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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 05/12] stop_machine: EXP Provide RCU quiescent state in multi_cpu_stop()
Date: Wed,  2 Oct 2019 18:38:56 -0700	[thread overview]
Message-ID: <20191003013903.13079-5-paulmck@kernel.org> (raw)
In-Reply-To: <20191003013834.GA12927@paulmck-ThinkPad-P72>

From: "Paul E. McKenney" <paulmck@linux.ibm.com>

When multi_cpu_stop() loops waiting for other tasks, it can trigger an RCU
CPU stall warning.  This can be misleading because what is instead needed
is information on whatever task is blocking multi_cpu_stop().  This commit
therefore inserts an RCU quiescent state into the multi_cpu_stop()
function's waitloop.

Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
---
 include/linux/rcutree.h | 1 +
 kernel/rcu/tree.c       | 2 +-
 kernel/stop_machine.c   | 1 +
 3 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/include/linux/rcutree.h b/include/linux/rcutree.h
index 18b1ed9..c5147de 100644
--- a/include/linux/rcutree.h
+++ b/include/linux/rcutree.h
@@ -37,6 +37,7 @@ void kfree_call_rcu(struct rcu_head *head, rcu_callback_t func);
 
 void rcu_barrier(void);
 bool rcu_eqs_special_set(int cpu);
+void rcu_momentary_dyntick_idle(void);
 unsigned long get_state_synchronize_rcu(void);
 void cond_synchronize_rcu(unsigned long oldstate);
 
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index db673ae..f708d54 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -364,7 +364,7 @@ bool rcu_eqs_special_set(int cpu)
  *
  * The caller must have disabled interrupts and must not be idle.
  */
-static void __maybe_unused rcu_momentary_dyntick_idle(void)
+void rcu_momentary_dyntick_idle(void)
 {
 	int special;
 
diff --git a/kernel/stop_machine.c b/kernel/stop_machine.c
index c7031a2..34c4f11 100644
--- a/kernel/stop_machine.c
+++ b/kernel/stop_machine.c
@@ -233,6 +233,7 @@ static int multi_cpu_stop(void *data)
 			 */
 			touch_nmi_watchdog();
 		}
+		rcu_momentary_dyntick_idle();
 	} while (curstate != MULTI_STOP_EXIT);
 
 	local_irq_restore(flags);
-- 
2.9.5


  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 ` paulmck [this message]
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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