Date: Wed, 1 Jul 2015 12:12:21 +0200
From: Peter Zijlstra <peterz@infradead.org>
To: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: Josh Triplett <josh@joshtriplett.org>, linux-kernel@vger.kernel.org,
        mingo@kernel.org, laijs@cn.fujitsu.com, dipankar@in.ibm.com,
        akpm@linux-foundation.org, mathieu.desnoyers@efficios.com,
        tglx@linutronix.de, rostedt@goodmis.org, dhowells@redhat.com,
        edumazet@google.com, dvhart@linux.intel.com, fweisbec@gmail.com,
        oleg@redhat.com, bobby.prani@gmail.com
Subject: Re: [PATCH RFC tip/core/rcu 0/5] Expedited grace periods encouraging
 normal ones
Message-ID: <20150701101221.GS19282@twins.programming.kicks-ass.net>
References: <20150630214805.GA7795@linux.vnet.ibm.com>
 <20150630220014.GA10916@cloud>
 <20150630221224.GQ3717@linux.vnet.ibm.com>
 <20150630234633.GA11450@cloud>
 <20150701001558.GU3717@linux.vnet.ibm.com>
 <20150701004214.GA30853@x>
 <20150701033701.GV3717@linux.vnet.ibm.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20150701033701.GV3717@linux.vnet.ibm.com>
User-Agent: Mutt/1.5.21 (2012-12-30)
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 717
Lines: 15

On Tue, Jun 30, 2015 at 08:37:01PM -0700, Paul E. McKenney wrote:
> > Wait, what?  Why is anything using traditional (non-S) RCU while *any*
> > lock is held?
> 
> In their defense, it is a sleeplock that is never taken except when
> rearranging networking configuration.  Sometimes they need a grace period
> under the lock.  So synchronize_net() checks to see if RTNL is held, and
> does a synchronize_rcu_expedited() if so and a synchronize_rcu() if not.

Sounds vile.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/