linux-kernel - Re: call_rcu from trace

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Message-ID: <20150616160716.GM3913@linux.vnet.ibm.com>
Date:	Tue, 16 Jun 2015 09:07:16 -0700
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	Daniel Wagner <wagi@...om.org>,
	Alexei Starovoitov <ast@...mgrid.com>,
	Daniel Wagner <daniel.wagner@...-carit.de>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: call_rcu from trace_preempt

On Tue, Jun 16, 2015 at 11:43:42AM -0400, Steven Rostedt wrote:
> On Tue, 16 Jun 2015 07:16:26 -0700
> "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com> wrote:
> 
> > > Just for the record: Using a thread for freeing the memory is curing the
> > > problem without the need to modify rcu_is_watching.
> > 
> > I must confess to liking this approach better than guaranteeing full-up
> > reentrancy in call_rcu() and kfree_rcu().  ;-)
> 
> Then reentrancy must be really bad if you prefer a spinning thread that
> polls constantly just to free an item ;-)

I was (perhaps naively) assuming that they would use a less aggressive
approach at some point.  ;-)

							Thanx, Paul

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