From: paulmck@kernel.org
To: rcu@vger.kernel.org
Cc: 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,
"Paul E. McKenney" <paulmck@linux.ibm.com>
Subject: [PATCH tip/core/rcu 09/12] rcu: Force nohz_full tick on upon irq enter instead of exit
Date: Wed, 2 Oct 2019 18:39:00 -0700 [thread overview]
Message-ID: <20191003013903.13079-9-paulmck@kernel.org> (raw)
In-Reply-To: <20191003013834.GA12927@paulmck-ThinkPad-P72>
From: "Paul E. McKenney" <paulmck@linux.ibm.com>
There is interrupt-exit code that forces on the tick for nohz_full CPUs
failing to respond to the current grace period in a timely fashion.
However, this code must compare ->dynticks_nmi_nesting to the value 2
in the interrupt-exit fastpath. This commit therefore moves this code
to the interrupt-entry fastpath, where a lighter-weight comparison to
zero may be used.
Reported-by: Joel Fernandes <joel@joelfernandes.org>
[ 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 | 11 +++++------
1 file changed, 5 insertions(+), 6 deletions(-)
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 621cc06..1601fa6 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -650,12 +650,6 @@ static __always_inline void rcu_nmi_exit_common(bool irq)
*/
if (rdp->dynticks_nmi_nesting != 1) {
trace_rcu_dyntick(TPS("--="), rdp->dynticks_nmi_nesting, rdp->dynticks_nmi_nesting - 2, rdp->dynticks);
- if (tick_nohz_full_cpu(rdp->cpu) &&
- rdp->dynticks_nmi_nesting == 2 &&
- rdp->rcu_urgent_qs && !rdp->rcu_forced_tick) {
- rdp->rcu_forced_tick = true;
- tick_dep_set_cpu(rdp->cpu, TICK_DEP_MASK_RCU);
- }
WRITE_ONCE(rdp->dynticks_nmi_nesting, /* No store tearing. */
rdp->dynticks_nmi_nesting - 2);
return;
@@ -830,6 +824,11 @@ static __always_inline void rcu_nmi_enter_common(bool irq)
rcu_cleanup_after_idle();
incby = 1;
+ } else if (tick_nohz_full_cpu(rdp->cpu) &&
+ rdp->dynticks_nmi_nesting == DYNTICK_IRQ_NONIDLE &&
+ rdp->rcu_urgent_qs && !rdp->rcu_forced_tick) {
+ rdp->rcu_forced_tick = true;
+ tick_dep_set_cpu(rdp->cpu, TICK_DEP_BIT_RCU);
}
trace_rcu_dyntick(incby == 1 ? TPS("Endirq") : TPS("++="),
rdp->dynticks_nmi_nesting,
--
2.9.5
next prev parent reply other threads:[~2019-10-03 1:39 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
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 ` paulmck [this message]
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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