doc: Add rcutree.kthread_prio pointer to stallwarn.txt

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

View File

@ -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
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
interval between successive pairs of interrupts. This can
prevent RCU's kthreads and softirq handlers from running.