Commit-ID: 2342172fd6c148506456862d795c7f155baf6797
Gitweb: https://git.kernel.org/tip/2342172fd6c148506456862d795c7f155baf6797
Author: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
AuthorDate: Thu, 5 Oct 2017 15:03:10 -0700
Committer: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
CommitDate: Tue, 28 Nov 2017 15:51:20 -0800
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: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
---
kernel/rcu/tree.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 80cada1..b2ded4d 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -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. */
--
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