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authorPaul E. McKenney <paulmck@kernel.org>2019-11-04 08:22:45 -0800
committerPaul E. McKenney <paulmck@kernel.org>2020-01-24 10:27:33 -0800
commitc51f83c315c392d9776c33eb16a2fe1349d65c7f (patch)
treec0ae69a187c5acd5314516670f1b58140ca38ebb /kernel/rcu
parentrcu: Clear ->rcu_read_unlock_special only once (diff)
downloadlinux-dev-c51f83c315c392d9776c33eb16a2fe1349d65c7f.tar.xz
linux-dev-c51f83c315c392d9776c33eb16a2fe1349d65c7f.zip
rcu: Use READ_ONCE() for ->expmask in rcu_read_unlock_special()
The rcu_node structure's ->expmask field is updated only when holding the ->lock, but is also accessed locklessly. This means that all ->expmask updates must use WRITE_ONCE() and all reads carried out without holding ->lock must use READ_ONCE(). This commit therefore changes the lockless ->expmask read in rcu_read_unlock_special() to use READ_ONCE(). Reported-by: syzbot+99f4ddade3c22ab0cf23@syzkaller.appspotmail.com Signed-off-by: Paul E. McKenney <paulmck@kernel.org> Acked-by: Marco Elver <elver@google.com>
Diffstat (limited to 'kernel/rcu')
-rw-r--r--kernel/rcu/tree_plugin.h2
1 files changed, 1 insertions, 1 deletions
diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index c3a32717c42d..698a7f195f88 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -599,7 +599,7 @@ static void rcu_read_unlock_special(struct task_struct *t)
struct rcu_node *rnp = rdp->mynode;
exp = (t->rcu_blocked_node && t->rcu_blocked_node->exp_tasks) ||
- (rdp->grpmask & rnp->expmask) ||
+ (rdp->grpmask & READ_ONCE(rnp->expmask)) ||
tick_nohz_full_cpu(rdp->cpu);
// Need to defer quiescent state until everything is enabled.
if (irqs_were_disabled && use_softirq &&