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Commit 2342172f authored by Paul E. McKenney's avatar Paul E. McKenney
Browse files

rcu: Avoid ->dynticks_nesting store tearing 



Although ->dynticks_nesting is updated only by process level, it is
accessed from hardirq to check for interrupt-from-idle quiescent states.
Store tearing is thus possible, so this commit applies WRITE_ONCE()
to ->dynticks_nesting stores.

Signed-off-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
parent 914955e1

kernel/rcu/tree.c

+3 −3
Original line number Diff line number Diff line
@@ -778,7 +778,7 @@ static void rcu_eqs_enter_common(bool user) 
		do_nocb_deferred_wakeup(rdp);

	}

	rcu_prepare_for_idle();

	rdtp->dynticks_nesting = 0;

	WRITE_ONCE(rdtp->dynticks_nesting, 0); /* Avoid irq-access tearing. */

	rcu_dynticks_eqs_enter();

	rcu_dynticks_task_enter();

}
@@ -976,7 +976,7 @@ static void rcu_eqs_exit(bool user) 
		rdtp->dynticks_nesting++;

	} else {

		rcu_eqs_exit_common(1, user);

		rdtp->dynticks_nesting = 1;

		WRITE_ONCE(rdtp->dynticks_nesting, 1);

		WRITE_ONCE(rdtp->dynticks_nmi_nesting, DYNTICK_IRQ_NONIDLE);

	}

}
@@ -3713,7 +3713,7 @@ rcu_init_percpu_data(int cpu, struct rcu_state *rsp) 
	if (rcu_segcblist_empty(&rdp->cblist) && /* No early-boot CBs? */

	    !init_nocb_callback_list(rdp))

		rcu_segcblist_init(&rdp->cblist);  /* Re-enable callbacks. */

	rdp->dynticks->dynticks_nesting = 1;

	rdp->dynticks->dynticks_nesting = 1;	/* CPU not up, no tearing. */

	rcu_dynticks_eqs_online();

	raw_spin_unlock_rcu_node(rnp);		/* irqs remain disabled. */