Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Date:   Thu, 18 Oct 2018 21:12:45 -0400
From:   Steven Rostedt <rostedt@goodmis.org>
To:     "Paul E. McKenney" <paulmck@linux.ibm.com>
Cc:     Joel Fernandes <joel@joelfernandes.org>,
        Nikolay Borisov <nborisov@suse.com>,
        linux-kernel@vger.kernel.org, Jonathan Corbet <corbet@lwn.net>,
        Josh Triplett <josh@joshtriplett.org>,
        Lai Jiangshan <jiangshanlai@gmail.com>,
        linux-doc@vger.kernel.org,
        Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Subject: Re: [PATCH RFC] doc: rcu: remove obsolete (non-)requirement about
 disabling preemption
Message-ID: <20181018211245.10baf496@vmware.local.home>
In-Reply-To: <20181019001932.GR2674@linux.ibm.com>
References: <20181015201556.GA43575@joelaf.mtv.corp.google.com>
        <20181015210856.GE2674@linux.ibm.com>
        <20181016112611.GA27405@linux.ibm.com>
        <20181016204122.GA8176@joelaf.mtv.corp.google.com>
        <20181017161100.GP2674@linux.ibm.com>
        <20181017181505.GC107185@joelaf.mtv.corp.google.com>
        <20181017203324.GS2674@linux.ibm.com>
        <20181018020751.GB99677@joelaf.mtv.corp.google.com>
        <20181018144637.GD2674@linux.ibm.com>
        <20181019000350.GB89903@joelaf.mtv.corp.google.com>
        <20181019001932.GR2674@linux.ibm.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Thu, 18 Oct 2018 17:19:32 -0700
"Paul E. McKenney" <paulmck@linux.ibm.com> wrote:

> I figured that whoever calls preempt_enable_no_resched() is taking the
> responsibility for permitting preemption in the near future, and if they
> fail to do so, they will get called on it.  Hard to hide from the latency
> tracer, after all.  ;-)

Correct, and doing a search of preempt_enable_no_resched() I see
there's one in the ftrace ring buffer code, that was added a long time
ago (2008) to fix a recursion bug that no longer exists, and this now
can leak a preemption point.

I'll have to go fix that :-(

-- Steve