srcu: Check for concurrent updates of heuristics

SRCU maintains the ->srcu_n_exp_nodelay and ->reschedule_count values
to guide heuristics governing auto-expediting of normal SRCU grace
periods and grace-period-state-machine delays.  This commit adds KCSAN
ASSERT_EXCLUSIVE_WRITER() calls to check for concurrent updates to
these fields.

Signed-off-by: "Paul E. McKenney" <paulmck@kernel.org>
Signed-off-by: Neeraj Upadhyay <neeraj.upadhyay@kernel.org>

diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c
index 6fd9c914ce64282c5a864447594a909586350cab..aaee09a6748c2fcc05493a38d0adfb31900ed073 100644 (file)
--- a/kernel/rcu/srcutree.c
+++ b/kernel/rcu/srcutree.c
@@ -629,6 +629,7 @@ static unsigned long srcu_get_delay(struct srcu_struct *ssp)
                if (time_after(j, gpstart))
                        jbase += j - gpstart;
                if (!jbase) {
+                       ASSERT_EXCLUSIVE_WRITER(sup->srcu_n_exp_nodelay);
                        WRITE_ONCE(sup->srcu_n_exp_nodelay, READ_ONCE(sup->srcu_n_exp_nodelay) + 1);
                        if (READ_ONCE(sup->srcu_n_exp_nodelay) > srcu_max_nodelay_phase)
                                jbase = 1;
@@ -1819,6 +1820,7 @@ static void process_srcu(struct work_struct *work)
        } else {
                j = jiffies;
                if (READ_ONCE(sup->reschedule_jiffies) == j) {
+                       ASSERT_EXCLUSIVE_WRITER(sup->reschedule_count);
                        WRITE_ONCE(sup->reschedule_count, READ_ONCE(sup->reschedule_count) + 1);
                        if (READ_ONCE(sup->reschedule_count) > srcu_max_nodelay)
                                curdelay = 1;