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 4/8] rcu: Ensure that ->rcu_urgent_qs is set before resched IPI
Date: Wed, 2 Oct 2019 18:33:01 -0700 [thread overview]
Message-ID: <20191003013305.12854-4-paulmck@kernel.org> (raw)
In-Reply-To: <20191003013243.GA12705@paulmck-ThinkPad-P72>
From: "Joel Fernandes (Google)" <joel@joelfernandes.org>
The RCU-specific resched_cpu() function sends a resched IPI to the
specified CPU, which can be used to force the tick on for a given
nohz_full CPU. This is needed when this nohz_full CPU is looping in the
kernel while blocking the current grace period. However, for the tick
to actually be forced on in all cases, that CPU's rcu_data structure's
->rcu_urgent_qs flag must be set beforehand. This commit therefore
causes rcu_implicit_dynticks_qs() to set this flag prior to invoking
resched_cpu() on a holdout nohz_full CPU.
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
---
kernel/rcu/tree.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 8110514..0d83b19 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -1073,6 +1073,7 @@ static int rcu_implicit_dynticks_qs(struct rcu_data *rdp)
if (tick_nohz_full_cpu(rdp->cpu) &&
time_after(jiffies,
READ_ONCE(rdp->last_fqs_resched) + jtsq * 3)) {
+ WRITE_ONCE(*ruqp, true);
resched_cpu(rdp->cpu);
WRITE_ONCE(rdp->last_fqs_resched, jiffies);
}
--
2.9.5
next prev parent reply other threads:[~2019-10-03 1:33 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-03 1:32 [PATCH tip/core/rcu 0/8] Fixes for v5.5 Paul E. McKenney
2019-10-03 1:32 ` [PATCH tip/core/rcu 1/8] rcu: Remove unused function hlist_bl_del_init_rcu() paulmck
2019-10-03 1:32 ` [PATCH tip/core/rcu 2/8] rcu: Several rcu_segcblist functions can be static paulmck
2019-10-03 1:33 ` [PATCH tip/core/rcu 3/8] workqueue: Convert for_each_wq to use built-in list check paulmck
2019-10-03 1:33 ` paulmck [this message]
2019-10-03 11:43 ` [PATCH tip/core/rcu 4/8] rcu: Ensure that ->rcu_urgent_qs is set before resched IPI Steven Rostedt
2019-10-03 13:45 ` Paul E. McKenney
2019-10-03 1:33 ` [PATCH tip/core/rcu 5/8] rcu: Remove obsolete descriptions for rcu_barrier tracepoint paulmck
2019-10-03 1:33 ` [PATCH tip/core/rcu 6/8] rcu: Update descriptions for rcu_nocb_wake tracepoint paulmck
2019-10-03 1:33 ` [PATCH tip/core/rcu 7/8] rcu: Update descriptions for rcu_future_grace_period tracepoint paulmck
2019-10-03 1:33 ` [PATCH tip/core/rcu 8/8] rcu: Fix uninitialized variable in nocb_gp_wait() paulmck
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