linux-kernel - Re: [PATCH rcu 1/2] docs: Add documentation for rude and trace RCU flavors

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Message-ID: <20220420144309.69c6b8d1@gandalf.local.home>
Date:   Wed, 20 Apr 2022 14:43:09 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     "Paul E. McKenney" <paulmck@...nel.org>
Cc:     rcu@...r.kernel.org, linux-kernel@...r.kernel.org,
        kernel-team@...com
Subject: Re: [PATCH rcu 1/2] docs: Add documentation for rude and trace RCU
 flavors

On Wed, 20 Apr 2022 11:37:26 -0700
"Paul E. McKenney" <paulmck@...nel.org> wrote:

> The original purpose of RCU Tasks Rude was to deal with the idle tasks,
> given that RCU Tasks dealt only with the non-idle tasks.
> 
> Or is there a trick that I missed?

It use to be that ftrace trampolines could be called from all sorts of
locations until Peter introduced the "noinstr" annotation that causes
objtool to fail to build when tracing happens there. If that prevents
ftrace from happening in that idle case where RCU tasks can not handle it,
then it may be that we can simply switch ftrace to the RCU tasks and get
rid of rude. ?

-- Steve