From: "Paul E. McKenney" <paulmck@kernel.org>
To: Frederic Weisbecker <frederic@kernel.org>
Cc: rcu@vger.kernel.org, linux-kernel@vger.kernel.org,
mingo@kernel.org, jiangshanlai@gmail.com, dipankar@in.ibm.com,
akpm@linux-foundation.org, mathieu.desnoyers@efficios.com,
josh@joshtriplett.org, tglx@linutronix.de, peterz@infradead.org,
rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com,
fweisbec@gmail.com, oleg@redhat.com, joel@joelfernandes.org
Subject: Re: [PATCH tip/core/rcu 03/12] rcu: Force on tick when invoking lots of callbacks
Date: Sat, 5 Oct 2019 09:42:14 -0700 [thread overview]
Message-ID: <20191005164214.GI2689@paulmck-ThinkPad-P72> (raw)
In-Reply-To: <20191003140955.GA27003@lenoir>
On Thu, Oct 03, 2019 at 04:10:52PM +0200, Frederic Weisbecker wrote:
> On Wed, Oct 02, 2019 at 06:38:54PM -0700, paulmck@kernel.org wrote:
> > From: "Paul E. McKenney" <paulmck@linux.ibm.com>
> >
> > Callback invocation can run for a significant time period, and within
> > CONFIG_NO_HZ_FULL=y kernels, this period will be devoid of scheduler-clock
> > interrupts. In-kernel execution without such interrupts can cause all
> > manner of malfunction, with RCU CPU stall warnings being but one result.
> >
> > This commit therefore forces scheduling-clock interrupts on whenever more
> > than a few RCU callbacks are invoked. Because offloaded callback invocation
> > can be preempted, this forcing is withdrawn on each context switch. This
> > in turn requires that the loop invoking RCU callbacks reiterate the forcing
> > periodically.
> >
> > [ paulmck: Apply Joel Fernandes TICK_DEP_MASK_RCU->TICK_DEP_BIT_RCU fix. ]
> > Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
> > ---
> > kernel/rcu/tree.c | 4 ++++
> > 1 file changed, 4 insertions(+)
> >
> > diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
> > index 8110514..db673ae 100644
> > --- a/kernel/rcu/tree.c
> > +++ b/kernel/rcu/tree.c
> > @@ -2151,6 +2151,8 @@ static void rcu_do_batch(struct rcu_data *rdp)
> > rcu_nocb_unlock_irqrestore(rdp, flags);
> >
> > /* Invoke callbacks. */
> > + if (IS_ENABLED(CONFIG_NO_HZ_FULL))
>
> No need for the IS_ENABLED(), the API takes care of that.
>
> > + tick_dep_set_task(current, TICK_DEP_BIT_RCU);
> > rhp = rcu_cblist_dequeue(&rcl);
> > for (; rhp; rhp = rcu_cblist_dequeue(&rcl)) {
> > debug_rcu_head_unqueue(rhp);
> > @@ -2217,6 +2219,8 @@ static void rcu_do_batch(struct rcu_data *rdp)
> > /* Re-invoke RCU core processing if there are callbacks remaining. */
> > if (!offloaded && rcu_segcblist_ready_cbs(&rdp->cblist))
> > invoke_rcu_core();
> > + if (IS_ENABLED(CONFIG_NO_HZ_FULL))
>
> Same here.
Good catches! Applied, thank you!
Thanx, Paul
> Thanks.
>
> > + tick_dep_clear_task(current, TICK_DEP_BIT_RCU);
> > }
> >
> > /*
> > --
> > 2.9.5
> >
next prev parent reply other threads:[~2019-10-05 16:42 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-03 1:38 [PATCH tip/core/rcu 0/12] NO_HZ fixes for v5.5 Paul E. McKenney
2019-10-03 1:38 ` [PATCH tip/core/rcu 01/12] nohz: Add TICK_DEP_BIT_RCU paulmck
2019-10-03 1:38 ` [PATCH tip/core/rcu 02/12] time: Export tick start/stop functions for rcutorture paulmck
2019-10-03 1:38 ` [PATCH tip/core/rcu 03/12] rcu: Force on tick when invoking lots of callbacks paulmck
2019-10-03 14:10 ` Frederic Weisbecker
2019-10-05 16:42 ` Paul E. McKenney [this message]
2019-10-03 1:38 ` [PATCH tip/core/rcu 04/12] rcutorture: Force on tick for readers and callback flooders paulmck
2019-10-03 14:14 ` Frederic Weisbecker
2019-10-05 16:52 ` Paul E. McKenney
2019-10-03 1:38 ` [PATCH tip/core/rcu 05/12] stop_machine: EXP Provide RCU quiescent state in multi_cpu_stop() paulmck
2019-10-03 1:38 ` [PATCH tip/core/rcu 06/12] rcu: Make CPU-hotplug removal operations enable tick paulmck
2019-10-03 14:34 ` Frederic Weisbecker
2019-10-05 17:17 ` Paul E. McKenney
2019-10-03 1:38 ` [PATCH tip/core/rcu 07/12] stop_machine: Use {READ,WRITE)_ONCE() for multi_cpu_stop() ->state paulmck
2019-10-03 1:38 ` [PATCH tip/core/rcu 08/12] rcu: Force tick on for nohz_full CPUs not reaching quiescent states paulmck
2019-10-03 14:50 ` Frederic Weisbecker
2019-10-05 17:21 ` Paul E. McKenney
2019-10-03 1:39 ` [PATCH tip/core/rcu 09/12] rcu: Force nohz_full tick on upon irq enter instead of exit paulmck
2019-10-03 1:39 ` [PATCH tip/core/rcu 10/12] rcu: Reset CPU hints when reporting a quiescent state paulmck
2019-10-03 1:39 ` [PATCH tip/core/rcu 11/12] rcu: Confine ->core_needs_qs accesses to the corresponding CPU paulmck
2019-10-03 1:39 ` [PATCH tip/core/rcu 12/12] rcu: Make kernel-mode nohz_full CPUs invoke the RCU core processing paulmck
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