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Message-ID: <20080506053748.GC9443@linux.vnet.ibm.com>
Date: Mon, 5 May 2008 22:37:48 -0700
From: "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To: Gautham R Shenoy <ego@...ibm.com>
Cc: linux-kernel@...r.kernel.org, mathieu.desnoyers@...ymtl.ca,
mingo@...e.hu, akpm@...ux-foundation.org, hch@...radead.org,
mmlnx@...ibm.com, dipankar@...ibm.com, dsmith@...hat.com,
rostedt@...dmis.org, adrian.bunk@...ial.fi, a.p.zijlstra@...llo.nl,
niv@...ibm.com, dvhltc@...ibm.com, rusty@....ibm.com,
jkenisto@...ux.vnet.ibm.com, oleg@...sign.ru,
jamesclhuang@...oo.com
Subject: Re: [PATCH 3/5] Add rcu_barrier_sched() and rcu_barrier_bh()
On Mon, May 05, 2008 at 11:12:11PM +0530, Gautham R Shenoy wrote:
> On Mon, May 05, 2008 at 07:47:51AM -0700, Paul E. McKenney wrote:
> > On Mon, May 05, 2008 at 02:52:40PM +0530, Gautham R Shenoy wrote:
> > > On Mon, Apr 21, 2008 at 05:47:43PM -0700, Paul E. McKenney wrote:
> > > > Add rcu_barrier_sched() and rcu_barrier_bh(). With these in place,
> > > > rcutorture no longer gives the occasional oops when repeatedly starting
> > > > and stopping torturing rcu_bh. Also adds the API needed to flush out
> > > > pre-existing call_rcu_sched() callbacks.
> >
> > Thank you again for looking it over!
> >
> > > > Signed-off-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
> > > > Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
> > > > ---
> > > >
> > > > include/linux/rcupdate.h | 2 +
> > > > kernel/rcupdate.c | 55 +++++++++++++++++++++++++++++++++++++++++------
> > > > 2 files changed, 51 insertions(+), 6 deletions(-)
> > > >
> > > > diff -urpNa -X dontdiff linux-2.6.25-C2-rcuclassic-fixes/include/linux/rcupdate.h linux-2.6.25-C3-rcu_barrier_sched/include/linux/rcupdate.h
> > > > --- linux-2.6.25-C2-rcuclassic-fixes/include/linux/rcupdate.h 2008-04-17 08:10:33.000000000 -0700
> > > > +++ linux-2.6.25-C3-rcu_barrier_sched/include/linux/rcupdate.h 2008-04-21 11:33:07.000000000 -0700
> > > > @@ -260,6 +260,8 @@ extern void call_rcu_bh(struct rcu_head
> > > > /* Exported common interfaces */
> > > > extern void synchronize_rcu(void);
> > > > extern void rcu_barrier(void);
> > > > +extern void rcu_barrier_bh(void);
> > > > +extern void rcu_barrier_sched(void);
> > > > extern long rcu_batches_completed(void);
> > > > extern long rcu_batches_completed_bh(void);
> > > >
> > > > diff -urpNa -X dontdiff linux-2.6.25-C2-rcuclassic-fixes/kernel/rcupdate.c linux-2.6.25-C3-rcu_barrier_sched/kernel/rcupdate.c
> > > > --- linux-2.6.25-C2-rcuclassic-fixes/kernel/rcupdate.c 2008-04-17 08:10:33.000000000 -0700
> > > > +++ linux-2.6.25-C3-rcu_barrier_sched/kernel/rcupdate.c 2008-04-21 11:33:08.000000000 -0700
> > > > @@ -45,6 +45,12 @@
> > > > #include <linux/mutex.h>
> > > > #include <linux/module.h>
> > > >
> > > > +enum rcu_barrier {
> > > > + RCU_BARRIER_STD,
> > > STD: Standard, I take it ?
> >
> > Yep. Could say just "RCU_BARRIER", or perhaps "RCU_BARRIER_CLASSIC".
> > Or comment each with the primitive they go with, perhaps better.
