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rcu/nocb: Flush bypass before setting SEGCBLIST_SOFTIRQ_ONLY

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This commit flushes the bypass queue and sets state to avoid its being
refilled before switching to the final de-offloaded state.  To avoid
refilling, this commit sets SEGCBLIST_SOFTIRQ_ONLY before re-enabling
IRQs.

Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Cc: Joel Fernandes <joel@joelfernandes.org>
Cc: Neeraj Upadhyay <neeraju@codeaurora.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Inspired-by: Paul E. McKenney <paulmck@kernel.org>
Tested-by: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit is contained in:
Frederic Weisbecker 2020-11-13 13:13:24 +01:00 committed by Paul E. McKenney
parent 69cdea873c
commit 314202f84d
1 changed files with 10 additions and 1 deletions
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11
kernel/rcu/tree_plugin.h
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@ -2339,12 +2339,21 @@ static int __rcu_nocb_rdp_deoffload(struct rcu_data *rdp)
swait_event_exclusive(rdp->nocb_state_wq,
!rcu_segcblist_test_flags(cblist, SEGCBLIST_KTHREAD_CB |
SEGCBLIST_KTHREAD_GP));
/* Make sure nocb timer won't stay around */
rcu_nocb_lock_irqsave(rdp, flags);
/* Make sure nocb timer won't stay around */
WRITE_ONCE(rdp->nocb_defer_wakeup, RCU_NOCB_WAKE_OFF);
rcu_nocb_unlock_irqrestore(rdp, flags);
del_timer_sync(&rdp->nocb_timer);
/*
* Flush bypass. While IRQs are disabled and once we set
* SEGCBLIST_SOFTIRQ_ONLY, no callback is supposed to be
* enqueued on bypass.
*/
rcu_nocb_lock_irqsave(rdp, flags);
rcu_nocb_flush_bypass(rdp, NULL, jiffies);
rcu_nocb_unlock_irqrestore(rdp, flags);
return ret;
}