From: Paul E. McKenney Date: Mon, 8 Jul 2019 15:01:50 +0000 (-0700) Subject: doc: Add rcutree.kthread_prio pointer to stallwarn.txt X-Git-Url: http://git.lede-project.org./?a=commitdiff_plain;h=0500873de968df6fdef5752d7bbdca317ddc220b;p=openwrt%2Fstaging%2Fblogic.git 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 --- diff --git a/Documentation/RCU/stallwarn.txt b/Documentation/RCU/stallwarn.txt index 13e88fc00f01..f48f4621ccbc 100644 --- a/Documentation/RCU/stallwarn.txt +++ b/Documentation/RCU/stallwarn.txt @@ -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.