>
> A simple RCU_BARRIER should do I guess, since the corresponding
> API is rcu_barrier(). With comments, that'll be even better :-)
Fair enough! ;-)
Thanx, Paul
> --
> Thanks and Regards
> gautham.
>
> >
> > > > + RCU_BARRIER_BH,
> > > > + RCU_BARRIER_SCHED,
> > > > +};
> > > > +
> > > > static DEFINE_PER_CPU(struct rcu_head, rcu_barrier_head) = {NULL};
> > > > static atomic_t rcu_barrier_cpu_count;
> > > > static DEFINE_MUTEX(rcu_barrier_mutex);
> > > > @@ -83,19 +89,30 @@ static void rcu_barrier_callback(struct
> > > > /*
> > > > * Called with preemption disabled, and from cross-cpu IRQ context.
> > > > */
> > > > -static void rcu_barrier_func(void *notused)
> > > > +static void rcu_barrier_func(void *type)
> > > > {
> > > > int cpu = smp_processor_id();
> > > > struct rcu_head *head = &per_cpu(rcu_barrier_head, cpu);
> > > >
> > > > atomic_inc(&rcu_barrier_cpu_count);
> > > > - call_rcu(head, rcu_barrier_callback);
> > > > + switch ((enum rcu_barrier)type) {
> > > > + case RCU_BARRIER_STD:
> > > > + call_rcu(head, rcu_barrier_callback);
> > > > + break;
> > > > + case RCU_BARRIER_BH:
> > > > + call_rcu_bh(head, rcu_barrier_callback);
> > > > + break;
> > > > + case RCU_BARRIER_SCHED:
> > > > + call_rcu_sched(head, rcu_barrier_callback);
> > > > + break;
> > > > + }
> > > > }
> > > >
> > > > -/**
> > > > - * rcu_barrier - Wait until all the in-flight RCUs are complete.
> > > > +/*
> > > > + * Orchestrate the specified type of RCU barrier, waiting for all
> > > > + * RCU callbacks of the specified type to complete.
> > > > */
> > > > -void rcu_barrier(void)
> > > > +static void _rcu_barrier(enum rcu_barrier type)
> > > > {
> > > > BUG_ON(in_interrupt());
> > > > /* Take cpucontrol mutex to protect against CPU hotplug */
> > > > @@ -111,13 +128,39 @@ void rcu_barrier(void)
> > > > * until all the callbacks are queued.
> > > > */
> > > > rcu_read_lock();
> > > > - on_each_cpu(rcu_barrier_func, NULL, 0, 1);
> > > > + on_each_cpu(rcu_barrier_func, (void *)type, 0, 1);
> > > > rcu_read_unlock();
> > > > wait_for_completion(&rcu_barrier_completion);
> > > > mutex_unlock(&rcu_barrier_mutex);
> > > > }
> > > > +
> > > > +/**
> > > > + * rcu_barrier - Wait until all in-flight call_rcu() callbacks complete.
> > > > + */
> > > > +void rcu_barrier(void)
> > > > +{
> > > > + _rcu_barrier(RCU_BARRIER_STD);
> > > > +}
> > > > EXPORT_SYMBOL_GPL(rcu_barrier);
> > > >
> > > > +/**
> > > > + * rcu_barrier_bh - Wait until all in-flight call_rcu_bh() callbacks complete.
> > > > + */
> > > > +void rcu_barrier_bh(void)
> > > > +{
> > > > + _rcu_barrier(RCU_BARRIER_BH);
> > > > +}
> > > > +EXPORT_SYMBOL_GPL(rcu_barrier_bh);
> > > > +
> > > > +/**
> > > > + * rcu_barrier_sched - Wait for in-flight call_rcu_sched() callbacks.
> > > > + */
> > > > +void rcu_barrier_sched(void)
> > > > +{
> > > > + _rcu_barrier(RCU_BARRIER_SCHED);
> > > > +}
> > > > +EXPORT_SYMBOL_GPL(rcu_barrier_sched);
> > > > +
> > > > void __init rcu_init(void)
> > > > {
> > > > __rcu_init();
> > >
> > > --
> > > Thanks and Regards
> > > gautham
--
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