Commit 69cdea87 authored by Frederic Weisbecker's avatar Frederic Weisbecker Committed by Paul E. McKenney
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rcu/nocb: Shutdown nocb timer on de-offloading 



This commit ensures that the nocb timer is shut down before reaching the
final de-offloaded state.  The key goal is to prevent the timer handler
from manipulating the callbacks without the protection of the nocb locks.

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: default avatarPaul E. McKenney <paulmck@kernel.org>
Tested-by: default avatarBoqun Feng <boqun.feng@gmail.com>
Signed-off-by: default avatarFrederic Weisbecker <frederic@kernel.org>
Signed-off-by: default avatarPaul E. McKenney <paulmck@kernel.org>
parent 254e11ef

kernel/rcu/tree.h

+1 −0
Original line number Diff line number Diff line
@@ -257,6 +257,7 @@ struct rcu_data { 
};



/* Values for nocb_defer_wakeup field in struct rcu_data. */

#define RCU_NOCB_WAKE_OFF	-1

#define RCU_NOCB_WAKE_NOT	0

#define RCU_NOCB_WAKE		1

#define RCU_NOCB_WAKE_FORCE	2

kernel/rcu/tree_plugin.h

+11 −1
Original line number Diff line number Diff line
@@ -1665,6 +1665,8 @@ static void wake_nocb_gp(struct rcu_data *rdp, bool force, 
static void wake_nocb_gp_defer(struct rcu_data *rdp, int waketype,

			       const char *reason)

{

	if (rdp->nocb_defer_wakeup == RCU_NOCB_WAKE_OFF)

		return;

	if (rdp->nocb_defer_wakeup == RCU_NOCB_WAKE_NOT)

		mod_timer(&rdp->nocb_timer, jiffies + 1);

	if (rdp->nocb_defer_wakeup < waketype)
@@ -2243,7 +2245,7 @@ static int rcu_nocb_cb_kthread(void *arg) 
/* Is a deferred wakeup of rcu_nocb_kthread() required? */

static int rcu_nocb_need_deferred_wakeup(struct rcu_data *rdp)

{

	return READ_ONCE(rdp->nocb_defer_wakeup);

	return READ_ONCE(rdp->nocb_defer_wakeup) > RCU_NOCB_WAKE_NOT;

}



/* Do a deferred wakeup of rcu_nocb_kthread(). */
@@ -2337,6 +2339,12 @@ 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);

	WRITE_ONCE(rdp->nocb_defer_wakeup, RCU_NOCB_WAKE_OFF);

	rcu_nocb_unlock_irqrestore(rdp, flags);

	del_timer_sync(&rdp->nocb_timer);



	return ret;

}
@@ -2394,6 +2402,8 @@ static int __rcu_nocb_rdp_offload(struct rcu_data *rdp) 
	 * SEGCBLIST_SOFTIRQ_ONLY mode.

	 */

	raw_spin_lock_irqsave(&rdp->nocb_lock, flags);

	/* Re-enable nocb timer */

	WRITE_ONCE(rdp->nocb_defer_wakeup, RCU_NOCB_WAKE_NOT);

	/*

	 * We didn't take the nocb lock while working on the

	 * rdp->cblist in SEGCBLIST_SOFTIRQ_ONLY mode.