Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
This commit is contained in:
Paul E. McKenney 2019-07-08 08:01:50 -07:00
parent 3545832fc2
commit 0500873de9
1 changed files with 6 additions and 0 deletions
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6
Documentation/RCU/stallwarn.txt
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@ -57,6 +57,12 @@ o A CPU-bound real-time task in a CONFIG_PREEMPT_RT kernel that
CONFIG_PREEMPT_RCU case, you might see stall-warning CONFIG_PREEMPT_RCU case, you might see stall-warning
messages. messages.
You can use the rcutree.kthread_prio kernel boot parameter to
increase the scheduling priority of RCU's kthreads, which can
help avoid this problem. However, please note that doing this
can increase your system's context-switch rate and thus degrade
performance.
o A periodic interrupt whose handler takes longer than the time o A periodic interrupt whose handler takes longer than the time
interval between successive pairs of interrupts. This can interval between successive pairs of interrupts. This can
prevent RCU's kthreads and softirq handlers from running. prevent RCU's kthreads and softirq handlers from running.