From: Steven Rostedt <rostedt@goodmis.org>
To: "Paul E. McKenney" <paulmck@kernel.org>
Cc: linux-kernel@vger.kernel.org,
Madhuparna Bhowmik <madhuparnabhowmik10@gmail.com>,
Ingo Molnar <mingo@redhat.com>,
Joel Fernandes <joel@joelfernandes.org>,
linux-kernel-mentees@lists.linuxfoundation.org
Subject: Re: [Linux-kernel-mentees] [PATCH] tracing: Annotate ftrace_graph_hash pointer with __rcu
Date: Wed, 5 Feb 2020 08:19:21 -0500 [thread overview]
Message-ID: <20200205081921.34b19d9a@oasis.local.home> (raw)
In-Reply-To: <20200205081409.4550aa67@oasis.local.home>
On Wed, 5 Feb 2020 08:14:09 -0500
Steven Rostedt <rostedt@goodmis.org> wrote:
> On Wed, 5 Feb 2020 05:11:10 -0800
> "Paul E. McKenney" <paulmck@kernel.org> wrote:
>
> > I strongly recommend a comment stating why disabling preemption prevents
> > ftrace_graph_hash from going away. I see the synchronize_rcu() after
> > the rcu_assign_pointer() in ftrace_graph_release(), but I don't see
> > anything that waits on CPUs that RCU is not watching.
> >
> > Of course, event tracing -makes- RCU watch when needed, but if that
> > was set up, then lockdep would not have complained.
> >
> > So what am I missing?
>
> Keep looking in your INBOX and look at the patch I asked you to ack or
> complain about ;-)
Actually, looking at the code myself, it appears to be missing the
ftrace_sync. Thus, this is a bug, and requires the ftrace sync, as
synchronize_rcu() is not strong enough here.
Patch in process!
-- Steve
_______________________________________________
Linux-kernel-mentees mailing list
Linux-kernel-mentees@lists.linuxfoundation.org
https://lists.linuxfoundation.org/mailman/listinfo/linux-kernel-mentees
next prev parent reply other threads:[~2020-02-05 13:19 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-01 7:27 [Linux-kernel-mentees] [PATCH] tracing: Annotate ftrace_graph_hash pointer with __rcu Amol Grover
2020-02-03 16:33 ` Joel Fernandes
2020-02-04 10:02 ` Steven Rostedt
2020-02-05 1:01 ` Steven Rostedt
2020-02-05 5:26 ` Amol Grover
2020-02-05 13:11 ` Paul E. McKenney
2020-02-05 13:14 ` Steven Rostedt
2020-02-05 13:19 ` Steven Rostedt [this message]
2020-02-05 13:29 ` Paul E. McKenney
2020-02-05 22:06 ` Joel Fernandes
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20200205081921.34b19d9a@oasis.local.home \
--to=rostedt@goodmis.org \
--cc=joel@joelfernandes.org \
--cc=linux-kernel-mentees@lists.linuxfoundation.org \
--cc=linux-kernel@vger.kernel.org \
--cc=madhuparnabhowmik10@gmail.com \
--cc=mingo@redhat.com \
--cc=paulmck@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).