rcu: For RCU grace-period kthread starvation, dump last CPU it ran on

mainline inclusion
from mainline-v5.12-rc1
commit 243027a3
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I7OIXK

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=243027a3c80564bf96e40437ffac46efb9f5f2b5



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When the RCU CPU stall-warning code detects that the RCU grace-period
kthread is being starved, it dumps that kthread's stack.  This can
sometimes be useful, but it is also useful to know what is running on the
CPU that this kthread is attempting to run on.  This commit therefore
adds a stack trace of this CPU in order to help track down whatever it
is that might be preventing RCU's grace-period kthread from running.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>