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Commit f7be8209 authored by Paul E. McKenney's avatar Paul E. McKenney
Browse files

rcu: Improve grace-period start logic 



This commit improves grace-period start logic by checking ->gp_flags
under the lock and by issuing a warning if a grace period is already
in progress.

Signed-off-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
parent 272b98c6

kernel/rcutree.c

+12 −5
Original line number Diff line number Diff line
@@ -1297,7 +1297,7 @@ static void note_gp_changes(struct rcu_state *rsp, struct rcu_data *rdp) 
}



/*

 * Initialize a new grace period.

 * Initialize a new grace period.  Return 0 if no grace period required.

 */

static int rcu_gp_init(struct rcu_state *rsp)

{
@@ -1306,10 +1306,18 @@ static int rcu_gp_init(struct rcu_state *rsp) 


	rcu_bind_gp_kthread();

	raw_spin_lock_irq(&rnp->lock);

	if (rsp->gp_flags == 0) {

		/* Spurious wakeup, tell caller to go back to sleep.  */

		raw_spin_unlock_irq(&rnp->lock);

		return 0;

	}

	rsp->gp_flags = 0; /* Clear all flags: New grace period. */



	if (rcu_gp_in_progress(rsp)) {

		/* Grace period already in progress, don't start another.  */

	if (WARN_ON_ONCE(rcu_gp_in_progress(rsp))) {

		/*

		 * Grace period already in progress, don't start another.

		 * Not supposed to be able to happen.

		 */

		raw_spin_unlock_irq(&rnp->lock);

		return 0;

	}
@@ -1474,8 +1482,7 @@ static int __noreturn rcu_gp_kthread(void *arg) 
			wait_event_interruptible(rsp->gp_wq,

						 rsp->gp_flags &

						 RCU_GP_FLAG_INIT);

			if ((rsp->gp_flags & RCU_GP_FLAG_INIT) &&

			    rcu_gp_init(rsp))

			if (rcu_gp_init(rsp))

				break;

			cond_resched();

			flush_signals(current);