From: Paul E. McKenney <paulmck@kernel.org>
Date: Thu, 25 Mar 2021 00:08:48 +0000 (-0700)
Subject: rcu-tasks: Make ksoftirqd provide RCU Tasks quiescent states
X-Git-Tag: v5.14-rc1~78^2^8~1
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=cf868c2af244417ed276ba7f716b980841a71340;p=thirdparty%2Flinux.git

rcu-tasks: Make ksoftirqd provide RCU Tasks quiescent states

Heavy networking load can cause a CPU to execute continuously and
indefinitely within ksoftirqd, in which case there will be no voluntary
task switches and thus no RCU-tasks quiescent states.  This commit
therefore causes the exiting rcu_softirq_qs() to provide an RCU-tasks
quiescent state.

This of course means that __do_softirq() and its callers cannot be
invoked from within a tracing trampoline.

Reported-by: Toke Høiland-Jørgensen <toke@redhat.com>
Tested-by: Toke Høiland-Jørgensen <toke@redhat.com>
Reviewed-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
---

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 8e78b2430c168..f4daa4e60b14c 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -242,6 +242,7 @@ void rcu_softirq_qs(void)
 {
 	rcu_qs();
 	rcu_preempt_deferred_qs(current);
+	rcu_tasks_qs(current, false);
 }
 
 /*