From: Paul E. McKenney Date: Sat, 21 Dec 2019 19:23:50 +0000 (-0800) Subject: rcutorture: Fix stray access to rcu_fwd_cb_nodelay X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=102c14d2f87976e8390d2cb892ccd14e3532e020;p=linux.git rcutorture: Fix stray access to rcu_fwd_cb_nodelay The rcu_fwd_cb_nodelay variable suppresses excessively long read-side delays while carrying out an rcutorture forward-progress test. As such, it is accessed both by readers and updaters, and most of the accesses therefore use *_ONCE(). Except for one in rcu_read_delay(), which this commit fixes. This data race was reported by KCSAN. Not appropriate for backporting due to this being rcutorture. Signed-off-by: Paul E. McKenney --- diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c index edd97465a0f77..124160a610fa3 100644 --- a/kernel/rcu/rcutorture.c +++ b/kernel/rcu/rcutorture.c @@ -339,7 +339,7 @@ rcu_read_delay(struct torture_random_state *rrsp, struct rt_read_seg *rtrsp) * period, and we want a long delay occasionally to trigger * force_quiescent_state. */ - if (!rcu_fwd_cb_nodelay && + if (!READ_ONCE(rcu_fwd_cb_nodelay) && !(torture_random(rrsp) % (nrealreaders * 2000 * longdelay_ms))) { started = cur_ops->get_gp_seq(); ts = rcu_trace_clock_local();